Thèses sur le sujet « Electrical evoked potentials »
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1
Hocking, Christopher Anthony, et Christopher Hocking@med monash edu au. « Brain electrical activity and automization ». Swinburne University of Technology, 1999. http://adt.lib.swin.edu.au./public/adt-VSWT20051021.110535.
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Novices and experts show distinct differences in the performance of many tasks. Experts may perform a task quickly and accurately with seemingly little attention or effort, whilst novices will perform the same task more slowly and with great effort. The transition from novice to expert performance occurs only after extended practice and has been conceptualized as a transition from controlled to automatic processing, and has been modeled as a reduction in attention or cognitive resources. Alternatively, based on findings relating to learning in the domain of number arithmetic, it has also been modeled as a transition from an algorithmic, or computationally-based process, to the use of memory retrieval.
However, relatively few studies have investigated the changes in brain activity associated with such a transition. In this study, the Steady-State Probe Topography technique was used to investigate differences in the topography of the Steady-State Visual Evoked Potential (SSVEP) between an unpracticed and a well-practiced analogue of number arithmetic, Alphabet arithmetic.
Subjects showed decreases in response time with practice that followed a power law and were suggestive of automatization. During initial, unpracticed performance of the task, processing of the Alphabet Arithmetic equations was characterised by increased SSVEP amplitude and decreased latency in frontal regions, whilst after extended practice, performance was characterised by reduced SSVEP amplitude and increased latency. It is suggested that the frontal activity during the initial, unpracticed stage of the task implicates a role for working memory, whilst the amplitude decrease and latency increase observed in the well-practiced task may reflect a reduction in excitation, consistent with ideas of an improvement in brain efficiency, and possibly an increase in inhibitory processes.
2
Rennie, Christopher. « Modeling the large-scale electrical activity of the brain ». Connect to full text, 2001. http://hdl.handle.net/2123/816.
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Thesis (Ph. D.)--University of Sydney, 2001.Includes published articles. Title from title screen (viewed Apr. 24, 2008). Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the School of Physics, Faculty of Science. Includes bibliography. Also available in print form.
3
Ciorciari, Joseph, et jciorciari@swin edu au. « Topograhic distribution of human brain electrical activity associated with schizophrenia ». Swinburne University of Technology, 1999. http://adt.lib.swin.edu.au./public/adt-VSWT20050610.152013.
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A literature review of the schizophrenia brain electrophysiology was undertaken with specific emphasis placed on the topographical distribution of evoked potentials (EPs). The outcomes of this review suggests that schizophrenia brain electrophysiology, demonstrate some differences, but with a variability reflective of the symptom heterogeneity. The literature associated with the use of attentional tasks while recording EPs, tended to demonstrate some consistency. The methodological issues associated with the EEG and EP recordings may also account for this variability. An evoked potential technique, which has been demonstrated to be sensitive to the changes in cognitive processes associated with attention, is the Steady State Probe Topography (SSPT) technique. The SSPT is a combination of both the Steady State Visual Evoked Potential (SSVEP) and the Probe-ERP paradigm. This technique allows the SSVEP to be measured continuously, is relatively insensitive to artifact, and can display the topographic distribution of the SSVEP measures during the attentional task. The technique employs the use of a sixty-four channel EEG recording system. This consists of a multichannel electrode helmet; multichannel amplifier/filter, task presentation computer and a computer controlled data acquisition system. Software was also developed to analyse the recorded brain electrical activity to produce the SSVEP magnitude and phase versus time series for each electrode site. The topographic distribution of the SSVEP measures associated with specific events during attentional tasks could also be displayed. At the time of the pilot study, this technique had not been applied previously to the study of schizophrenia and therefore warranted further study. Two separate studies are reported; an investigative pilot study and a chronic group study. The pilot SSVEP and schizophrenia study was designed to examine the changes in the SSVEP and its topography, during the performance of a number of attentional or activation tasks to examine the possibility of hypofrontality. The tasks selected for the study were those previously used for the examination of hypofrontality with metabolic imaging techniques; the Continuous Performance Task (CPT) and the Wisconsin Card Sort (WCS). The SSVEP was elicited by a superimposed 13Hz flicker on the visual field, while subjects performed computerised versions of the neuropsychological tasks. Topographical maps of the SSVEP magnitude distribution were then interpolated and displayed as an animated sequence synchronised with particular events occurring during the tasks. In comparison to the male control group, male schizophrenic patients exhibited differences in the SSVEP topography for all tasks, possibly reflecting the deficits in behavioural indices. Overall, the findings indicated that the technique demonstrated some merit for further examination of frontal SSVEP topography in schizophrenia. In a larger study of twenty chronic schizophrenia patients, the frontal topographical distribution of the SSVEP was examined. The earlier pilot study finding of reduced frontal SSVEP amplitude was replicated. The issue of hypofrontality in schizophrenia was applied as a possible interpretation.
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Takeyama, Hirofumi. « Human entorhinal cortex electrical stimulation evoked short-latency potentials in the broad neocortical regions : Evidence from cortico-cortical evoked potential recordings ». Kyoto University, 2020. http://hdl.handle.net/2433/253148.
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Yamao, Yukihiro. « Intraoperative dorsal language network mapping by using single-pulse electrical stimulation ». Kyoto University, 2014. http://hdl.handle.net/2433/188692.
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Tanguenza, Arianna. « Somatosensory Evoked Potentials following somatotopic and non somatotopic upper limb electrical stimulation ». Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019.
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Uno dei principali problemi riscontrati nell’utilizzo di una protesi di arto superiore è la mancanza di feedback sensoriale, che riduce il controllo di movimenti e forza applicata, limitando la percezione della protesi come parte del proprio corpo (embodiment). La stimolazione non invasiva dei nervi mediano e ulnare rappresenta un possibile strumento per la restituzione di feedback somatotopico, cioè percepito sull’arto (mano) fantasma, in alternativa alle procedure invasive che hanno già permesso di ottenere buone performance su alcuni amputati. I correlati neurali della stimolazione del nervo mediano sono stati ampiamente riportati in letteratura, mentre pochi sono i casi in cui si analizzano gli effetti della stimolazione del nervo ulnare o della stimolazione simultanea di due nervi (bipolare). È inoltre necessario tenere in considerazione gli effetti della stimolazione non somatotopica, non riferita alla mano ma localizzata sul sito di stimolazione, in quanto si tratta di un fenomeno “di disturbo” presente anche nella stimolazione somatotopica. Questo elaborato si pone l’obiettivo di caratterizzare i correlati neurali in seguito alla stimolazione elettrica transcutanea (TENS) dei nervi dell’arto superiore. Undici soggetti sono stati sottoposti alla stimolazione dei nervi mediano e ulnare, concorrente alla registrazione del segnale elettroencefalografico (EEG). In un piccolo gruppo è stata effettuata anche la caratterizzazione della stimolazione non somatotopica. I Potenziali Evocati Somatosensoriali (SEPs) sono stati confrontati per ogni condizione di stimolazione. Nell’elaborato vengono discusse le differenze riscontrate e vengono analizzati in dettaglio gli effetti della stimolazione somatotopica, considerata come migliore soluzione per il feedback non invasivo.
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Reeve, Edward M. « Brain electrical activity assessment of concurrent music and event-related potential cognitive tasks / ». The Ohio State University, 1986. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487323583620978.
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Gale, Alan Ian. « Signal processing and modelling of coritcal evoked potentials for feature extraction ». Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/42593.
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Johnson, Mark Ian. « Factors influencing the analgesic effects and clinical efficacy of transcutaneous electrical nerve stimulation (TENS) ». Thesis, University of Newcastle Upon Tyne, 1991. http://hdl.handle.net/10443/539.
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Transcutaneous electrical nerve stimulation (TENS) is a simple, non-invasive technique used in the control of chronic pain. Despite the success of TENS and its continued use for over twenty years, some patients either fail to respond or show only a partial response. Furthermore some patients respond initially to TENS but then become tolerant to its analgesic effects. The reasons for poor response to TENS are unknown; different clinics report widely differing success rates, and information on long-term efficacy is sparse. Furthermore, TENS is still administered on an empirical basis in which the patient determines by trial and error the most appropriate stimulator settings (i. e. electrical characteristics of TENS) to treat his or her particular pain. It is impossible to predict whether an individual patient will respond to TENS or which stimulator settings will be optimal. In an attempt to elucidate these problems, the clinical, electrophysiological, neuropharmacological, psychological and sociological factors that influence the analgesic effects and clinical efficacy of TENS have been examined in this thesis. Three clinical studies were performed. The first (Study 2.1) reviewed the use of TENS since its introduction to Newcastle Pain Relief Clinic in 1979. It was found that 1582 patients have been given a trial of TENS of which 927 (58.6%) continue to use a stimulator on a long-term basis (Study 2.1). The clinical use of TENS by 179 of these patients was examined in-depth (Study 2.2). Although previous literature suggests that TENS is most efficacious for pains of neurogenic (neuropathic) origin, it was found that any type of pain may respond. No relationships were found to exist between the electrical characteristics of TENS (i. e. stimulator settings) used by patients during TENS treatment and the cause and site of pain. However, patients utilised specific pulse frequencies and patterns and consistently used these settings on subsequent treatment sessions (Study 2.3). These clinical studies showed that in this population, 41.4% of patients failed to respond to TENS and half using TENS on a long-term basis achieved less than 50% relief of pain. Thus, a systematic investigation to determine optimal electrical characteristics of TENS was performed. Three experiments were undertaken to examine separately the analgesic effects of different electrical characteristics of TENS (pulse frequency, pulse pattern and stimulation mode) on cold-pressor pain in healthy subjects. The effects of a range of Long Abstract pulse frequencies (10Hz to 160Hz) applied to produce a 'strong but comfortable' electrical paraesthesia within the painful site were measured (Exp. 3.1). It was found that frequencies between 20-80Hz were most effective. However, no differential effects were observed between a range of pulse patterns (continuous, burst, modulation, random; Exp. 3.2). When TENS was applied in burst mode at an intensity sufficient to produce phasic muscle twitches at a site distant yet myotomally related to the site of pain (acupuncture-like TENS) a powerful analgesic effect was observed during and post-stimulation (Exp. 3.3). It is suggested that continuous mode stimulation at 80Hz, producing a 'strong but comfortable' electrical paraesthesia within the painful site, should be the primary TENS treatment choice in the clinic but that in selected cases AL-TENS may be more effective. A number of improvements in stimulator design are suggested. Further experiments were aimed at elucidating the mechanism of TENS effects by investigating the influence of TENS on electrophysiological and neuropharmacological variables. It was found that TENS reduced peak-to-peak amplitudes of the late waveform components (N1P2) of somatosensory evoked potentials (Exp. 4.1) and increased alpha, beta and theta activity of spontaneous EEG in healthy subjects (Exp. 4.2) and/or pain patients (Exp. 4.3). As TENS produced changes in SEPs elicited from non-painful stimuli, and also changes in spontaneous EEG in pain-free subjects, it is suggested that the effects of TENS may be due in part to changes in sensory processing at several levels in the nervous system which may not specific for the perception of pain. The surprising finding that TENS increased peripheral circulating met-enkephalin in chronic pain patients was attributed to a stress-like release although this observation remains to be confirmed using a larger population sample (Exp. 5.1). The results of these experiments suggest that baseline electrophysiological and neuropharmacological variables may be important determinants of individual response to TENS. Thus, a prospective investigation was undertaken on 29 patients who were undergoing a trial of TENS to control chronic pain, in an attempt to identify predictors of patient response. Patient response to TENS was related to baseline SEP amplitudes and spontaneous EEG but was not related to biochemical, psycho-social, personality or pain related factors (Exp. 6.1). Thus, patients with small peak-to-peak amplitudes of the SEP, and low power spectrum of spontaneous EEG showed poor response to TENS (Exp. 6.1). It is suggested that an individual's intrinsic central response pattern to external stimuli may influence response to TENS.
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Yurtkolesi, Mustafa. « Imaging Electrical Conductivity Distribution Of The Human Head Using Evoked Fields And Potentials ». Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609828/index.pdf.
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In the human brain, electrical activities are created due to the body functions. These
electrical activities create potentials and magnetic fields which can be monitored elec-
trically (Electroencephalography - EEG) or magnetically (Magnetoencephalography -
MEG). Electrical activities in human brain are usually modeled by electrical dipoles.
The purpose of Electro-magnetic source imaging (EMSI) is to determine the position,
orientation and strength of dipoles. The first stage of EMSI is to model the human
head numerically. In this study, The Finite Element Method (FEM) is chosen to han-
dle anisotropy in the brain. The second stage of EMSI is to solve the potentials and
magnetic fields for an assumed dipole configuration (forward problem). Realistic con-
ductivity distribution of human head is required for more accurate forward problem
solutions. However, to our knowledge, conductivity distribution for an individual has
not been computed yet.
The aim of this thesis study is to investigate the feasibility of a new approach to
update the initially assumed conductivity distribution by using the evoked potentials
and fields acquired during EMSI studies. This will increase the success of source
localization problem, since more realistic conductivity distribution of the head will be
used in the forward problem. This new method can also be used as a new imaging
modality, especially for inhomogeneities where the conductivity value deviates.
In this thesis study, to investigate the sensitivity of measurements to conductivity
perturbations, a FEM based sensitivity matrix approach is used. The performance
of the proposed method is tested using three different head models - homogeneous
spherical, 4 layer concentric sphere and realistic head model. For spherical head models
rectangular grids are preferred in the middle and curved elements are used nearby
the head boundary. For realistic cases, head models are developed using uniform
grids. Tissue boundary information is obtained by applying segmentation algorithms
to the Magnetic Resonance (MR) images. A paralel computer cluster is employed to
assess the feasibility of this new approach. PETSc library is used for forward problem
calculations and linear system solutions.
The performance of this novel approach depends on many factors such as the head
model, number of dipoles and sensors used in the calculation, noise in the measure-
ments, etc. In this thesis study, a number of simulations are performed to investigate
the effects of each of these parameters. Increase in the number of elements in the
head model leads to the increase in the number of unknows for linear system solu-
tions. Then, accuracy of the solution is improved with increased number of dipoles
or sensors. The performance of the adopted approach is investigated using noise-free
measurements as well as noisy measurements. For EEG, measurement noise decreases the accuracy
of the approach. For MEG, the effect of measurement noise is more pronounced and may lead to a larger
error in tissue conductivity calculation.
11
Aranda, George. « Functional brain electrical activity during affective facial processing in people with schizophrenia ». Swinburne Research Bank, 2008. http://hdl.handle.net/1959.3/36027.
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Thesis (PhD) - Swinburne University of Technology, Brain Sciences Institute, 2008.[Submitted for the degree of] Doctor of Philosophy, Brain Sciences Institute, Swinburne University of Technology - 2008. Typescript. Includes bibliographical references (p. 218-269).
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Kitzmiller, Joseph Paul. « Design, engineering,and evaluation of a novel microgrid electrode array to monitor the electrical activity on the surface of the cerebral cortex ». Connect to this title online, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1084824069.
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Thesis (Ph. D.)--Ohio State University, 2004.Title from first page of PDF file. Document formatted into pages; contains xiv, 82 p.; also includes graphics. Includes bibliographical references (p. 80-82). Available online via OhioLINK's ETD Center
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Sable, Jeffrey J. « Electrical and optical investigations of event-related brain activity in human auditory cortex elicited by rapidly presented tones / ». free to MU campus, to others for purchase, 2003. http://wwwlib.umi.com/cr/mo/fullcit?p3115587.
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Hinic, Vladimir. « Brain computer interface system for communication and robot control based on auditory evoked event-related potentials ». Thesis, University of Ottawa (Canada), 2009. http://hdl.handle.net/10393/28226.
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This study evaluates the suitability of the auditory, specifically spoken words, evoked P300 based Brain-Computer Interface (BCI) for the human-computer symbiotic control of Robotic Sensor Agents (RSA). This study is unique in using auditory evoked P300 for BCI communication and control, contrary to currently established P300 BCI research. The general, elaborate, and multi platform software framework BCIILab was developed as a part of BCI laboratory workbench used specifically in the research. Result of this study shows that it is possible to use auditory P300 based BCI for the complementary control of RSA on the strategic level. The problems encountered in classification during experiments were highlighted and suggestion for future research given.
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Frishkoff, Gwen Alexandra. « Brain electrical correlates of emotion and attention in lexical semantic processing / ». view abstract or download file of text, 2004. http://wwwlib.umi.com/cr/uoregon/fullcit?p3147820.
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Thesis (Ph. D.)--University of Oregon, 2004.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 432-460). Also available for download via the World Wide Web; free to University of Oregon users.
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Wong, Chi Man. « Phase information enhanced steady-state visual evoked potential-based brain-computer interface ». Thesis, University of Macau, 2011. http://umaclib3.umac.mo/record=b2493316.
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Robinson, Rebecca Louise. « Experimental study of electrophysiology using the fEITER system ». Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/experimental-study-of-electrophysiology-using-the-feiter-system(399260d4-6c11-4227-9633-4d76f933e5af).html.
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Within neurophysiology, there is need for improvements to functional brain imaging devices. Neural processing within the brain occurs on milli-second through to second timescales. Currently there are no systems with the sufficient temporal resolution and depth sensitivity. Electrical impedance tomography (EIT) is a technique that offers milli-second imaging, depth sensitivity, portability and low cost. It is already applied routinely in other medical applications such as lung function monitoring and breast imaging. The research presented in this thesis has contributed to the design and development of a 32-electrode EIT system, known as fEITER (functional Electrical Impedance Tomography of Evoked Responses). fEITER has been designed to be a brain imaging device that has a temporal resolution of 100 fps with an overall SNR of greater than 70 dB operating at 10 kHz. In order to carry out human tests using fEITER, the system required applications to the local and national ethics (NRES) as well as safety standards regulation (MHRA). These processes were successfully completed, receiving a 'notice of no objection' for a clinical trial using fEITER at The University of Manchester and Manchester Royal Infirmary. A series of tank tests were analysed as a method of understanding the system performance. The data obtained from human tests showed unique results. The reference data showed a repeating 'saw tooth' that is time-locked to the heart beat of the volunteer, which is a novel observation in medical EIT. Furthermore, the auditory stimuli data showed topographical differences across the scalp with respect to the startle and controlled auditory stimuli. These observations are based on single-event evoked responses, which is unique within the field of evoked potential studies. From the observations reported in this thesis it is plausible that fEITER is measuring voltages changes that are due to the neural processing.
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Farrow, Maree J., et maree farrow@med monash edu au. « Brain electrical activity topography in attention-deficit/hyperactivity disorder ». Swinburne University of Technology, 2003. http://adt.lib.swin.edu.au./public/adt-VSWT20050406.141958.
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Attention-deficit/hyperactivity disorder (ADHD) is a common childhood psychiatric disorder characterized by developmentally inappropriate levels of inattentiveness, impulsivity and hyperactivity. Current theories of ADHD cite evidence from neuropsychological and brain imaging studies suggesting that abnormalities in the structure and function of the frontal lobes and connected brain regions are associated with impaired behavioural inhibition, constituting the primary deficit in ADHD. While most reviewers conclude that neuropsychological studies have failed to find specific deficits in various aspects of attention in ADHD, poor performance on attentional tasks, including the continuous performance task (CPT), is a common finding and previous electrophysiological studies suggest evidence of impaired attentional processing. This study aimed to investigate the cortical activity associated with attentional processes in children with and without ADHD, using steady-state probe topography (SSPT). Seventeen boys diagnosed with ADHD and seventeen age matched control boys participated. Changes in the amplitude and latency of the steady-state visually evoked potential (SSVEP) associated with correct responses to targets in the �X� and �AX� versions of the CPT were examined. At critical time points in both tasks, the control group demonstrated SSVEP changes suggesting increased activation and increased speed of neural processing. These effects occurred predominantly in medial frontal, right prefrontal, right parietal and occipital regions, suggesting enhanced activity in regions previously shown to be involved in attentional processes. The ADHD group demonstrated much smaller increases in activation and processing speed in frontal regions and predominantly reduced activation and slower processing in parieto-occipital regions. Group differences suggesting reduced activity in the ADHD group were observed in response to the presentation of both cues and targets, as well as in the intervals leading up to target presentation, especially in the cued CPT-AX. These results suggest that processing of task relevant stimuli as well as preparatory and motor processes may be associated with dysfunctional activation of brain networks of attention in ADHD, involving deficits in both frontal and parietal cortical regions. These regions may also be involved in the maintenance of information required for correct task performance and the results also suggest possible deficits in these processes in ADHD. The findings are consistent with others of reduced activation and cognitive deficits in ADHD involving these brain regions and networks, and with the idea that ADHD may be associated with a diminished ability to regulate levels of arousal and activation appropriate to task demands.
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Qi, Hong. « Pattern Recognition and ERP Waveform Analysis Using Wavelet Transform ». PDXScholar, 1993. https://pdxscholar.library.pdx.edu/open_access_etds/4623.
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Wavelet transform provides an alternative to the classical Short-Time Fourier Transform (STFT). In contrast to the STFT, which uses a single analysis window, the Wavelet Transform uses shorter windows at higher frequencies and longer windows at lower frequencies. For some particular wavelet functions, the local maxima of the wavelet transform correspond to the sharp variation points of the signal. As an application, wavelet transform is introduced to the character recognition. Local maximum of wavelet transform is used as a local feature to describe character boundary. The wavelet method performs well in the presence of noise. The maximum of wavelet transform is also an important feature for analyzing the properties of brain wave. In our study, we found the maximum of wavelet transform was related to the P300 latency. It provides an easy and efficient way to measure P300 latency.
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Houlden, David Allen. « A comparison of descending evoked potentials and muscle responses after transcranial magnetic stimulation and skull base electrical stimulation in awake human subjects ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0006/NQ27955.pdf.
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Lin, Xueming. « ERP Analysis Using Matched Filtering and Wavelet Transform ». PDXScholar, 1994. https://pdxscholar.library.pdx.edu/open_access_etds/5065.
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Event related potentials (ERP's) carry very important information that relates to the performance of the brain functions of the human being. Further studies have identified that one component, in particular, P 300, is affected by the memory process. Matched filter is used to improved the SNR of signal ERP' s. We use the output of the matched filter to distinguish the difference of the waveforms between normal subjects and memory-impaired subjects. In our study, we found that the peak values of the matched filtering output were different between normal subjects and memoryimpaired subjects. Also, as an application, wavelet transform is introduced to the ERP analysis. Local maximum of wavelet transform was used as a local feature to find the relationship between the sharp variation points and the memory process. A comparison between matched filtering and wavelet transform was made and also the correlation coefficients of the peaks and sharp variation points are calculated to find the relationship between the important moments in a memory process.
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Krupenia, Stas Simon. « An event related potential (ERP) study of symptomatic and asymptomatic adults with attention deficit hyperactivity disorder (ADHD) ». University of Western Australia. School of Psychology, 2003. http://theses.library.uwa.edu.au/adt-WU2003.0035.
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This study recorded Event Related Potentials (ERPs) during completion of a Continuous Performance Task (CPT) in order to identify the contribution of response inhibition, working memory, and response monitoring to the pattern of hyperactive and impulsive and inattentive behaviour observed in patients with Attention Deficit Hyperactive Disorder (ADHD). Four ERP components, Nogo N2, Nogo P3, Go P3, and the ERN were examined and compared using a symptomatic and asymptomatic ADHD sample, and a healthy control group. The Nogo N2 had the expected frontal scalp distribution and was affected by changes to inhibitory demands. It was also suggested that this component was not wholly determined by inhibitory processing and may have been influenced by differing presentation rates of the Go stimulus, a template matching process or an in-depth response strategy. Source localisation analysis suggested a right frontal generator for this component. The Nogo P3 had the expected central distribution and had equal amplitude for those participants that were more efficient at inhibiting behaviours compared to those participants that were less efficient inhibitors. Contrary to expectations, the Nogo P3 was not affected by increasing the inhibitory demands of the task and was suggested as being a less reliable indicator of response inhibition in the present study. The Go P3 had the expected centro-parietal distribution, and appeared to provide a reliable index of working memory. Response inhibition and working memory were not impaired in the sample of symptomatic and asymptomatic ADHD adults used in this study. The symptomatic group elicited a slightly enhanced ERN compared to the asymptomatic and control groups, indicating that deficits in response monitoring may contribute to the pattern of problematic behaviour observed in people with ADHD.
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Vincent, Marion. « Measuring the effects of direct electrical stimulation during awake surgery of low grade glioma ». Thesis, Montpellier, 2017. http://www.theses.fr/2017MONTS054.
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La "chirurgie éveillée du cerveau" consiste à retirer des tumeurs cérébrales infiltrantes (gliomes de bas grade, GIBG) à progression lente chez un patient éveillé. Une cartographie anatomo-fonctionnelle du cerveau est réalisée par stimulation électrique directe (SED) des zones proches de la tumeur afin de discriminer les aires cérébrales fonctionnelles de celles qui ne le sont plus. Les effets inhibiteurs de la stimulation sont mis en évidence par les tests neuropsychologiques réalisés par le patient lors de la chirurgie. Cependant, la SED est paramétrée de manière totalement empirique bien qu’utilisée de façon standardisée. De plus, si ses effets comportementaux sont mis en avant, ses effets électrophysiologiques restent plus méconnus. La conservation de la relation entre électrophysiologie (potentiel évoqué, PE) et comportement (fonction) est cruciale lors de chirurgies des GIBG : l’analyse des PE en temps réel permettrait une identification de ces relations au cours même de la chirurgie.Pour cela, nous avons réalisé des enregistrements peropératoires de l’activité électro-corticographique (ECoG) du cortex (CPP, n° ID-RCB : 2015-A00056-43). L’étude de ces enregistrements a permis de mesurer les effets electrophysiologiques de la SED corticale et sous-corticale, en évaluant la réponse du cerveau à la stimulation au travers des PE. Une chaine d'acquisition spécifique à la mesure de l'ECoG a été développée afin de pouvoir à terme mesurer et visualiser les PE en temps réel. De plus, un algorithme de post-traitement a été implémenté afin de réduire la contamination du signal par l’artefact de stimulation.Mieux comprendre les mécanismes sous-jacents à la SED, notamment au travers de la mesure des réponses électrophysiologiques, doit permettre de proposer des protocoles peropératoires plus objectifs afin d'améliorer la planification chirurgicale et la qualité de vie des patientsThe ‘Awake brain surgery’ consists in removing some slow-growing infiltrative brain tumor (low grade glioma, LGG) in a patient, to delay its development while preserving the functions. An anatomo-functional mapping of the brain is performed by electrically stimulating brain areas near the tumor to discriminate functional versus nonfunctional areas. The inhibitory effects of this direct electrical stimulation (DES) are evidenced by the neuropsychological tests undergone by the patient during the tumor resection. However, the DES parameters are empirically set even though its use is standardised. Moreover, even if its behavioural effects are well known, its electrophysiological effects have been partially depicted.Preserving the relationship between electrophysiology (evoked potential, EP) and behaviour (function) is crucial in LGG surgery.Intra-operative electrocorticographic recordings (ECoG) of the brain activity were thus performed (CPP, n° ID-RCB : 2015-A00056-43). The electrophysiological effects of cortical and subcortical DES on brain activity have been highlighted, by assessing the response of the brain to the stimulation through EP recordings analysis. A new acquisition set-up has also been specifically developed for ECoG recordings in order to measure and eventually visualise the EP in real-time. Furthermore, a post-processing algorithm has been implemented to reduce the signal disturbances induced by the stimulation artefact.A better understanding of the underlying DES mechanisms, in particular through the measurement of electrophysiological responses, should enable designing more perfected protocols in order to improve the surgical planning, and quality of life of the patients
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Beuriat, Pierre-Aurélien. « Mapping the anatomo-functional organization of human sensorimotor system : a multi-modal approach ». Thesis, Lyon, 2019. http://www.theses.fr/2019LYSE1246/document.
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Le but de cette thèse était d'étudier l'organisation anatomo-fonctionnelle du système sensorimoteur humain et la façon dont les mouvements volontaires sont produits et contrôlés. Avec le développement de l’imagerie cérébrale, des méthodes de corrélation anatomo-clinique et de stimulation électrique directe cérébrale, de nombreuses avancées scientifiques ont pu être réalisée. Ces trois approches complémentaires ont été utilisé dans cette thèse afin d’améliorer la compréhension de l’organisation sensorimotrice cérébrale. Dans la première étude (soumise à publication), nous avons montré que la chirurgie cérébrale éveillée utilisant la stimulation électrique directe est une procédure sûre et efficace chez les enfants afin de réduire le déficit neurologique postopératoire. L'approche améliore la précision de la détection des zones éloquentes, avec une bonne tolérance neuropsychologique et psychologique. Une évaluation psychologique et neuropsychologique est essentielle. Dans une deuxième série de deux études, nous avons montré que la partie dorso-postérieure dorsal du cortex pariétal (DPPr) est une structure clé dans l'organisation complexe du mouvement manuel fin chez l'homme à travers la mise en oeuvre d'une boucle sensori-parieto-motrice.La première étude (publiée, Current Biology 2018) montre que la stimulation électrique directe d’une region corticale focale dans la partie dorso-postérieure du cortex pariétal entraine l’inhibition de la production du mouvement manuel, c’est-à-dire bloque l'initiation et la réalisation de ce dernier, sans produire de contraction musculaire ni de sensation consciente de mouvement. Dans la seconde étude (en cours de soumission), nous avions pour objectif d'identifier précisément les bases anatomiques du circuit parietal inhibiteur précédemment décrit. Grâce à la tractographie de diffusion (DTI), nous avons réussi à isoler des projections ipsilatérales spécifiques reliant les sites d’inhibition du DPPr, retrouvés dans la première étude, avec la zones dévolues au contrôle distal fin dans les cortex primaires moteur (M1) et sensoriel (S1). Ces données montrent que la boucle pariétale inhibitrice est directe depuis S1 vers DPPr vers M1 (même s'il n'est pas possible d'exclure l'existence d'échanges bidirectionnels entre ces aires). Dans la dernière étude (en cours de soumission), nous nous sommes intéressé à une structure motrice fondamentale, qui supporte 50 % des invasions tumorales chez l'enfant : le cervelet. Il s'agissait de déterminer si les lésions précoces étaient oui ou non prédictives d'une récupération déficitaire à long terme après prise en compte des covariables les plus critiques. Nous avons mesuré la récupération fonctionnelle à long terme chez 3 groupes survivants de lésion de la fosse postérieure. Les 3 groupes étaient comparables en ce qui concerne leurs caractéristiques tumorales mais opérés à différents âges : jeune (≤ 7 ans), moyen (> 7 ans et ≤ 13 ans) et tardif (> 13 ans). La qualité de vie (échelles cliniques : Health-related Quality of Life -hrQol- et Performance Status -PS-), les performances motrices (ataxie -ICARS- et motricité fine -Pegboard-) et cognitif (quotient intellectuel -FSIQ-) furent mesurés. L'âge précoce lors de la chirurgie, une lésion des noyaux profonds cérébelleux et la nécessité d'une radiothérapie postopératoire révélèrent une influence significativement négative et indépendante sur la récupération à long terme des participants. Ces résultats confirment l'existence d'une période critique de développement au cours de laquelle la "machine à apprendre" cérébelleuse revêt une importance crucialeThe aim of the thesis was to investigate the mapping of the anatomofunctional organization of the human sensorimotor system and how volutional movements of human are produced and controlled. Neuroimaging and especially DTI, fine anatomo-functional observation in patient and direct electrical stimulation were considered. This multi-modal approach permitted to improve our understanding of sensorimotor organization in humans. In the first study, we showed that awake brain surgery with the use of direct electrical stimulation is a safe and efficient procedure in children in order to decrease post-operative neurological deficit. It improves the accuracy of detecting eloquent area, with a good tolerance from a neuropsychological and psychological aspect. Age-adapted neuropsychologic preparation may enable offering ABS even to younger children on an individual basis. In a second series of two studies, we showed that the dorso-posterior part of the parietal cortex is a key structure in the complex organization of movement in human with a S1-DPPr-M1 loop. In the first study, direct electrical stimulation of focal cortical site in the dorso-posterior part of the parietal cortex triggered inhibition of movement production and blocked ongoing movement without producing muscle contraction or conscious movement sensation. In the second study, we aimed to find a direct projection from the PRR, defined in the first study (Desmurget et al., 2018), to the primary motor cortex and the primary somatosensory cortex. Thanks to the DTI state-of-the-art tractography, we succeeded in finding such major ipsilateral streamlines projecting in the well-known hand knob region giving new insights of the white matter structures involved in the inhibition of volitional hand movements. These observations confirm clinical per-operative data showing that stimulating the counterpart of PRR in humans can disrupt hand movements ipsilaterally, irrespective of the hemisphere. Moreover, our results shed light on the implication of the PRR for the volitional hand sensorimotor operating behavior. In the last study, we investigate the impact of early cerebellar damage on long-term functional recovery in 3 groups of posterior fossa survivors, comparable with respect to their tumoural characteristics but operated at different ages: young (≤ 7 years), middle (> 7 years and ≤ 13 years) and old (> 13 years). Daily (Health-related Quality of Life -hrQol-, Performance Status -PS-), motor (International Cooperative Ataxia Rating Scale -ICARS-, Pegboard Purdue Test -PegBoard-) and cognitive (Full Scale Intelligence Quotient -FSIQ-) functioning were measured. Early age at surgery, lesion of deep cerebellar nuclei and post-operative radiotherapy had a significant, independent negative influence on long term recovery. These results support the existence of an early critical period of development during which the cerebellar "learning machine" is of critical importance
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Sonkajärvi, E. (Eila). « The brain's electrical activity in deep anaesthesia:with special reference to EEG burst-suppression ». Doctoral thesis, Oulun yliopisto, 2015. http://urn.fi/urn:isbn:9789526209722.
Texte intégralRésumé :
Abstract Several anaesthetics are able to induce a burst-suppression (B-S) pattern in the electroencephalogram (EEG) during deep levels of anaesthesia. A burst-suppression pattern consists of alternating high amplitude bursts and periods of suppressed background activity. All monitors measuring the adequacy of anaesthesia recognize the EEG B-S as one criterion. A better understanding of EEG burst-suppression is important in understanding the mechanisms of anaesthesia. The aim of the study was to acquire a more comprehensive understanding of the function of neural pathways during deep anaesthesia. The thesis is comprised of four prospective clinical studies with EEG recordings from 64 patients, and of one experimental study of a porcine model of epilepsy with EEG registrations together with BOLD fMRI during isoflurane anaesthesia (II). In study I, somatosensory cortical evoked responses to median nerve stimulation were studied under sevoflurane anaesthesia at EEG B-S levels. In study III, The EEGs of three Parkinson`s patients were observed to describe the characteristics of B-S during propofol anaesthesia using scalp electrodes and depth electrodes in the subthalamic nucleus. In study IV, EEG topography was observed in 20 healthy children under anaesthesia mask induction with sevoflurane. Twenty male patients were randomized to either controlled hyperventilation or spontaneous breathing groups for anaesthesia mask induction with sevoflurane in study V. EEG alterations in relation to haemodynamic responses were examined in studies IV and V. Somatosensory information reached the cortex even during deep anaesthesia at EEG burst-suppression level. Further processing of these impulses in the cortex was suppressed. The EEG slow wave oscillations were synchronous over the entire cerebral cortex, while spindles and sharp waves were produced by the sensorimotor cortex. The development of focal epileptic activity could be detected as a BOLD signal increase, which preceded the EEG spike activity. The epileptogenic property of sevoflurane used at high concentrations especially during hyperventilation but also during spontaneous breathing together with heart rate increase, was confirmed in healthy children and male. Spike- and polyspike waveforms concentrated in a multifocal manner frontocentrallyTiivistelmä Useat anestesia-aineet pystyvät aiheuttamaan aivosähkökäyrän (EEG) purskevaimentuman syvän anestesian aikana. Purskevaimentuma koostuu EEG:n suuriamplitudisten purskeiden sekä vaimentuneen taustatoiminnan vaihtelusta. Kaikkien anestesian syvyyttä mittaavien valvontalaitteiden toiminta perustuu osaltaan EEG:n purskevaimentuman tunnistamiseen. Tämän ilmiön parempi tunteminen on tärkeää anestesiamekanismien ymmärtämiseksi. Tutkimuksen päämääränä oli saada kattavampi käsitys hermoratojen toiminnasta syvässä anestesiassa. Väitöskirjatyö koostuu neljästä prospektiivisesta yhteensä 64 potilaan EEG-rekisteröinnit sisältävästä tutkimuksesta sekä yhdestä kokeellisen epilepsiatutkimuksen koe-eläintyöstä, jossa porsailla käytettiin isofluraanianestesiassa sekä EEG-rekisteröintejä sekä että magneettikuvantamista (fMRI) samanaikaisesti (II). Ensimmäisessä osatyössä tutkittiin keskihermon stimulaation aiheuttamia somatosensorisia herätepotentiaaleja aivokuorella EEG:n purskevaimentumatasolla sevofluraanianestesian aikana. Kolmannessa osatyössä selvitettiin propofolianestesian aiheuttamaa EEG:n purskevaimentumaa kolmelta Parkinsonin tautia sairastavalta potilaalta käyttäen sekä pintaelektrodien että subtalamisen aivotumakkeen syväelektrodien rekisteröintejä. Neljännessä osatyössä tutkittiin EEG:n topografiaa 20:llä terveeellä lapsella indusoimalla anestesia sevofluraanilla. Kaksikymmentä miespotilasta nukutettiin sevofluraanilla ja heidät satunnaistettiin joko kontrolloidun hyperventilaation tai spontaanin hengityksen ryhmiin osatyössä V. EEG-muutoksia sekä niiden yhteyttä verenkiertovasteisiin selviteltiin molemmissa osatöissä IV ja V. Omasta kehosta tuleviin tuntoärsykkeisiin liittyvä somatosensorinen informaatio saavutti aivokuoren myös syvässä EEG:n purskevaimentumatasoisessa anestesiassa. Impulssien jatkokäsittely aivokuorella oli kuitenkin estynyt. EEG:n hidasaaltotoiminta oli synkronista koko aivokuoren alueella, sen sijaan unisukkulat ja terävät aallot paikantuivat sensorimotoriselle aivokuorelle. Paikallisen epileptisen toiminnan kehittyminen oli mahdollista havaita jo ennen piikikkäiden EEG:n aaltomuotojen ilmaantumista edeltävänä BOLD-ilmiöön liittyvänä aivoverenkierron lisääntymisenä. Sevofluraanin epileptogeenisyys varmistui erityisesti hyperventilaation, mutta myös spontaanin hengityksen yhteydessä ja näihin liittyi sykkeen nousu sekä terveillä lapsilla että miehillä. Piikkejä ja monipiikkejä käsittävien aaltomuotojen keskittymistä esiintyi otsalohkon keskialueilla
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Lemaréchal, Jean-Didier. « Estimation des propriétés dynamiques des réseaux cérébraux à large échelle par modèles de masse neurale de potentiels évoqués cortico-corticaux Comparison of two integration methods for dynamic causal modeling of electrophysiological data. NeuroImage An atlas of neural parameters based on dynamic causal modeling of cortico-cortical evoked potentials ». Thesis, Université Grenoble Alpes, 2020. http://www.theses.fr/2020GRALS007.
Texte intégralRésumé :
Ce travail de thèse porte sur la modélisation des potentiels évoqués cortico-corticaux (PECCs) induits par stimulation électrique intracérébrale lors de procédures de chirurgie de l’épilepsie en stéréo-électroencéphalographie. Nous utilisons pour cela des modèles de masse neurale de type modèles causaux dynamiques (Dynamic causal modeling, DCM).Dans un premier temps, nous démontrons l'importance d'utiliser une technique d'intégration précise pour résoudre le système d'équations différentielles formalisant la dynamique du modèle (Lemaréchal et al., 2018), en particulier pour une estimation précise des paramètres neuronaux du modèle.Dans une seconde étude, nous développons cette méthodologie pour l'appliquer aux PECCs de la base de données du projet F-TRACT. Les délais et les vitesses de propagation axonale entre régions cérébrales ainsi que les constantes de temps synaptiques locales sont estimés et projetés sur des parcellisations corticales validées par la communauté internationale en neuroimagerie. Le nombre important de jeux de données utilisés dans cette étude (>300) permet en particulier de mettre en évidence des différences de propriétés dynamiques de connectivité en fonction de l'âge des populations considérées (Lemaréchal et al., soumis).Enfin, le dernier travail montre comment, dans le contexte Bayésien de DCM, un atlas de connectivité peut servir à améliorer la spécification et l'estimation d'un modèle de masse neurale pour l’explication de données électrophysiologiques de surface de type électroencéphalographique ou magnétoencéphalographique, en fournissant des distributions a priori sur ses paramètres de connectivité.Dans l'ensemble, cette thèse propose de nouvelles estimations des propriétés dynamiques des interactions cortico-corticales. Grâce à la publication et à la mise à disposition de nouveaux atlas regroupant ces propriétés neuronales, les résultats générés peuvent dès à présent servir à une meilleure spécification et une estimation plus précise de modèles neuronaux de cerveau entierThis thesis work aims at modeling cortico-cortical evoked potentials (CCEPs) induced by intracortical direct electrical stimulation in epileptic patients being recorded with stereo-electroencephalography during epilepsy surgery. Neural mass models implemented within the dynamic causal modeling (DCM) framework are used for this purpose.We first demonstrate the importance of using an accurate integration scheme to solve the system of differential equations governing the global dynamics of the model, in particular to obtain precise estimates of the neuronal parameters of the model (Lemaréchal et al., 2018).In a second study, this methodology is applied to a large dataset from the F-TRACT project. The axonal conduction delays and speeds between brain regions, as well as the local synaptic time constants are estimated and their spatial mapping is obtained based on validated cortical parcellation schemes. Interestingly, the large amount of data included in this study allow to highlight brain dynamics differences between the young and the older populations (Lemaréchal et al., submitted).Finally, in the Bayesian context of DCM, we show that an atlas of connectivity can improve the specification and the estimation of a neural mass model, for electroencephalographic and magnetoencephalographic studies, by providing a priori distributions on the connectivity parameters of the model.To sum up, this work provides novel insights on dynamical properties of cortico-cortical interactions. The publication of our results in the form of an atlas of neuronal properties already provides an effective tool for a better specification of whole brain neuronal models
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Garrastacho, Octavio Gabriel. « A New Microprocessor-Controlled Stimulator for Visual Evoked Potential Acquisition ». FIU Digital Commons, 1996. https://digitalcommons.fiu.edu/etd/3592.
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The goal of this study was to develop two computer-controlled visual evoked potential (VEP) stimulators. The first device employs a 12 x 12 matrix of 5 mm square Light Emitting Diodes (LEDs) and is housed in an 8 x 8 utility box structure. The second device employs two 8x8 matrices of 3 mm square LEDs, each housed in one eyepiece of a goggle-like structure. A quantitative comparison of the performance of these stimulators was carried out in terms of absolute and interpeak latencies, signal-to-noise ratio (SNR) and cross-correlation between sequential responses obtained from them. Six normal adult subjects were involved in the comparison. Data were acquired from monocular full-field stimulation. The comparison emphasizes potential advantages of the newer, goggle- mounted stimulator.
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Franck, Kevin H. « The electrically evoked whole-nerve action potential : fitting applications for cochlear implant users / ». Thesis, Connect to this title online ; UW restricted, 1999. http://hdl.handle.net/1773/8241.
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Kobayashi, Katsuya. « Different Mode of Afferents Determines the Frequency Range of High Frequency Activities in the Human Brain : Direct Electrocorticographic Comparison between Peripheral Nerve and Direct Cortical Stimulation ». Kyoto University, 2015. http://hdl.handle.net/2433/202676.
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Usami, Kiyohide. « Sleep modulates cortical connectivity and excitability in humans : direct evidence from neural activity induced by single-pulse electrical stimulation ». Kyoto University, 2015. http://hdl.handle.net/2433/202800.
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Doeltgen, Sebastian Heinrich. « The Effects of Neuromuscular Electrical Stimulation of the Submental Muscle Group on the Excitability of Corticobulbar Projections ». Thesis, University of Canterbury. Communication Disorders, 2009. http://hdl.handle.net/10092/2857.
Texte intégralRésumé :
Neuromuscular electrical stimulation (NMES) has become an increasingly popular rehabilitative treatment approach for swallowing disorders (dysphagia). However, its precise effects on swallowing biomechanics and measures of swallowing neurophysiology are unclear. Clearly defined NMES treatment protocols that have been corroborated by thorough empirical research are lacking. The primary objective of this research programme was therefore to establish optimal NMES treatment parameters for the anterior hyo-mandibular (submental) musculature, a muscle group that is critically involved in the oral and pharyngeal phases of swallowing. Based on previous research, the primary hypothesis was that various NMES treatment protocols would have differential effects of either enhancing or inhibiting the excitability of corticobulbar projections to this muscle group. The research paradigm used to test this hypothesis was an evaluation of MEP amplitude and onset latency, recorded in the functional context of volitional contraction of the submental musculature (VC) and contraction of this muscle group during the pharyngeal phase of volitional swallowing (VPS, volitional pharyngeal swallow). Outcome measures were recorded before and at several time points after each NMES treatment trial. This methodology is similar to, but improved upon, research paradigms previously reported. Changes in corticobulbar excitability in response to various NMES treatment protocols were recorded in a series of experiments. Ten healthy research participants were recruited into a study that evaluated the effects of event-related NMES, whereas 15 healthy research participants were enrolled in a study that investigated the effects of non-event-related NMES. In a third cohort of 35 healthy research participants, task-dependent differences in corticobulbar excitability were evaluated during three conditions of submental muscle contraction: VC, VPS and submental muscle contraction during the pharyngeal phase of reflexive swallowing (RPS, reflexive pharyngeal swallowing). Event-related NMES induced frequency-depended changes in corticobulbar excitability. NMES administered at 80 Hz facilitated MEP amplitude, whereas NMES at 5 Hz and 20 Hz inhibited MEP amplitude. No changes were observed after NMES at 40 Hz. Maximal excitatory or inhibitory changes occurred 60 min post-treatment. Changes in MEP amplitude in response to event-related NMES were only observed when MEPs were recorded during the VC condition, whereas MEPs recorded during the VPS condition remained unaffected. Non-event-related NMES did not affect MEP amplitude in either of the muscle contraction conditions. Similarly, MEP onset latencies remained unchanged across all comparisons. MEPs were detected most consistently during the VC contraction condition. They were less frequently detected and were smaller in amplitude for the VPS condition and they were infrequently detected during pre-activation by RPS. The documented results indicate that event-related NMES has a more substantial impact on MEP amplitude than non-event-related NMES, producing excitatory and inhibitory effects. Comparison of MEPs recorded during VC, VPS and RPS suggests that different neural networks may govern the motor control of submental muscle activation during these tasks. This research programme is the first to investigate the effects of various NMES treatment protocols on the excitability of submental corticobulbar projections. It provides important new information for the use of NMES in clinical rehabilitation practices and our understanding of the neural networks governing swallowing motor control.
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Chan, Ping-hon, et 陳秉漢. « Significance of latency change, amplitude change in intra-operative motor evoked potential by transcranial electrical stimulation duringsupratentorial craniotomy in predicting surgical outcome ». Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B45010663.
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Chan, Ping-hon. « Significance of latency change, amplitude change in intra-operative motor evoked potential by transcranial electrical stimulation during supratentorial craniotomy in predicting surgical outcome / ». View the Table of Contents & ; Abstract, 2006. http://sunzi.lib.hku.hk/hkuto/record/B3658647X.
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Chiou, Li-Kuei. « The effect that design of the Nucleus Intracochlear Electrode Array and age of onset of hearing loss have on electrically evoked compound action potential growth and spread of excitation functions ». Diss., University of Iowa, 2016. https://ir.uiowa.edu/etd/3060.
Texte intégralRésumé :
The purpose of this study was to investigate how design changes in Cochlear Nucleus cochlear implants (CIs) (CI24M, CI24R, CI24RE and CI422) affected electrode impedance and ECAP measures, and to determine if these design changes affected post-lingually deafened adults and children with congenital hearing loss in a similar way.
Results of this study showed that electrode impedance was inversely related to the area of the electrode contacts in the array: lowest for the full-banded CI24M CI and highest for adults who used the CI422 device which has the smallest electrode contacts of all four devices. The noise floor of the NRT system likely plays a significant role in the finding that CI users with older devices (the CI24M, and CI24R CIs) had higher ECAP thresholds than individuals with the CI24RE electrode array. The position of the electrode array in the cochlea was also found to have a significant effect on ECAP measures. CI users with modiolar hugging (the CI24R and CI24RE CIs) electrode arrays were found to have lower ECAP thresholds than CI users whose electrode arrays were seated more laterally in the cochlear duct (e.g. the CI24M and CI422 implants). The position of the electrode contacts relative to the modiolus of the cochlea was found to be related to slope of the ECAP growth functions. The lowest slopes were found in CI24RE users. It also had a significant impact on the width of the channel interaction function. Electrode arrays seated further from the modiolus have significantly more channel interaction than electrode arrays that hug the modiolus of the cochlea.
Differences between results recorded from post-lingually deafened adults and children with congenital hearing loss were minimal. The difference only reflected on the ECAP slopes. Slopes in children with congenital hearing loss were significantly steeper than those recorded from adults. This may indicate that children with congenital hearing loss may have better neural survival than adults with acquired hearing loss.
In conclusion, the results of the current study show evidence of the effects of variations in design and function of the implanted components of the Nucleus CI. Perhaps the most significant finding from the current data set is that electrode arrays located closer to the modiolus of the cochlea have lower thresholds and exhibit less channel interaction than electrode arrays that are positioned more laterally. An argument could be made that lower stimulation levels and less channel interaction may result in better outcomes and/or longer battery life. For CI candidates who do not have significant residual acoustic hearing, the CI24RE implant might be a better choice than the more recently introduced CI422 electrode array.
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VIGANO', LUCA. « DIRECT ELECTRICAL STIMULATION OF PRIMARY MOTOR AND FRONTAL PREMOTOR REGIONS : MAPPING AND PRESERVING NETWORKS FOR HAND MOTOR CONTROL DURING BRAIN TUMOUR RESECTION ». Doctoral thesis, Università degli Studi di Milano, 2020. http://hdl.handle.net/2434/707523.
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This PhD project was funded by EDEN2020 (Enhanced Delivery Ecosystem for Neurosurgery in 2020). Brain disease represent a cost about 800 billion euros per year in Europe and outcome of treatment is demonstrated to critically depend on the knowledge of functional anatomy and its preservation. By combining pre-operative MRI and diffusion-MRI imaging, intra-operative ultrasounds, robotic assisted catheter steering, brain diffusion modelling and a robotics assisted neurosurgical robot (the Neuromate), EDEN2020 aims at realizing an integrated technology platform for minimally invasive neurosurgery which will provide a significative step change in treatment of brain disease. To date, neurosurgical instruments for diagnostic and therapy (drugs infusion) are inserted via rigid cannulas. This represents a primary technological limitation of treatment with direct consequences in patient’s post-operative outcome, since the insertion of rigid cannulas cannot be planned along procedure-optimised trajectories which take into account tissue microstructures and respect the bundles’ topographical anatomo-functional organisation. To bridge this gap, main aim of EDEN2020 is to engineer a steerable catheter for chronic neuro-oncological disease than can be robotically guided and kept in situ for extended period, which insertion can be tailored on clinical conditions and individual anatomy.
The correct trajectory and final positioning of a catheter must be planned and guided through the brain structures by the knowledge of the anatomo-functional organization of the neural circuits subserving the essential motor and cognitive functions to avoid lesions resulting in permanent deficits impacting on the quality of life of patients. In addition, since the diffusivity is enhanced when it follows the white matter pathways belongings to the network in which an individual tumour has grown, as showed by data generated by EDEN consortium, these circuits became the target of the drug. In EDEN animal trials (ovine model), the circuit targeted for delivery was the corticospinal tract, due to the anatomical restriction imposed by the sheep brain. In humans, this descending system, which is essential for everyday life activities allowing the skilled use of the hand (i.e. the ability to manipulate objects and tools), has a much higher level of complexity and its functional organisation has not yet been described in detail as in other animal models. The complexity of the neural organization underlying motor control of hand gestures in humans results in a dramatic degree of freedom, but at the same time in a poor ability to recover after lesions. When this connectivity is infiltrated by a tumour and thus became the possible target of drug delivery devices (EDEN), its complexity must be taken into consideration to avoid the onset of deficits.
The great majority of brain tumours occurs in the frontal lobe and, particularly Low Grade Gliomas (LGGs), develop close or within the cortical but mostly subcortical structures involved in motor control. Therefore, to track safely the entrance and the trajectory of catheters, a reference atlas of the neural circuitry controlling hand movement is mandatory to identify which cortical and subcortical areas must not be lesioned to avoid permanent inability.
Based on this premises, this PhD project investigated, with a multidisciplinary approach, the frontal networks subserving hand function to provide a frame for understanding the connectivity involved in hand skilled movements, which became a possible target for drug delivery in tumours developing in primary motor and/or pre-motor regions.
The skilled use of the hand is allowed by the high level of human sensorimotor control implemented by the corticospinal system, particularly developed in primates, connecting distant and functionally different areas via subcortical bundles and finally acting on the spinal cord with a huge bundle of descending fibres. This complex network computes the sensory information related to the goal of the action to shape the appropriate motor command for motoneurons, the final common path to muscles. Non-human primate studies have demonstrated that the main motor output of the corticospinal tract is the primary motor cortex (M1), which act on the spinal motoneurons, in producing voluntary hand and finger movements. The monkey M1 has recently been demonstrated to represent an anatomo-functional non-unitary sector, subdivided in a caudal region dense with cortico-motoneuronal cells and a rostral sector with few monosynaptic connections to alpha-motoneurons and/or with slower projections to the spinal cord. To control and execute skilled hand movements, M1 is highly interconnected with other frontal and parietal cortical pre-motor regions, with subcortical structures such as the basal ganglia and with the cerebellum. A precise description of the human circuitry allowing for realization of dextrous hand movement is still missing in the human, as the electrophysiological and anatomical experimental approaches developed in animal models cannot be performed (i.e. intracortical microstimulation, neuronal tracing, lesion studies etc.). The unique setting of brain tumour resection with the brain mapping technique gives a great opportunity to use clinical data to evaluate neural networks in humans. In this setting, during surgical resection, Direct Electrical Stimulation (DES) is applied onto the exposed cortical and subcortical areas in order to identify the eloquent sites, i.e. where DES elicits motor responses, thus individuating the structures directly acting on the motor descending pathways, or induces transient impairment of the execution of a task, due to its interference with the physiological activity of the stimulated area. This approach allows for the extension of the resection of the tumour beyond its boundaries, increasing the patients’ survival while preserving their functional integrity. As has emerged by recent publications of our group, among the different stimulation paradigms available for intraoperative monitoring, the high frequency stimulation (‘the pulse technique’), which elicits motor evoked potentials (MEPs), is the most reliable paradigm for mapping the descending fibres originating form primary and non-primary motor areas, also in lesions infiltrating M1, while long and short-range fronto-parietal premotor pathways are well identified when low frequency stimulation (‘the Penfield technique’) is applied while the patient is performing a dedicated object manipulation task, clearly interfering with its performance. With a multidisciplinary approach, by combining electrophysiological data with virtual anatomical dissections by means of high angular resolution diffusion imaging (HARDI) tractography we correlated the functional properties of the stimulated sites with specific anatomical structures.
In this PhD project, we focused on: the anatomo-functional properties of the human hand representation in M1 (study 1); the oncological and functional efficiency of high-frequency mapping in tumours harbouring within M1 (study 2); the frontal premotor pathways involved in controlling fine hand movements (study 3).
Study 1, conducted on 17 patients who underwent an awake procedure, reported a possible subdivision, based on anatomo-functional analysis, of the human hand-knob in two sectors (a posterior one, close to the central sulcus, and an anterior one, close to the precentral sulcus) with different cortical excitability, different hand-muscle electromyographic (EMG) pattern when stimulations were delivered during the object manipulation task and, finally, with different local cortico-cortical connectivity. Overall data suggests that the two sectors may exert different roles in motor control.
Study 2 consisted of a retrospective analysis of 102 patients who underwent an asleep procedure for the removal of tumours harbouring with M1 and its descending fibres. The neurophysiological protocols adopted for the intraoperative brain mapping were correlated with the clinical condition, the tumour imaging features, the extent of the resection and the post-operative functional outcome. First, results indicated that M1 tumour removal is feasible and safe and the high frequency stimulation was revealed as the most efficient and versatile paradigm in guiding resection of M1, affording 85.3% complete resection and only 2% permanent morbidity. The study confirmed the possible subdivision of M1 in a rostral less excitable region and a caudal more excitable region reported in Study1 with its clinical impact: the rostral sector can be indeed considered a safe point of entry for surgery and thus for catheters.
Study 3 aimed at characterizing the effect of DES on the electrical activity (EMG) of hand movers during a dedicated object-manipulation task during subcortical stimulation of the frontal white matter anterior to M1 (precentral gyrus) and the anatomical evaluation of the stimulated sites by means of diffusion tractography, in 36 patients who underwent an awake surgery. Results indicated that stimulations of dorsal premotor connections with the spinal cord, dorsal striatum, local U-shaped connections and the superior longitudinal fasciculus I and II resulted in abrupt arrest of the hand, while more ventral stimulation, mainly targeting the third branch of the superior longitudinal fasciculus (SLF III) resulted in clumsy hand movements. Resection cavities analysis showed that transient post-operative upper-limb motor deficit occurred only disconnecting the supplementary motor area corticofugal fibres and the frontal U-shaped connections. Overall data suggests that DES on dorsal premotor white matter could interfere with areas involved in the very final stages of the motor program, while DES on ventral premotor white matter could halt the sensorimotor transformations necessary for correct hand shaping.
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Dhuldhoya, Aayesha Narayan. « Characterization of Temporal Interactions in the Auditory Nerve of Adult and Pediatric Cochlear Implant Users ». Diss., University of Iowa, 2013. https://ir.uiowa.edu/etd/4838.
Texte intégralRésumé :
Current cochlear implant systems use fast pulsatile stimulation to deliver the temporal modulations of speech and to, potentially, improve the neural representation of such modulations by restoring the independence of neural firing. The realization of these benefits may vary with other pulse rate-dependent temporal interactions that occur at the neural membrane, e.g., per(i)stimulatory adaptation and its post-stimulatory or forward masking effects. This study attempted to characterize adaptation and recovery of the electrically evoked compound action potential (ECAP) using probe pulses delivered within and following brief (100 ms) high-rate masker (1800 pps) pulse trains at various current levels in adults and children.
With this stimulus paradigm, the ECAP amplitude typically achieved a steady state during the course of pulse train stimulation. The ECAP amplitude at steady state was, on average, a similar proportion (50-70%) of the amplitude at onset for various stimulus levels and in both age groups. However, long-term adaptation effects, evidenced by the decrease in onset ECAP amplitude, were greater in adults particularly at lower levels in the ECAP dynamic range. Instances of alternation in ECAP amplitude were seen at stimulus levels that were higher in the ECAP dynamic range.
The forward masking effects of pulse train stimulation were quantified by the ECAP amplitude in response to a subsequent probe pulse normalized by the response to the same pulse presented alone. Pulse train forward masking increased with the level of the masker pulse train and decreased with the level of the probe stimulus. The recovery of the ECAP for probes that were lower in level than the masker pulse train was incomplete at 600 ms after masker offset, consistent with long-term cumulative effects observed in the response to the probe alone. Masker pulse trains that are lower in level than the probe pulse produced proportionally small decrements in the ECAP amplitude with complete recovery within 250 ms of pulse train offset particularly in adults. ECAP recovery of a probe preceded by a masker pulse train of equal level followed a monotonic or non-monotonic pattern consistent with a hypothesis of both adaptation and facilitation occurring with pulse train stimulation. The various patterns of recovery may attest to the occurrence of more than a single process in the same subset of nerve fibers or in different fibers. We hypothesize that the variations in the recovery patterns may be attributable to individual differences in the status of the auditory nerve and possibly, the variations in temporal interactions across the spatial domain at different stimulus levels.
Finally, the probe-evoked ECAP amplitude at steady state in children and briefly, e.g., 20 ms, after pulse train offset in both age groups could be predicted by the ECAP amplitude in response to the same probe pulse when preceded at a brief interval (1.2 or 2 ms) by a single masker pulse of the same level as the masker pulse train.
Further investigation may reveal if the observed differences in neural responsiveness to pulsatile stimulation, among individuals account for differences in psychophysical measures, including speech perception and whether there may be an "optimal" neural output that could be evoked by an individually "optimized" signal.
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Sousa, Marcus André Acioly de. « Critérios eletrofisiológicos de prognóstico da função facial baseados no pontencial evocado motor do nervo facial intraoperatório durante os diversos tempos cirúrgicos da cirurgia do schwannoma vestibular ». Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/5/5138/tde-31102011-172114/.
Texte intégralRésumé :
O potencial evocado motor facial (PEMF) tem-se mostrado um excelente método de monitorização do nervo facial, gerando resultados bastante confiáveis e reprodutíveis no que tange à predição da função facial pós-operatória. O critério eletrofisiológico mais utilizado até então para tanto tem sido a relação de amplitude do PEMF final-valor de base. Os objetivos deste trabalho foram avaliar as alterações intraoperatórias da amplitude e da complexidade do PEMF, correlacioná-las com o prognóstico facial no pós-operatório imediato e tardio e verificar se amplitude e complexidade constituem variáveis independentes de predição funcional. Os registros dos potenciais intraoperatórios dos músculos orbiculares do olho e da boca de 35 pacientes portadores de schwannoma vestibular (SV) foram coletados e analisados retrospectivamente de acordo com tempos cirúrgicos preestabelecidos: inicial, abertura da dura-máter, dissecação do tumor (TuDis), ressecção do tumor (TuRes) e final. No pós-operatório imediato, a função facial apresentou uma significativa correlação negativa com as relações de amplitude do PEMF durante a TuDis, a TuRes e ao final do procedimento nos músculos orbiculares do olho (p =0,003, 0,055 e 0,028, respectivamente) e da boca (p=0,002, 0,104 e 0,014, respectivamente). No último seguimento, entretanto, a correlação foi significativa apenas para o músculo orbicular da boca, durante a TuDis (p=0,005) e ao final do procedimento (p=0,102). As variações da complexidade dos potenciais alcançaram resultados mais significativos tanto no pós-operatório imediato, quanto no tardio, de forma que houve uma correlação negativa no músculo orbicular do olho apenas nas medidas finais (imediato, p=0;023; seguimento, p=0,116) e no músculo orbicular da boca durante a TuDis, a TuRes e a medida final (imediato, p=0,071, 0,000 e 0,001, respectivamente; seguimento, p=0,015, 0,001 e 0,01, respectivamente). As alterações intraoperatórias das relações de amplitude e de complexidade dos PEMFs parecem representar variáveis independentes, podendo ser utilizadas na predição da função facial pós-operatória durante cirurgias de ressecção de SV. Baseados nos resultados deste trabalho, a monitorização evento-valor de base é bastante útil, justificando mudanças imediatas da estratégia cirúrgica, com o intuito de reduzir as chances de uma lesão definitiva do nervo facial.Facial motor evoked potential (FMEP) amplitude ratio reduction at the end of the surgery has been identified as a good predictor for postoperative facial nerve outcome. We sought to investigate variations in FMEP amplitude and waveform morphology during vestibular schwannoma (VS) resection and to correlate these measures with postoperative facial function immediately after surgery and at the last follow-up. Besides we analyzed the relationship between quantitative parameters. Intraoperative orbicularis oculi and oris muscles FMEP data from 35 patients undergoing surgery for VS resection were collected, then analyzed by surgical stage: initial, dural opening, tumor dissection (TuDis), tumor resection (TuRes) and final. Immediately after surgery, postoperative facial function correlated significantly with the FMEP amplitude ratio during TuDis, TuRes and final in both the orbicularis oculi (p´s=0.003, 0.055 and 0.028, respectively) and oris muscles (p´s=0.002, 0.104 and 0.014, respectively). At the last follow-up, however, facial function correlated significantly with the FMEP amplitude ratio only during TuDis (p=0.005) and final (p=0.102) for the orbicularis oris muscle. At both time points, postoperative facial paresis correlated significantly with FMEP waveform deterioration in orbicularis oculi during final (immediate, p=0.023; follow-up, p=0.116) and in orbicularis oris during TuDis, TuRes and final (immediate, p´s=0.071, 0.000 and 0.001, respectively; follow-up, p´s=0.015, 0.001 and 0.01, respectively). FMEP amplitude ratio and waveform morphology during VS resection seem to represent independent quantitative parameters that can be used to predict postoperative facial function. Event-to-baseline FMEP monitoring is quite useful to dictate when intraoperative changes in surgical strategy are warranted to reduce chances of facial nerve injury.
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Botros, Andrew Computer Science & Engineering Faculty of Engineering UNSW. « The application of machine intelligence to cochlear implant fitting and the analysis of the auditory nerve response ». Awarded By:University of New South Wales. Computer Science & ; Engineering, 2010. http://handle.unsw.edu.au/1959.4/44707.
Texte intégralRésumé :
Effective cochlear implant fitting (or programming) is essential for providing good hearing outcomes, yet it is a subjective and error-prone task. The initial objective of this research was to automate the procedure using the auditory nerve electrically evoked compound action potential (the ECAP) and machine intelligence. The Nucleus?? cochlear implant measures the ECAP via its Neural Response Telemetry (NRT) system. AutoNRT, a commercial intelligent system that measures ECAP thresholds with the Nucleus Freedom implant, was firstly developed in this research. AutoNRT uses decision tree expert systems that automatically recognise ECAPs. The algorithm approaches threshold from lower stimulus levels, ensuring recipient safety during postoperative measurements. Clinical studies have demonstrated success on approximately 95% of electrodes, measured with the same efficacy as a human expert. NRT features other than ECAP threshold, such as the ECAP recovery function, could not be measured with similar success rates, precluding further automation and loudness prediction from data mining results. Despite this outcome, a better application of the ECAP threshold profile towards fitting was established. Since C-level profiles (the contour of maximum acceptable stimulus levels across the implant array) were observed to be flatter than T-level profiles (the contour of minimum audibility), a flattening of the ECAP threshold profile was adopted when applied as a fitting profile at higher stimulus levels. Clinical benefits of this profile scaling technique were demonstrated in a 42 subject study. Data mining results also provided an insight into the ECAP recovery function and refractoriness. It is argued that the ECAP recovery function is heavily influenced by the size of the recruited neural population, with evidence gathered from a computational model of the cat auditory nerve and NRT measurements with 21 human subjects. Slower ECAP recovery, at equal loudness, is a consequence of greater neural recruitment leading to lower mean spike probabilities. This view can explain the counterintuitive association between slower ECAP recovery and greater temporal responsiveness to increasing stimulation rate. This thesis presents the first attempt at achieving completely automated cochlear implant fitting via machine intelligence; a future generation implant, capable of high fidelity auditory system measurements, may realise the ultimate objective.
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Hocking, Christopher Anthony. « Brain electrical activity and automization / ». 1999. http://adt.lib.swin.edu.au/public/adt-VSWT20051021.110535.
Texte intégralRésumé :
Thesis (Masters by Research) - Swinburne University of Technology, Brain Sciences Institute, 1999."A thesis submitted of the requirement for the award of the degree Masters by Research, Brain Sciences Institute - 1999. Typescript. Includes bibliographical references (p. 141-164).
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Yuan, Wei-Chen, et 袁偉城. « Implementation of a Development System for Investigating the Relationship Between Acupoint Electrical Stimulation and Evoked Potentials ». Thesis, 2007. http://ndltd.ncl.edu.tw/handle/28637462201214932766.
Texte intégralRésumé :
碩士南台科技大學
電機工程系
95
According to the meridian theory and clinical evidences of Chinese medicine, acupoint stimulation utilizing such as manual acupuncture, electrical acupuncture, and massage to acupoints is well-known to have healthcare or therapeutic effects on some diseases. Next, in Western neuroscience medicine, evoked potentials induced through stimulation are also known to be used for checking the state of central nervous system of the human being. Except these evidences, many other studies have been verified that acupoint stimulation has related to the variety of evoked potentials of central nervous system. Based on the previous viewpoints, this study will develop a system with acupoint electrical stimulation and evoked potentials extraction functions. By this system, we can make such an acupuncture scientific research. The hardware of the system mainly includes two subsystems: (1) an acupuncture-like transcutaneous nerve electrical stimulator (AL-TENS): It can generate biphasic current stimulation waveform and can make five-section manual amplitude adjustment. It also can setup the duration and frequency directly via the developed graphical user interface; (2) an eight-channel EEG frond-end amplifier: It has a filter bandwidth of 0.1-50 Hz and an amplification rate of x13500. Moreover, the system GUI was developed by LabVIEW. It has the functions of real-time time / frequency domain analysis, time control of stimulation and data storage. The stored EEG data then were used for off-line evoked potentials extraction analysis via the EEGLAB software. Totally speaking, the acupoint stimulation and EEG measurement functions of the development system are basically satisfactory. After completing the system, we utilize it to stimulate some subject’s right hand Huge acupoints and then to examine their SEP. We found that the components of N20 and N80 are similar to the results obtained by a NeuroScan’s machine under the same testing condition. Next, we use a written LabVIEW-based pattern reversal stimulation program and select an Eye acupoint on the ears to stimulate in order to do the study of VEP variety. The results show that the N100, P135 and N160 components of VEP are also close to the test results obtained by the NeuroScan’s machine. Finally, using the Friedman variance analysis we find that the latency of VEP components has not apparent change before and after stimulation to the Eye acupoint of ears.
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Farrow, Maree. « Brain electrical activity topography in attention-deficit/hyperactivity disorder / ». 2003. http://adt.lib.swin.edu.au/public/adt-VSWT20050406.141958.
Texte intégralRésumé :
Thesis (PhD) - Swinburne University of Technology, Brain Sciences Institute, 2003.Thesis for Doctor of Philosophy, Brain Sciences Institute, Swinburne University of Technology - 2003. Typescript. Bibliography: p. 191-239.
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Kang, Yu-Tien, et 康玉典. « Comparative the effect of electroacupuncture and transcutaneous electrical nerve stimulation at bilateral Zusanli (St-36) acupointson median nerve-somatosensory evoked potentials ». Thesis, 2007. http://ndltd.ncl.edu.tw/handle/89577197802276428773.
Texte intégralRésumé :
碩士中國醫藥大學
針灸研究所碩士班
95
A number of the studies indicate that there is different physiological mechanism between electroacupuncture (EA) and transcutaneous electrical nerve stimulation (TENS). Therefore, the purpose of the present study was to investigate the effect of EA and TENS at bilateral Zusanli acupoints on median nerve-somatosensory evoked potentials (MN-SEPs) to compare the difference of physiological mechanism between EA and TENS. A total of 20 healthy adults’ volunteers were studied. We used 4 Hz electrical stimulation applied to median nerve of left wrist to obtain SEPs. The electrodes were placed on the skin of 7th cervical spine process to obtain spinal cord potentials N13, on the hand area of right sensory cortex scalp to obtain sensory cortex potentials N20-P25, and obtain the late component N30 and P44, respectively. 2 Hz EA and 2 Hz TENS applied to bilateral Zusanli and Shangjuxu acupoints, respectively. We observed the changes of latencies and amplitudes of N13, N20, P25, N30 and P44 components to compare the effect of EA and TENS on MN-SEPs. Three sessions of sham stimulation (no EA or TENS), 2 Hz EA and 2 Hz TENS were done in each subject. The interval between sessions was at least 7 days, and each session was divided into before acupuncture period, acupuncture period and post acupuncture. MN-SEPs recorded at least two times in each period. The results indicated that 2Hz EA could enhance the N20 and N30 amplitudes of MN-SEPs, but no similar change was found in the 2 Hz TENS and sham acupuncture. In conclusion, 2Hz EA can enhance the N20 and N30 amplitudes of MN-SEPs, but no similar change was found in the 2 Hz TENS and sham acupuncture, suggesting that there is different effect on cerebral cortex between 2 Hz EA and 2 Hz TENS; 2 Hz EA can not change the latency and amplitude of N13 component, but enhances the amplitude of N20 and N30, suggesting that main physiological mechanism of 2 Hz EA at Zusanli acupoints occur in the cerebral cortex.
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Huang, Hau-Shiou, et 黃浩修. « Patient-specific Models based on Evoked Compound Action Potential and Electrical Field Imaging ». Thesis, 2016. http://ndltd.ncl.edu.tw/handle/67049380601925852684.
Texte intégralRésumé :
碩士國立交通大學
生醫工程研究所
105
With physiological dimensions of the cochlear implant (CI) patient’s cochlea from computed tomography (CT), it is possible to build a more accurate patient-specific electro-neural model of CI patients based on clinical measurements. One of such methods is proposed in this thesis. An accurate patient specific electro-neural model could be used for fine tuning the electrical stimulation parameters or “maps” of a CI patient without needing many CI mapping sessions. This has enormous implication for CI pediatric applications due to obvious reason. The goal of this thesis is to evaluate the relative spiral ganglion cells (SGC) density of a human CI patient. The electric potential along the cochlea in a CI patient can be measured via electric field imaging (EFI). Also, there is a significant correlation between evoked compound action potential (ECAP) threshold and behavior threshold (T) level for a CI patient. ECAP measurement approach is an objective and faster way to obtain the relative T level of a CI patient. This again has important implication for pediatric CI mapping application since it does not require feedback from pediatric CI patients. Due to a large stimulating range, we propose to use the idea of using “apple-core”-ECAP paradigm which can limit the auditory nerves being stimulated to a narrower volume between neighboring two electrodes. Since the volume of auditory nerves activated and the distance between electrode and SGC are fixed, we can obtain the relative SGC density through comparing with every SGC signal at different electrodes.
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Lo, Tun-Shin, et 羅敦信. « Efficacy of electrically evoked auditory brainstem response and electrically evoked compound action potential in programming children with the Nucleus-24 Cochlear Implants ». Thesis, 2004. http://ndltd.ncl.edu.tw/handle/75360032289540431241.
Texte intégralRésumé :
碩士國立台北護理學院
聽語障礙科學研究所
92
Several reports have shown the benefit in speech perception of cochlear implants. Determination of behavioral threshold levels (T-levels) and comfort levels (C-levels) of the cochlear implant users is very important for their performance of auditory perception. Either electrically evoked compound action potential (ECAP) or electrically evoked auditory brainstem response (EABR) has been studied to help with optimizing individual’s map parameters of cochlear implant users, particularly young children, in whom accurate behavioral T-levels and C-levels to electrical stimulation are difficult to obtain. The purpose of this study was to evaluate the efficacy of EABR and ECAP in programming children with Nucleus-24 cochlear implants by comparing their thresholds with behavioral T-levels and C-levels. Seventeen subjects (7 males and 10 females) with Nucleus 24 cochlear implant participated in this study. All subjects have received implantation at least for one year. Behavioral T-level and C-level were measured through the speech processor. Their auditory behavioral responses were reliable and stable MAPs were established. ECAP thresholds were recorded with the NRT 3.0v software (Cochlear, Australia). EABR thresholds were measured with evoked potential technique (Bravo, Nicolet, USA). SPSS 10.0 for Windows (SPSS Inc., Chicago, USA) was used for analysis. Regression models and paired t-tests were used to analyze the correlations between ECAP threshold, EABR threshold, behavioral T-level and C-level. ECAP thresholds were measured successfully in 64% of active electrodes measured, whereas EABR thresholds were measured in 71%. Unsuccessful recording of ECAP and EABR was observed mostly in subjects either with severe malformations or calcification of inner ear. Both ECAP and EABR could not be measured in four cases. When the subjects with severe malformations or calcification of inner ear were excluded, the rate of successful measurement raised to 94.2 % for EABR and 84.6 % for ECAP, respectively. EABR thresholds were on average 6.17 programming units (current levels) higher than ECAP thresholds. The correlation between EABR and ECAP thresholds was moderate (r = 0.755) and significant (p < 0.01). Paired t-tests revealed no significant difference between EABR and ECAP statistically (p = 0.051). The correlation between behavioral T-levels and ECAP thresholds or EABR thresholds was fair (r = 0.409 and 0.304, respectively). The correlation between behavioral C-levels and ECAP thresholds was moderate (r = 0.61), whereas the correlation between behavioral C-levels and EABR thresholds were fair (r = 0.283). The correlation between behavioral maps and EABR thresholds or ECAP thresholds is not strong. However, EABR and ECAP can be used as ancillary tools in programming MAP T-levels and C-levels of young children. In general, the rate of successful recording of EABR was higher than that of ECAP. Because recording of ECAP is easier and less time consuming than EABR, ECAP may be the choice of objective measurement. EABR measurement may be preferable for individuals whose ECAP can not be recorded successfully. Because of the very low rate of successful recording in young children either with severe malformations or calcification of inner ear, measurement of EABR and ECAP may not play a role in programming them.
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Stamps, Kenyon. « A steady-state visually evoked potential based brain-computer interface system for control of electric wheelchairs ». 2012. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1001343.
Texte intégralRésumé :
M. Tech. Electrical EngineeringDetermines whether Hidden Markov models (HMM) can be used to classify steady state visual evoked electroencephalogram signals in a BCI system. This is for the purpose of aiding disabled people in driving a wheelchair.
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Liu, Chih-yu, et 劉致佑. « Development of a LabVIEW-based Integration Evaluation System for theCorrelation Study of Auricular Points Electrical/Magnetic Stimulationand Visual Evoked Potential ». Thesis, 2010. http://ndltd.ncl.edu.tw/handle/11175727271939916944.
Texte intégralRésumé :
碩士南台科技大學
電機工程系
98
In recent years, more and more people are suffering from eye diseases. Moreover, the age groups affected is gradually decreasing. Therefore, we cannot ignore the importance of eye care. Today it is known that Chinese auricular acupuncture can also improve this problem. However, the auricular acupuncture still needs technological and scientific approval. Therefore, this research developed an evaluation system that can use transcutaneous electrical nerve stimulation or magnetic stimulation to stimulate related auricular points to substitute for the current auricular acupuncture. In addition, it uses visual evoked potential for analysis, which can be used for scientific assessment and at the same time develop eye-related health devices. The research developed an evaluation system having an integrated hardware using low-power electric/magnetic stimulator, checkered screen visual stimulator with screen pattern reversal method, recording module and others. For the software portion, LabVIEW was used as the base for the control of the electrical /magnetic recording of the EEG stimulation and off-line analysis of evoked potential acquisition functions. The evaluation experimental method was made for those with moderate myopia and let them go through visual stimulation using screen pattern reversal method (1~3 Hz), acupoint electrical/magnetic stimulation (1~8 Hz) and other related parameters are set and remained unchanged. EEG electrodes were placed at Oz, O1 and O2 positions of the occipital zones. The preliminary results showed that two-sided auricular eye-acupoint stimulation can influence the change of the latencies of PR-VEP (p<0.005), and the activation function of visual nerve seems to be related to electrical/magnetic stimulation frequency. Results from the experimental data showed that electrical stimulation on the earlobe acupoint was more effective compared to magnetic stimulation. However, the coil was poorly designed therefore it cannot fully stimulate the acupoints. Finally, our results demonstrated a portable eye health care with electrical stimulation and magnetic stimulation.
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Smit, Jacoba Elizabeth. « Modelled response of the electrically stimulated human auditory nerve fibre ». Thesis, 2008. http://upetd.up.ac.za/thesis/available/etd-09182008-144232/.
Texte intégral
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(9356939), Jui-wei Tsai. « Digital Signal Processing Architecture Design for Closed-Loop Electrical Nerve Stimulation Systems ». Thesis, 2020.
Trouver le texte intégralRésumé :
Electrical nerve stimulation (ENS) is an emerging therapy for many neurological disorders. Compared with conventional one-way stimulations, closed-loop ENS approaches increase the stimulation efficacy and minimize patient's discomfort by constantly adjusting the stimulation parameters according to the feedback biomarkers from patients. Wireless neurostimulation devices capable of both stimulation and telemetry of recorded physiological signals are welcome for closed-loop ENS systems to improve the quality and reduce the costs of treatments, and real-time digital signal processing (DSP) engines processing and extracting features from recorded signals can reduce the data transmission rate and the resulting power consumption of wireless devices. Electrically-evoked compound action potential (ECAP) is an objective measure of nerve activity and has been used as the feedback biomarker in closed-loop ENS systems including neural response telemetry (NRT) systems and a newly proposed autonomous nerve control (ANC) platform. It's desirable to design a DSP engine for real-time processing of ECAP in closed-loop ENS systems.
This thesis focuses on developing the DSP architecture for real-time processing of ECAP, including stimulus artifact rejection (SAR), denoising, and extraction of nerve fiber responses as biomedical features, and its VLSI implementation for optimal hardware costs. The first part presents the DSP architecture for real-time SAR and denoising of ECAP in NRT systems. A bidirectional-filtered coherent averaging (BFCA) method is proposed, which enables the configurable linear-phase filter to be realized hardware efficiently for distortion-free filtering of ECAPs and can be easily combined with the alternating-polarity (AP) stimulation method for SAR. Design techniques including folded-IIR filter and division-free averaging are incorporated to reduce the computation cost. The second part presents the fiber-response extraction engine (FREE), a dedicated DSP engine for nerve activation control in the ANC platform. FREE employs the DSP architecture of the BFCA method combined with the AP stimulation, and the architecture of computationally efficient peak detection and classification algorithms for fiber response extraction from ECAP. FREE is mapped onto a custom-made and battery-powered wearable wireless device incorporating a low-power FPGA, a Bluetooth transceiver, a stimulation and recording analog front-end and a power-management unit. In comparison with previous software-based signal processing, FREE not only reduces the data rate of wireless devices but also improves the precision of fiber response classification in noisy environments, which contributes to the construction of high-accuracy nerve activation profile in the ANC platform. An application-specific integrated circuit (ASIC) version of FREE is implemented in 180-nm CMOS technology, with total chip area and core power consumption of 19.98 mm2 and 1.95 mW, respectively.
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Leško, Róbert. « Přínos jednotlivých intraoperačních elektrofyziologických metod u dětských epileptochirurgických pacientů ». Doctoral thesis, 2020. http://www.nusl.cz/ntk/nusl-435286.
Texte intégralRésumé :
Epilepsy, as the most common chronic neurological disease, affects a significant part of population (0.5-1%). Drug resistant epilepsy has a significant negative effect on the quality of life, psychiatric comorbidities, neurocognitive performance and the risk of SUDEP in children. Therefore, resective epilepsy surgery, the only curative treatment of this condition, can fundamentally reverse this unfavorable prognosis. An inevitable prerequisite for a good postoperative result is complete removal of the epileptogenic zone (EC) and preservation of eloquent areas (EC). At present, even with improving and new preoperative non-invasive methods, we don't have an exclusive diagnostic method for theirs delineation. The aim of this PhD study is to assess benefit of individual intraoperative electrophysiological (iEF) methods in pediatric patients with focal intractable epilepsy. The first study evaluates the importance of intraoperative electrocorticography (iECoG) in the localization of EZ. The study proved that iECoG serves as a reliable tool to guide surgical resection and may predict results of epilepsy surgery. iECoG-based modification of surgical plan is not associated with increased risk of significant complications. The second presented study analyzed the contribution of intraoperative electrical...