Dissertations / Theses: 'Somatosensory evoked potentials'

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Heath, P. D. "Cortical somatosensory evoked potentials in parkinsonism." Thesis, University of Oxford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233645.

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2

Katifi, Haider A. "Dermatomal somatosensory evoked potentials in lumbosacral radiculopathy." Thesis, University of Southampton, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278543.

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Hamilton-Bruce, Monica Anne. "Conventional and topographic electroencephalography and somatosensory evoked potential studies in ischaemic stroke." Adelaide, 1998. http://web4.library.adelaide.edu.au/theses/09PH/09phh222.pdf.

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Copies of author's previously published articles inserted. Bibliography: leaves I-LXIV. Assesses the diagnostic and prognostic value of early electroencephalography (EEG) and somatosensory evoked potential studies in cortical and non-cortical ischaemic stroke. Both conventional and topographic/quantitative studies were performed. A parallel study was carried out on healthy volunteers to provide an effective control. Equipment and quantitative EEG (qEEG) variability was also assessed.

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Leung, Nga-man Julia. "Affecting factors on reliability of intra-operative somatosensory evoked potentials monitoring /." View the Table of Contents & Abstract, 2007. http://sunzi.lib.hku.hk/hkuto/record/B38480608.

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5

Leung, Nga-man Julia, and 梁雅雯. "Affecting factors on reliability of intra-operative somatosensory evoked potentials monitoring." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B45011254.

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Liu, Hongtao, and 刘洪涛. "Fast signal extraction of somatosensory evoked potentials for intraoperative spinal cord monitoring." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B45697139.

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7

Li, Jiewei, and 李杰威. "Electroencephalograph feature extraction of somatosensory event related potential (ERP)." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/206587.

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Background: The event related potential (ERP) is an important electrophysiological response to an internal or external stimulus on human body. In some studies, the ERP-based brain computer interface (BCI) systems were created in visual or auditory modality. However, in these type of BCIs, either the eyes or ears of the users are occupied when they are making a choice. It is not convenient to communicate with others. Thus, a somatosensory ERP based BCI can be developed to overcome this issue. According to this, the analysis of somatosensory ERP features is necessary to evaluate if somatosensory ERP is eligible for BCIs as an input. Objective: 1. To study ERP features and design of P300 experiment. 2. To compare three types of P300 features elicited by three modalities. 3. To produce ERP response by electrical stimuli delivered to different position, and analyze ERP features. Methods: Two experiments were conducted. In experiment 1, three modalities, including visual, auditory and electrical modality, were used to produce P300 response. Experiment 2 only presented electrical stimuli. In experiment 1 two electrical stimuli were presented with different intensities at one location, whereas four electrical stimuli were showed at different location with the same intensity. The amplitude and latency were compared among three modalities, and the ERP topography of experiment 2 was also analyzed. Result and conclusion: Fourteen subjects’ data were analyzed in our study. The amplitude and latency of electrical P300 were similar to auditory ERP. But the ERP of visual modality had the largest amplitude and shortest latency. This result shows that electrical P300 can work as well as auditory P300 in BCIs, but not as good as visual P300. In experiment 2, the latency of electrical ERP occurred around 280 ms, and the amplitude and the topography showed that the largest amplitude was located around Cz electrode. This type of ERP in experiment 2 was considered as P3a, which also can be used in BCI systems.
published_or_final_version
Orthopaedics and Traumatology
Master
Master of Medical Sciences

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8

Whittle, Ian Roger. "Clinical applications of somatosensory evoked potentials in pediatric neurosurgery /." Title page, contents and summary only, 1985. http://web4.library.adelaide.edu.au/theses/09MD/09mdw627.pdf.

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Lam, Shing-chun Benny, and 林成俊. "Fast signal processing techniques for surface somatosensory evoked potentials measurement." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2003. http://hub.hku.hk/bib/B29246404.

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10

Potgieter, Brent Vivian. "The extraction of auditory and somatosensory evoked potentials for use in depth of anaesthesia monitoring." Thesis, University of Cape Town, 1995. http://hdl.handle.net/11427/25627.

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11

Hamilton-Bruce, Monica Anne. "Conventional and topographic electroencephalography and somatosensory evoked potential studies in ischaemic stroke / Monica Anne Hamilton-Bruce." Thesis, Adelaide, 1998. http://hdl.handle.net/2440/19249.

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Copies of author's previously published articles inserted.
Bibliography: leaves I-LXIV.
xxxviii, 239 [77], Lxiv leaves : ill. (chiefly col.) ; 30 cm.
Assesses the diagnostic and prognostic value of early electroencephalography (EEG) and somatosensory evoked potential studies in cortical and non-cortical ischaemic stroke. Both conventional and topographic/quantitative studies were performed. A parallel study was carried out on healthy volunteers to provide an effective control. Equipment and quantitative EEG (qEEG) variability was also assessed.
Thesis (Ph.D.)--University of Adelaide, Dept. of Medicine, 1998?

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12

Al-Shahry, Fayz. "Changes in the somatosensory evoked potentials during recovery from stroke." Thesis, University of Southampton, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241792.

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13

Gibson, Neil Alexander. "The assessment of asphyxiated term infants by somatosensory evoked potentials." Thesis, University of Edinburgh, 1995. http://hdl.handle.net/1842/21256.

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Forty healthy term infants had SEP measured from surface electrodes over the cervical cord and cortex after median nerve stimulation at the wrist. A wide normal range of response was encountered. The cervical response was fairly stable and consisted of up to three negative peaks with the largest amplitude peak at a mean of 10.2 mscec after the stimulus. The configuration was similar to that found in older children and adults. The cortical trace was found to vary markedly and consisted of a wave which was of increasing complexity with increasing postmenstrual age (PMA). The mean for the peak of the first negative wave (N1) being 30.0 msec. There was a negative correlation between increasing PMA and latency of N1. Subsequent study was made of 30 term infants over the course of their asphyxial encephalopathy. The cervical response was normal in all but one infant but three types of cortical SEP were measured in these infants: a normal response; a immature/delayed response or an absent response. In general, over time, the SEP went from abnormality towards normality. The more asphyxiated infants had the more abnormal SEP results. Ten of the infants died. The surviving infants were seen at a mean age of 12 months for a neurological examination and Griffiths developmental assessment. Thirteen were unequivocally normal, 4 had doubtful findings at follow-up and 3 had cerebral palsy. There was a good correlation between SEP results and outcome. All infants with normal SEP by 4 days of age were unequivocally normal at one year. All the others had abnormal SEP beyond four days. The results suggest that SEP is a useful objective test in the evaluation of term infants who have suffered perinatal asphyxia and has additive weight to encephalopathy grade in prognostic assessment.

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Mima, Tatsuya. "Somatosensory evoked potentials following proprioceptive stimulation of fingers in man." Kyoto University, 1997. http://hdl.handle.net/2433/202148.

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Asanuma, Kotaro. "Pre-movement gating of somatosensory evoked potentials after tibial nerve stimulation." Kyoto University, 2003. http://hdl.handle.net/2433/148736.

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16

Carvajal, Alexander. "Temporal and spatial dependency of high frequency wave collisions in rat somatosensory cortex." Online access for everyone, 2008. http://www.dissertations.wsu.edu/Thesis/Summer2008/A_Carvajal_062208.pdf.

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17

Carter, Bradley Graham. "The prediction of both short and long term outcomes follwing severe brain injury using somatosensory evoked potentials." Australasian Digital Theses Program, 2006. http://adt.lib.swin.edu.au/public/adt-VSWT20070130.153020/index.html.

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18

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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19

Campbell, J. A. "Observations on somatosensory evoked potentials recorded from within the human spinal cord." Thesis, University of Liverpool, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356249.

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20

Salian, Dilip. "En jämförelse av kortikal registrering mellan olika registreringspunkter vid Somatosensory evoked potentials." Thesis, Örebro universitet, Institutionen för hälsovetenskaper, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-84599.

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Bakgrund- Sensorisk evoked potentials (SEP) är en neurofysiologisk undersökningsmetod som används för att monitorera svarspotentialer från kroppens sensoriska nervsystem efter en sensorisk stimulering. Registreringen av sensorisk evoked potentials sker med små elektriska stimuleringar över en perifer sensorisk nerv och registreras från tre olika registreringskanaler som benämns N9 över plexus brachialis, N13 Erb’s punkt och N20 för det primär sensoriska cortexområdet. Metod- I denna studie bearbetas data från 20 registreringar för N20-kanalen. Med registreringen av den klinisk använda standardmontaget C3’-Fz som används vid Karolinska universitetssjukhuset, som jämförs mot nya registreringsmontagen C3’-CPz, CP3-Fz CP3-CPz. Stimulering skedde unilateralt över höger nervus medianus på handledsnivå. Syftet med studien var att ta reda på om det fanns någon statistisk signifikant skillnad mellan standardmontaget C3’-Fz mot de alternativa montagen med avseende på amplitud, duration och latenstid mellan två registreringsomgångar. Den statistiska analysen genomfördes med Wilcoxsons teckenranktest för differenserna av registreringsomgångarna i amplitud, duration och latenstid. Spearmans rangkorrelationstest användes för att visa sambandet mellan standardmontaget och de nya registreringsmontagen i amplitud. Resultat- Resultatet visade ingen statistisk signifikant skillnad mellan standardmontaget mot de alternativa montagen för differenserna av amplitud, duration och latenstid mellan de två registringsomgångarna. Korrelationen för amplituderna visade att montaget CP3-Fz hade en starkare grad av samband mot standardmontaget C3’-Fz jämfört med registreringsmontagen C3’-CPz och CP3-CPz. Slutsats- Slutsatsen av denna studie är att det inte fanns någon statistisk signifikant skillnad i differenserna för amplitud, duration och latenstiderna vid jämförelse av standardmontaget mot de nya alternativa montagen. Dock visade montage CP3-Fz på ett starkare samband mot den klinisk använda C3-Fz jämfört med resterande montage med avseende på amplituden.
Background-Sensory evoked potentials (SEP) are a neurophysiological examination method used to monitor electrical response potentials from the body’s sensory nervous system. The registration follows three recording channels throughout the sensory pathway as N9 over plexus brachialis, N13 over cervical vertebrae mentioned as Erb’ point and N20 represented for the primary somatosensory cortex area. Method- In this study data was collected from 20 registrations for N20 channel. Registration for this study measured the clinical used cortical registration montage at Karolinska university hospital C3’-Fz against new registration montages C3'-CPz, CP3-Fz and CP3-CPz, with stimulation on the right median nerve at wrist level unilateral. The purpose of the study was to see if there exists any significant difference between the standard montage C3’-Fz against the new alternative registration montages in regard to amplitude, duration and latency after two registration rounds. Wilcoxson’s singed rank test were used to compare the difference in amplitude, duration and latency between registration rounds. Spearman’s correlation test were used to show the correlation between the standard montage and the new registration montages in amplitude. Result-The result showed no statistical significant difference between the standard montage and the new alternative montages in amplitude, duration and latency for the two registration rounds. The correlation showed registration montage CP3-Fz with a greater correlation towards the standard montage C3’-Fz compared to registration montages C3’-CPz and CP3-CPz in amplitude. Conclusions- This study showed no significant difference in amplitude, duration and latency when it compared the standard montage C3’-Fz against the new alternative montages. The correlation in amplitude showed montage Cp3-Fz with a stronger correlation towards the clinical used registration montage compared to the other new alternative montages.

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21

Cebolla, Ana Maria. "The N30 component of the somatosensory evoked potentials: a new tool for EEG dynamic exploration of human brain in space." Doctoral thesis, Universite Libre de Bruxelles, 2010. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210020.

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Whether ongoing electroencephalogram (EEG) signal contributes to event related potential (ERP) generation is currently a matter of discussion for all sensory modalities. Resolving the controversy between additive and the oscillatory models has become crucial because evoked potentials are increasingly used in clinical practice as a physiological and neuropsychological index of brain areas or as a link with other functional approaches such as fMRI and the underlying network. The key issue is the search for a function underlying these mechanisms.

Somatosensory evoked potentials are robust indicators of the afferent information at cortical level. In particular, the frontal N30 component of SEP can serve as a reliable physiological index of the dopaminergic motor pathway (Insola et al. 1999, Pierantozzi et al. 1999). Its properties in sensory-motor gating and cognitive processes make its fine analysis particularly interesting. The physiological interpretation and the origin of the frontal N30 are still debated (Allison et al. 1991, Cheron et al. 1994, Karnovsky et al. 1997, Balzamo et al. 2004, Barba et al. 2005).

In this thesis we have investigated the mechanisms generating the N30 SEP component produced by electrical stimulation at median nerve at wrist, with reference to the current questioning of the additive and oscillatory models of the ERP (Sayers et al. 1974; Basar et al. 1980).

We have applied analysis of the spectral content of neuronal oscillatory activity recorded in electroencephalographic (EEG) in order to study of dynamic brain processing underlying the N30 component. Concretely for studying whether the occurrence of the N30 related input induce amplitude modulation and/or reorganization of EEG rhythms we have analyzed separately power perturbation and phase synchrony of single EEG oscillations trials by means of event-related spectral perturbation (ERSP) and intertrial coherence (ITC) measurements. In addition, in order to model brain localizations of phase synchrony and power enhancement and to compare them to model localization of the N30 SEP we used swLORETA, a distributive method of source analysis.

We have demonstrated that:

(1) Ongoing EEG signals contribute to the generation of the N30 component (Cheron et al. 2007).

(2) Dynamics of ongoing EEG signals underlie the specific behavior of the N30 during gating produced by movement execution (Cebolla et al. 2009).

(3) Localization of brain sources generating the N30 SEP component overlaps those generating beta-gamma ongoing oscillations at the same short latency (Cebolla et al. 2010).

Additionally the work developed during this thesis has served to develop a comprehensive, pragmatic paradigm to identify, evaluate and understand the somatosensory alterations in defined contexts, as illustrated by our recent work on perturbations and adaptations in astronauts over long term microgravity stay. We think that addressing this topic is essential in order to optimize and objectively evaluate adaptation to microgravity. We therefore proposed a detailed project to European Space Agency entitled “The frontal N30 somatosensory evoked potential for the study of sensory-motor and cognitive adaptations in weightlessness: NeuroSEP” (ILSRA 2009) in which we also proposed direct applications for quality of life aboard International Space Station, for the medical field and industry.
Doctorat en Sciences de la motricité
info:eu-repo/semantics/nonPublished

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22

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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Gaetz, William C. "Dynamics of transient and steady-state responses evoked by mechanical stimulation of the digits /." *McMaster only, 2001.

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Carter, Bradley Graham, and n/a. "The use of somatosensory evoked potentials in the prediction of outcome in brain injured children." Swinburne University of Technology, 2006. http://adt.lib.swin.edu.au./public/adt-VSWT20070130.153020.

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This thesis describes studies assessing the ability of somatosensory evoked potentials (SEPs) to predict outcome following severe brain injury by examining outcome and determining the predictive value of SEPs directly and in comparison to alternative tests in both patients and systematic reviews of the literature. Outcome was assessed using a functional and quality of life measure. It changed over time and was influenced by age, mechanism, timing and the type of outcome measure. When 5 year functional outcome was used, sensitivity and specificity for the initial SEPs were 63.2% and 93.3% with a positive predictive value of 92.3% for favourable outcome and 66.7%, 94.7% and 90.9% for unfavourable outcome prediction. SEPs predictive performance varied and was better in patients with 1 year outcomes, when outcome was measured with the quality of life tool and in patients suffering hypoxicischaemic encephalopathy. Importantly, only twelve false positives were identified in the systematic review of 55 studies from 903 patients with bilaterally absent SEPs. Eight of these false positives suffered focal lesions of the brain stem, large cerebral fluid collections or recent decompressive craniectomy which cause SEPs to be absent because of a mechanical disruption to the electrical signal. Comparisons between SEPs and other tests in the patient cohort and wider literature showed that SEPs were the best overall predictors of outcome but were outperformed by some clinical tests in specific areas. Specificity for unfavourable outcome prediction was better for ICP, CPP and the last pupillary response. In patients with any cause of brain injury, the combination of SEPs and Motor responses provided the best predictions for unfavourable outcome while for favourable outcome the best overall prediction and specificity were achieved with a combination of either SEPs or Motor responses and the best sensitivity with pupillary responses alone or a combination of either SEPs or Pupillary responses. The studies in this thesis provide a detailed evaluation of SEPs and showed that SEPs have a place in the prediction of outcome, alone or in combination with existing tests. Overall, they are superior to clinical tests and can be easily obtained at the bedside and in the presence of pharmacological paralysis and analgesia/sedation.

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Routhier, Nathalie. "Dipole source analysis of somatosensory evoked potentials in normal subjects and patients with disorders of cortical development." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0015/MQ37161.pdf.

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Routhier, Nathalie 1970. "Dipole source analysis of somatosensory evoked potentials in normal subjects and patients with disorders of cortical development." Thesis, McGill University, 1997. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=27902.

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The somatosensory representations of hands and feet were determined using spatio-temporal source analysis of median and posterior tibial nerve somatosensory evoked potentials (SEPs). In 10 control subjects, modeled generators mapped on MRI correlated well with the primary somatosensory cortex identified with strict radiological criteria. For median nerve stimulation, the main generator was located 3.5 mm from the central sulcus on average (after correction for eccentricity) and was perpendicular to it. For posterior tibial nerve stimulation, the main generator was slightly anterior to the central sulcus (average distance 6.6 mm) and pointed predominantly posteriorly and towards the longitudinal fissure. In 3 patients with central dysgenetic lesions, all with normal somatosensory functions, modeled generators were located outside the lesion, 2 of these generators being unequivocally displaced to adjacent normal cortex. The only exception was one patient with small amplitude SEPs, possibly explained by misaligned pyramidal cells inside the dysgenetic cortex.

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Farham, Craig Jeffrey. "Somatosensory processing by rat medial pontomedullary reticular formation neurones : responses to innocuous and noxious thermal and mechanical stimuli." Doctoral thesis, University of Cape Town, 1991. http://hdl.handle.net/11427/27146.

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This work examines somatosensory processing in "giant" neurones of the medial pontomedullary reticular formation (PMRF) in the rat, with particular emphasis on the response to cutaneous thermal stimuli. Thermal test stimuli were employed as these were deemed to be more precisely quantifiable than other forms of cutaneous stimulation. Activity was recorded from 235 PMRF neurones in 94 female Long Evans rats (270 to 320 g) anaesthetised with urethane (1,25g/kg, i.p.). Rectal temperature was closely controlled at 38 ± 0,5°C. Standard stereotactic and extracellular recording techniques were employed. PMRF giant neurones were identified by their stereotactic location, large, stable spike amplitudes of long duration, responses to cutaneous mechanical stimuli and receptive field properties, and spontaneous discharge characteristics. Ramp, step and sine wave cutaneous thermal stimuli (35-48 °C) were applied to the glabrous skin on the hindpaw by means of a computer-controlled Peltier device. The location of the units was confirmed by subsequent histology. One hundred and eleven neurones were located in nucleus reticularis pontis caudalis (NPC), and 124 in nucleus reticularis gigantocellularis (NGC). Mechanical stimulation excited 188 of 235 (80%) PMRF neurones (ON-m cells), and inhibited 40 (17%, OFF-m cells). Seven cells (3%) had mosaic receptive fields of excitation and inhibition (complex responses, CX-m). Twenty-eight percent of neurones were responsive to both weak and intense stimuli (mixed neurones). The remainder (72%) responded only to intense mechanical stimulation of the skin (high threshold neurones). The (excitatory or inhibitory) response of the mixed neurones to intense stimuli was generally greater than to mild stimuli, Receptive fields ranged in size from restricted (hindlimbs only) to very extensive (covering the entire body surface). Neurones with small receptive fields were almost exclusively of the high threshold type, and tended to be located in NGC, while mixed neurones tended to have larger receptive fields, and were located predominantly in NPC. Some portion of the hind limbs were represented in the receptive fields of all but one of the neurones studied, while the tail and/ or trunk were represented in 77%, and the forelimbs and face in 28% of receptive fields. Most of the cells responding to cutaneous mechanical stimulation had bilateral (usually symmetric) receptive fields. Spontaneous (background) activity occurred in the absence of any deliberate sensory stimulation in 72% of PMRF neurones. The frequency of spontaneous discharge rates ranged from O to 47 spikes/ s. The coefficient of variation of the spontaneous discharge rate of a given neurone was generally less than 20% (range O to 85%). Of the 235 identified mechanosensitive PMRF neurones, 203 (86%) also responded to cutaneous thermal stimulation (43-48 °C) of the ipsilateral hind paw. Eighty percent of these responded with increased discharge rates (ON-t cells), and 20% were inhibited (OFF-t cells). The polarities of response of individual PMRF neurones to mechanical and thermal stimuli, and to repeated ipsilateral and contralateral thermal stimuli, did not differ significantly. Following transient thermal stimulation, spontaneous discharge rates largely returned to pre-stimulus levels. The thresholds of response to slow ramp (0,15°C/s) and stepped (2°C/s) thermal stimuli occurred both in the innocuous and noxious temperature ranges (below and above 42°C, respectively). The threshold temperatures showed large variability to repeated identical thermal stimuli. Despite the poor reproducibility of the threshold responses, the distribution of thresholds to thermal ramp stimuli was consistently bimodal, with peaks occurring at 39 and 43°C. The bimodality persisted even when the ipsilateral and contralateral data were pooled. The modes of these threshold distributions conform to the maximum discharge ranges for warm and noxious cutaneous receptors. Thus, it is likely that thermal input to individual PMRF neurones is derived from both types of receptors. The responses of PMRF neurones to repeated thermal stimuli were stable and reproducible with respect to magnitude and time course. The average (static) and maximum (dynamic) responses to thermal stimuli were generally small: for example, the mean of the average responses to ramp stimuli was 5,9 spikes/s ± 11,0 SD, (range -28 to 40 spikes/s), and the mean of the maximum responses was 9,3 spikes/s ± 16,1 SD, (range -46 to 65 spikes/s). The absolute change in firing rate of individual PMRF neurones, and of the population, increased monotonically as a function of the intensity of stepped cutaneous thermal stimuli in the range 40 to 48 °C. However, their resolution, based on their average and maximum responses, was poor. Incorporating the post-stimulus responses into the comparisons between different stimulus intensities marginally increased the resolution of these neurones. Thus, while the majority of PMRF neurones are able to distinguish innocuous from noxious stimuli, few are capable of encoding stimulus intensity within the noxious range (above 43 °C). The majority (70%) of PMRF neurones responded to sustained thermal stimuli with a slow increase or decrease to a new static discharge rate which was maintained with little or no adaptation. Latency to onset of response to stepped thermal stimuli varied from 1 to 50 seconds, and the time to maximal response between 5-60 seconds. Many PMRF neurones also showed marked after-discharge for periods of up to 5 minutes after removal of the stimulus. The thermal receptive fields of over 90% of PMRF neurones were large, incorporating at least both hindlimbs. The extensive receptive field sizes of individual PMRF neurones provides evidence against them having a role in stimulus location. The large number of PMRF neurones showing multimodal convergence, their small magnitude responses, their slow response times, and their large receptive fields strongly suggest that these neurones are not participating in classical sensory discrimination. Rather, they may function as stimulus detectors or alternatively play a role in associative processes.

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Silva, Daniel de Souza e. "Estudos das lesões de vias medulares através dos potenciais evocados somatossensitivos (PESS) e motores (PEM) em pacientes com mucopolissacaridoses (MPS)." Instituto Fernandes Figueira, 2013. https://www.arca.fiocruz.br/handle/icict/8263.

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Fundação Oswaldo Cruz. Instituto Fernandes Figueira. Departamento de Ensino. Programa de Pós-Graduação em Saúde da Criança e da Mulher. Rio de Janeiro, RJ, Brasil.
As mucopolisacaridoses (MPS) são doenças geneticamente determinadas, causadas pela deficiência de enzimas lisossômicas, o que leva ao acúmulo de glicosaminoglicanos (GAGs) universalmente. As mielopatias cervicais ao nível da junção craniocervical são uma complicação frequente, grave e multifatorial das MPS. Este trabalho teve como principal objetivo o estudo das vias sensitivas e motoras centrais (cordão posterior e trato córtico-espinhal) em topografia medular cervical nos pacientes com mucopolissacaridoses (MPS), utilizando os potenciais evocados somatossensitivos e motores. Como objetivos específicos, a avaliação dos pacientes com MPS em fases distintas da doença, a demonstração da existência de comprometimento da condução nervosa nos trajetos das vias medulares na topografia já mencionada e o destaque do papel dos testes neurofisiológicos (funcionais) no diagnóstico, acompanhamento e na tomada de decisões terapêuticas nos pacientes com MPS. Foi realizado um estudo transversal, de uma série de casos, tendo como metodologia a revisão de prontuários, no Instituto Nacional de Saúde da Mulher, da Criança e do Adolescente Fernandes Figueira. Foram incluídos os pacientes com o diagnóstico de MPS, sem restrições quanto à idade, aos subtipos da doença ou ao fato de estarem ou não sob tratamento específico e excluídos aqueles pacientes com lesões graves do sistema nervoso central que impedissem a realização dos testes propostos. Os dados colhidos referiram-se à idade dos pacientes, o tipo de MPS, os achados do exame neurológico, os resultados dos estudos de imagem (ressonância magnética) da coluna cervical e os parâmetros neurofisiológicos encontrados nos potenciais evocados somatossensitivos (PESS) e motores (PEM), que incluiram as latências das ondas (N9, N13 e N20 nos PESS de membros superiores e N21 e P37 nos PESS de membros inferiores), os tempos de condução central (N20 – N13 e P37 – N21) e o tempo de condução motora central (nos PEM de membros superiores e inferiores). Foram analisados resultados de cinquenta e oito exames de potenciais evocados somatossensitivos e motores, realizados em vinte e oito pacientes com MPS. Todos os exames foram anormais, com alterações mais graves nos exames de PEM.
Mucopolysaccharidosis (MPS) are inherited metabolic diseases caused by deficiency of lysosomal enzymes leading to progressive accumulation of glycosaminoglycans (GAGs) in nearly all cell types, tissues and organs. Cervical myelopathy at the cranio-cervical junction is a frequent, severe and multifactorial complication of MPS. The first objective of the present study is the evaluation os the function of central neural pathways (brain stem and spinal cord posterior columns and corticospinal tract in patients with MPS using somatosensory evoked potentials (SEP) and motor evoked potentials (MEP). The secondary objectives are the evaluation of the patients in different periods of disease, the diagnostic of the lesions in cervical spinal cord and the remark of the role of these neurophysiological tests in diagnostic, follow-up and therapeutic decisions. This cross-sectional study included all patients with MPS of Instituto Nacional de Saúde da Mulher, da Criança e do Adolescente Fernandes Figueira, despite age, type of disease, enzyme replacement therapy or not, except the patients with severe central nervous system lesions in whom the neurophysiological evaluation became impossible. Data included the age of patients, type of disease, the findings in neurological examination, magnetic resonance imaging of cervical spinal cord and the neurophysiological parameters [the latencies of N9, N13 and N20 waveforms, central conduction time (upper limbs SEP), the latencies of N21 and P37 waveforms, central conduction time (lower limbs SEP), central motor conduction time (upper and lower limbs MEP)].Twenty-eight patients were enrolled and fifty-eigth tests (SEP and MEP, upper and lower limbs) were performed in these patients. All tests were abnormal with most severe functional impairment in MEP tests.

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Albanese, Marie-Claire. "FMRI evidence of memory representations of somatosensory stimuli in the human brain." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=102949.

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Distinct brain regions process innocuous vibration and cutaneous heat pain. The role of these areas in the perception of pain is still a matter of debate; and the role of these areas in the mediation of memory of somatosensory stimuli is uncertain and has not been studied with brain imaging in healthy human volunteers. All experiments described here, involved an experimental design, which included a delayed-discrimination paradigm and functional magnetic resonance imaging (fMRI). In manuscript #1, we aimed at unraveling the cerebral correlates of attention and spatial localization of innocuous vibrotactile stimuli applied to the right volar surface of the forearm. In this study, we report that increased degrees of attention to the vibrotactile stimuli were associated with heightened levels of activation in several brain areas. In manuscript #2, we investigated the short-term memory for sensory aspects (intensity and location) of cutaneous heat pain delivered to two areas (thenar and hypothenar eminences) of the palm of the right hand. In this experiment, the memory and control trials were presented in blocks, whereby the subjects could predict what trials were going to follow. This study revealed that the presentation of painful stimuli evoked activation in different brain regions than those activated during the online maintenance (interstimulus interval or ISI) of the intensity and spatial features of those stimuli; a process, which I will refer to short-term memory. In manuscript #3, we investigated again short-term memory for sensory aspects of heat pain (as in manuscript #2), but in this case, the memory and control trials were presented in a randomized order. In this study, we found that the perception and short-term memory of pain were processed by a comparable network of areas. The predictability of the memory and control trials may have contributed to these findings.
La vibration inoffensive ainsi que la chaleur douloureuse cutanée sont traitées pardifférentes régions du cerveau. Le rôle de ces régions dans la perception de la douleurest controversé; et le rôle de ces régions dans la mémoire des stimuli somatosensorielsest incertain et n'a jamais encore été étudié en imagerie cérébrale chez des sujetshumains sains. Le design expérimental de toutes les études décrites ici comprenait unparadigme de 'delayed-discrimination' et l'imagerie par résonance magnétiquefonctionnelle (IRMf). L'étude #1 visait à élucider les corrélats cérébraux de l'attention etde la localisation spatiale des stimuli vibrotactiles inoffensifs présentés à la faceantérieure de l'avant-bras droit. Dans cette étude, nous avons trouvé que des degrésélevés d'attention portée aux stimuli vibrotactiles étaient associés à des niveaux accrusd'activation dans plusieurs zones du cerveau. Dans l'étude #2, nous avons enquêté surla mémoire à court-terme des caractéristiques sensorielles (intensité et emplacement)de la chaleur douloureuse cutanée présentée à deux endroits (éminences thénar ethypothénar) de la paume de la main droite. Dans cette étude, les essais mémoire etcontrôle étaient présentés en bloc, ou de sorte que les participants pouvaient prévoir dequel type serait le prochain essai. Cette étude a révélé que la présentation des stimulidouloureux a évoqué une activation de différentes régions cérébrales que celles quiétaient activées lors de la rétention de l'intensité et de l'emplacement des stimulationsdurant l'intervalle inter-stimuli (liS); un processus que je qualifierai de mémoire à courtterme.Dans l'étude #3, nous avons également enquêté sur la 'mémoire à court-termedes aspects sensoriels de la chaleur douloureuse (tout comme dans l'étude #2), maisdans ce cas, les essais mémoire et contrôle étaient présentés de façon aléatoire. Danscette étude, nous avons trouvé que la perception de la douleur ainsi que la mémoire àcourt-terme de la douleur étaient traitées par un réseau de régions semblable. Laprévisibilité des essais mémoire et contrôle peut avoir contribué à ce résultat.

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Oyama, Alberto Mitsuo. "Eliminação de artefatos de estímulo em potenciais evocados somatossensitivos." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/3/3142/tde-19012011-094249/.

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Os potenciais evocados têm uma consagrada utilização em clínica. Sua obtenção é dificultada pela presença de outros sinais biológicos, de artefatos de movimento, de ruído eletrônico, de interferência da rede elétrica e de artefatos de estímulo. A média síncrona ou promediação é um método que elimina os sinais que não estejam sincronizados com a estimulação, incluindo os outros sinais biológicos, os artefatos de movimento, o ruído e a interferência. No entanto, esse método não consegue eliminar os artefatos de estímulo. Outros métodos devem ser usados para essa tarefa. Para esses métodos, a eliminação do artefato de estímulo é bem sucedida quando o artefato não se sobrepõe ao potencial evocado. Porém, para uma captação próxima ao local de estimulação, a sobreposição ocorre e dificulta a eliminação do artefato de estímulo. O objetivo deste trabalho foi o de estudar a variação da amplitude e latência do pico do potencial evocado e sua influência nas estimativas da amplitude, da latência e do erro quadrático médio. Para potenciais evocados em que houve sobreposição com o artefato, o erro médio quadrático sempre foi reduzido com a remoção do artefato de estímulo. O erro de medição da latência foi reduzido a praticamente zero, independentemente da amplitude do potencial evocado. Por outro lado, o método inseriu erro na medição da amplitude de potenciais evocados grandes. Por isso, nesse caso específico de atraso pequeno e amplitude grande, a medição da amplitude deve ser feita diretamente no sinal antes da remoção do artefato de estímulo. Comparando a ocorrência de sobreposição com os locais de captação do potencial evocado, pode-se afirmar que, para o modelo de artefato de estímulo usado neste trabalho, a necessidade de se aplicar o procedimento de remoção de artefato se restringiu aos potenciais evocados captados no cotovelo, para estimulação do nervo mediano tanto no punho quanto na mão.
Evoked potentials have been used in clinics. Their measurement is hindered by the presence of other biological signals, movement artifacts, electronic noise, power-line interference, and stimulus artifacts. Synchronous averaging is a method that eliminates the signals that are not synchronized with the stimulation, including other biological signals, movement artifacts, noise and interference. However, this method fails to eliminate stimulus artifacts. Other methods must be used in this task. Using these methods, one can obtain success in the stimulus artifact elimination, whenever the artifact does not superimpose with the evoked potential. Nevertheless, for a measurement close to the stimulation site, the superimposition is a fact that hinders the elimination of the stimulus artifact. The objective of this Masters thesis was to study the variation of the amplitude and latency of an evoked potential and verify their influence on the amplitude and latency estimates, as well as on the mean square error. For evoked potentials in which there was superposition, the mean square error was always reduced by the removal of the stimulus artifact. Latency measurement errors were reduced to zero, regardless of the evoked potential amplitude. However, this method inserted amplitude measurement errors for large evoked potentials. So, in the case of short delays and large amplitudes, amplitude measurements should be performed directly on the signal, before stimulus artifact removal. By comparing the presence of superposition with the evoked potential recording sites, one may state that, for the stimulus artifact model used in this work, the need to apply the artifact removal procedure was restricted to the evoked potentials recorded on the elbow, for median nerve stimulation both on wrist and hand.

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Detloff, Megan Ryan. "Supraspinal Sensory Perception after Spinal Cord Injury and the Modulatory Factors Associated with Below-Level Allodynia." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1238174873.

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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 cruciale
The 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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Bradley, Claire. "The first steps of cortical somatosensory and nociceptive processing in humans : anatomical generators, functional plasticity, contribution to sensory memory and modulation by cortical stimulation." Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10213.

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Les sensations en provenance de notre corps se combinent pour donner lieu à des perceptions extrêmement variées, pouvant aller de la brûlure douloureuse au toucher agréable. Ces deux types d'informations dites nociceptives et non nociceptive sont traitées au sein du système nerveux somatosensoriel. Dans ce travail de thèse, nous avons modélisé et caractérisé l'activité électrique du cortex operculo-insulaire au sein des réseaux somatosensoriels non-douloureux et nociceptif, grâce à des enregistrements non-invasifs chez l'Homme. La validité du modèle en réponse à un stimulus nociceptif a été évaluée par comparaison avec des enregistrements intra-corticaux réalisés chez des patients épileptiques. Nous avons ensuite utilisé ce modèle pour déterminer si la stimulation corticale non invasive classiquement utilisée pour soulager les douleurs neuropathiques (stimulation magnétique du cortex moteur) permettait de modifier les réponses nociceptives chez des participants sains. Nous avons montré que cette intervention n'est pas plus efficace qu'une stimulation factice (placebo) sur le plan du blocage nociceptif. Finalement, nous avons tenté de stimuler directement le cortex operculo-insulaire, par trois méthodes différentes : par stimulation électrique locale, intracrânienne et par stimulations non-invasives magnétique (rTMS) et électrique (tDCS). Dans l'ensemble, les travaux présentés ici montrent comment une approche non-invasive chez l'Homme permet de caractériser et de moduler l'activité du cortex operculo-insulaire, qui pourrait être une cible intéressante pour le traitement des douleurs réfractaires
The somatosensory system participates in both non-nociceptive and nociceptive information Processing. In this thesis work, we model and characterize the electrical activity of the operculo-insular cortex within non-painful and nociceptive networks, using non-invasive electrophysiological recordings in humans. Validity of the modeled response to a nociceptive stimulus was evaluated by comparing it to intra-cranial recordings in epileptic patients, revealing excellent concordance. We went on to use this model to determine whether a technique of non-invasive cortical stimulation currently used to relieve neuropathic pain (motor cortex magnetic stimulation) was able to modulate acute nociceptive processing in healthy participants. We show that this intervention is not more efficacious than placebo stimulation in blocking nociception. This raises questions regarding the mechanisms of action of this technique in patients, which might implicate a modulation of pain perception at a higher level of processing. Finally, we attempted to stimulate the operculo-insular cortex directly, using three different methods. Low-frequency intra-cortical stimulation in epileptic, transcranial magnetic stimulation (TMS) of the same region in healthy participants and multipolar transcranial electrical stimulation (tDCS).Altogether, the studies presented here show how a non-invasive approach in humans allows characterising and modulating the activity of the operculo-insular cortex. While this region might be an interesting target for future treatment of drug-resistant pain, its stimulation in patients would require further investigation of parameters and procedures

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Vedrana, Karan. "Korelacija nalaza intraoperativnog neurofiziološkog monitoringa sa kliničkim nalazom kod prednje mikrodiskektomije vratnog segmenta kičme." Phd thesis, Univerzitet u Novom Sadu, Medicinski fakultet u Novom Sadu, 2019. https://www.cris.uns.ac.rs/record.jsf?recordId=110026&source=NDLTD&language=en.

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Degenerativne bolesti kičme nastaju kao posledica promena na dinamičkim segmentima kičmenog stuba. Klinički ove promene se mogu manifestovati u vidu radikulopatije, mijelopatije i radikulomijelopatije. Najčešće primenjivana metoda operativnog lečenja kod ovih pacijenata je prednja cervikalna diskektomija sa fuzijom koja omogućava adekvatnu anatomsku i funkcionalnu restituciju degenerativno promenjene cervikalne kičme. Imajući u vidu da su već kompromitovane nervne strukture u riziku od dodatnih oštećenja u različitim fazama operativnog zahvata primena intraoperativnog neurofiziološkog monitoringa je dobila svoje mesto i u hirurškim tretmanima degenerativnih oboljenja kičme. Svrha primene neuromonitoringa je da obezbedi povratnu informaciju hirurgu o promenama u funkciji nervnih struktura pre nego što dođe do ireverzibilnih oštećenja. Na ovaj način moguće je prevenirati nastanak novog ili pogoršanje postojećeg deficita. Takođe intraoperativni nalazi neurofizioloških parametara mogu da ukažu na težinu postojećeg oboljenja i da budu prediktori ishoda lečenja. Ciljevi ove doktorske disertacije bili su utvrđivanje faza operativnog zahvata u kojima najčešće dolazi do promena u neurofiziološkim parametrima, kao i postojanje korelacije nalaza intraoperativnog neurofiziološkog monitoringa sa preoperativnim kliničkim nalazom pacijenta kao i rezultatima procene ishoda nakon prednje cervikalne diskektomije se fuzijom. Ova studija je obuhvatila 30 pacijenata kod kojih je indikovano operativno lečenje degenerativnih promena u vratnom segmentu kičmenog stuba prednjom mikrodiskektomijom sa fuzijom. Preoperativno je izvođen klinički pregled pacijenata i korišteni su Numerička skala bola i Upitnik za pacijente sa bolom u vratnoj kičmi, koji su takođe popunjavani na otpustu i mesec dana nakon operacije. U toku hirurške procedure upotrebom intraoperativnog neurofiziološkog monitoringa registrovani su somatosenzorni (SSEP) i motorni evocirani potencijali (MEP), kao i spontana elektromiografija. Kod svih SSEP došlo je do statistički značajnog povećanja amplitude (p<0,05), dok je kod desnog n. medianusa zabeleženo i statistički značajno skraćenje latence (p<0,05). Značajne promene se beleže između početka i kraja operativnog zahvata, kao i u fazi uklanjanja intervertebralnog diska kada dolazi do dekompresije. U vrednostima pražne struje potrebne za dobijanje MEP nije bilo statistički značajnih promena izuzev kod m. triceps brachii obostrano. Kod pacijenata sa radikulopatijom vrednost pražne struje za dobijanje mišićnog odgovora je statistčki značajno niža u odnosu na pacijente sa mijelopatijom (p<0,05). SSEP koreliraju sa poremećajem senzibiliteta, refleksnim odgovorom i bolom. MEP koreliraju takođe sa refleksnim odgovorom, dok negativna korelacija sa manuelnim mišićnim testom pokazuje da klinički očuvana gruba mišićna snaga ne mora biti pokazatelj pravog stanja motornog sistema. Preoperativne vrednosti NDI su se statistički značajno smanjile mesec dana nakon operacije (p<0,05). U vrednostima bola postoji statistčki značajna razlika između svih merenje (p<0,008), izuzev između bola na otpustu i mesec dana nakon operacije (p>0,008). Latenca desnog n.medianusa pokazuje negativnu, a amplituda pozitivnu korelaciju sa vrednostima bola mesec dana postoperativno (p<0,05). Povećanje amplitude i skraćenje latence SSEP ukazuje na značajan stepen dekompresije. Stabilnost MEP ukazuje na intraoperativnu očuvanost motornih puteva i da nije došlo do novog motornog deficita niti produbljivanja postojećeg. SSEP i MEP koreliraju sa kliničkim nalazom, dok su vrednosti bola i NDI statistički značajno manje nakon operacije. Ovi rezultati ukazuju da klinički nalaz pacijenta korelira sa neurofiziološkim nalazom, kao i da introperativne promene neurofizioloških parametara mogu biti prediktivni faktor ishoda operativnog lečenja.
Degenerative spinal diseases are consequence of spondylotic changes on dynamic segments of spinal column. These changes can result in different clinical appearances such as radiculopathy, myelopathy and radiculomyelopathy. The most common surgical procedure used in treatment of this group of patients is anterior cervical discectomy and fusion (ACDF) which can provide adequate anatomical and functional restitution of degenerative cervical spine. Considering the fact that already compromised neural structure can be additionally damaged in different stages of surgical procedure, use of intraoperative neurophysiological monitoring (IONM) has role in surgical treatment of degenerative spinal diseases. The aim of use of IONM is to provide real time feedback for surgeon regarding changes in function of neural structures before irreversible damage occurs. This is the way to prevent new neurological deficit from occurring or to prevent worsening of preexisting deficit. Results of intraoperative monitoring can additionally emphasize severity of disease and help in outcome assessment. The aim of this doctoral thesis was to determine phases of surgical procedure in which changes in neurophysiological parameters occurs most commonly. Another aim was to determine correlation between findings of intraoperative neurophysiological monitoring and clinical assessment and outcome prediction in patients treated with anterior cervical discectomy with fusion. Thirty patients who met inclusion criteria were enrolled in this study. All of them were treated surgically due to degenerative changes of cervical spine and ACDF were performed in all cases. Patients were thoroughly examined before surgery. Detailed neurological examination were performed together with Numeric pain rating scale (NPRS) and Neck Disability index (NDI) questionnaire. NPRS and NDI were applied on discharge from the hospital and one month after surgery. During surgery we registered somatosensory evoked potentials (SSEP), motor evoked potentials (MEP) and spontaneous elektromiography. In all SSEP there were statistically significant increase in amplitude (p<0.05), while in the case of right n. medianus statistically significant shortening of the latency (p<0.05) was recorded. Significant changes are recorded between beginning and the end of the surgical procedure, as well as in the phase of removing of the intervertebral disc when decompression occurs. In the threshold intensity needed to elicit the MEP there were no statistically significant changes except for m. triceps brachii bilaterally. In patients with radiculopathy, the value of the stimulus intensity needed for obtaining muscular response was statistically significantly lower in comparison with patients with myelopathy (p<0.05). SSEP showed the best correlation with sensory disorder, tendon reflexes and pain. MEPs also correlate with tendon reflexes, while a negative correlation with a manual muscle strength testing results shows that clinically preserved muscle strength does not have to be reliable indicator of the motor system condition. Preoperative NDI values were statistically significantly reduced a month after surgery (p<0.05). In pain values there is a statistically significant difference between all measurements (p<0.008), except between pain on release and a month after surgery (p>0.008). The right n.medianus latency shows a negative, and the amplitude shows positive correlation with pain values one month postoperatively (p<0.05). Increasing amplitude and shortening latency of the SSEP indicates a significant degree of decompression. The stability of the MEP indicates the intraoperative preservation of motor pathways and absence of both new motor deficiency or worsening of the existing one. SSEP and MEP correlate with clinical findings, while pain and NDI values are statistically significantly less after surgery. These results indicate that clinical findings in the patients correlate with the neurophysiological findings. Results also points out that the intraoperative changes in neurophysiological parameters can be a predictive factor for the outcome of surgical treatment.

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Shimazu, Hideki. "Pre-movement gating of shortlatency somatosensory evoked potentialsに関する研究-短潜時体性感覚誘発電位の運動準備状態での変化." Kyoto University, 2000. http://hdl.handle.net/2433/151423.

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Ying, Zhong. "Motor and somatosensory evoked potential in coma /." Bern, 1991. http://www.ub.unibe.ch/content/bibliotheken_sammlungen/sondersammlungen/dissen_bestellformular/index_ger.html.

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Parsa, Vijay. "Interference reduction techniques for somatosensory evoked potential enhancement." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq23871.pdf.

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Saradjian, Anahid. "Mise en évidence d'une facilitation proprioceptive corticale pendant la planificationd'un pas exécuté ou imaginé. : Etude en microgravité et normogravité." Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM4061.

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Les informations sensorielles peuvent être atténuées de la périphérie jusqu'au cortex durant le mouvement. Notre hypothèse est que l'information somatosensorielle serait facilitée durant la planification du pas où il serait inopportun de supprimer ces informations cruciales. Nous avons enregistré les potentiels somatosensoriels (SEPs) évoqués par vibration bilatérale des muscles des chevilles afin de stimuler la proprioception.Les résultats montrent que la composante évoquée corticale précoce restait inchangée mais une composante tardive négative était significativement augmentée durant la planification du pas.Pour tester si cette facilitation proprioceptive était due aux contraintes d'équilibre, la même expérience fut effectuée en microgravité où cette facilitation disparut, malgré la restauration d'un cadre de référence spatial.Cette facilitation tardive survint pendant l'imagerie motrice kinesthésique d'un pas planifié, démontrant que l'imagerie mentale intègrerait les contraintes d'équilibre et posturales requises pour la tâche, ceci étant confirmé par la disparition de cette facilitation lors de la planification du pas imaginé en microgravité.Ceci démontre au niveau neurophysiologique, une modulation de la transmission des afférences sensorielles selon leur pertinence pour planifier un mouvement. Cette facilitation résulterait de mécanismes prédictifs reliés à l'importance de contrôler l'équilibre du corps avant l'initiation du pas, car ce processus survint durant la planification d'un pas exécuté ou imaginé. Il serait basé sur un modèle interne de l'action impliquant des lois physiques du mouvement (1-g modèle) car cette facilitation fut supprimée en microgravité
Sensory inputs can be attenuated from the periphery to the cortex during voluntary movements. Our hypothesis is that the somatosensory information could be facilitated during the planning of a step. It would appear dysfunctional to suppress somatosensory information, which is considered to be of the utmost importance for gait planning. We recorded somatosensory potentials (SEPs) evoked by bilateral ankle vibration to stimulate proprioception. Results showed that cortical early evoked component remained unchanged but a negative late component was significantly increased during step planning. To determine whether this facilitation of proprioceptive inputs was related to gravitational equilibrium constraints, we performed the same experiment in microgravity. In the absence of equilibrium constraints, both components did not significantly differ between the static and stepping conditions, despite the restoration of a body in space reference frame.This late facilitation occurred during kinesthetic motor imagery of a planned step, suggesting that mental imagery would integrate postura and balance constraints required for the task, as it was confirmed byt the lack of this facilitation during the planning of an imagined step in microgravity.These observations provide neurophysiological evidence that the brain exerts a dynamic control over the transmission of the afferent signal according to their current relevance during movement preparation.These processes should be based on internal model of action involving the physical laws of motion (1g-model) as this sensory facilitation was suppressed in microgravity when planning motor imagery

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Vedala, Krishnatej. "A Novel Signal Processing Method for Intraoperative Neurophysiological Monitoring in Spinal Surgeries." FIU Digital Commons, 2013. http://digitalcommons.fiu.edu/etd/1038.

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Intraoperative neurophysiologic monitoring is an integral part of spinal surgeries and involves the recording of somatosensory evoked potentials (SSEP). However, clinical application of IONM still requires anywhere between 200 to 2000 trials to obtain an SSEP signal, which is excessive and introduces a significant delay during surgery to detect a possible neurological damage. The aim of this study is to develop a means to obtain the SSEP using a much less, twelve number of recordings. The preliminary step involved was to distinguish the SSEP with the ongoing brain activity. We first establish that the brain activity is indeed quasi-stationary whereas an SSEP is expected to be identical every time a trial is recorded. An algorithm was developed using Chebychev time windowing for preconditioning of SSEP trials to retain the morphological characteristics of somatosensory evoked potentials (SSEP). This preconditioning was followed by the application of a principal component analysis (PCA)-based algorithm utilizing quasi-stationarity of EEG on 12 preconditioned trials. A unique Walsh transform operation was then used to identify the position of the SSEP event. An alarm is raised when there is a 10% time in latency deviation and/or 50% peak-to-peak amplitude deviation, as per the clinical requirements. The algorithm shows consistency in the results in monitoring SSEP in up to 6-hour surgical procedures even under this significantly reduced number of trials. In this study, the analysis was performed on the data recorded in 29 patients undergoing surgery during which the posterior tibial nerve was stimulated and SSEP response was recorded from scalp. This method is shown empirically to be more clinically viable than present day approaches. In all 29 cases, the algorithm takes 4sec to extract an SSEP signal, as compared to conventional methods, which take several minutes. The monitoring process using the algorithm was successful and proved conclusive under the clinical constraints throughout the different surgical procedures with an accuracy of 91.5%. Higher accuracy and faster execution time, observed in the present study, in determining the SSEP signals provide a much improved and effective neurophysiological monitoring process.

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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.

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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 frontocentrally
Tiivistelmä 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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41

Smith, Derek Blaine. "Evaluation of various filtering schemes in whitening biological noise for somatosensory evoked potential detection." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq23839.pdf.

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Smith, Derek Blaine. "Evaluation of various filtering schemes in whitening biological noise for somatosensory evoked potential detection." Thesis, University of New Brunswick, 1996. http://hdl.handle.net/1882/539.

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De, Luca Gianluca. "Adaptive noise cancellation of stimulus artifact during somatosensory evoked potential measurements using non-linear filters." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0005/MQ35487.pdf.

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De, Luca Gianluca. "Adaptive noise cancellation of stimulus artifact during somatosensory evoked potential measurements using non-linear filters." Thesis, University of New Brunswick, 1997. http://hdl.handle.net/1882/660.

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45

Endisch, Christian [Verfasser]. "Cortical somatosensory evoked potential amplitudes and severity of hypoxic-ischemic encephalopathy after cardiac arrest / Christian Endisch." Berlin : Medizinische Fakultät Charité - Universitätsmedizin Berlin, 2021. http://d-nb.info/123498234X/34.

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46

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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Oi, Kazuki. "Low-dose perampanel improves refractory cortical myoclonus by the dispersed and suppressed paroxysmal depolarization shifts in the sensorimotor cortex." Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/263565.

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48

Hoeltzell, Perry Bruno. "The temporal and spatial organization of the evoked potential in the cat somatosensory cortex : a voltage and a current source density analysis." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=70162.

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This thesis describes the temporal and spatial organization of the somatosensory evoked potential in the cat in response to small punctate mechanical stimuli applied to the forepaw. The evoked potential was shown to be spatially and temporally stable as well as stationary.
The results of the analysis showed that the evoked potential profiles recorded as a function of cortical depth are the product of an interaction between two populations of neurons, each temporally and spatially distinct from the other. Each population could be activated independently of the other. Each were active at the focus of the potentials. There they produced the classical evoked potential characterized by a reversing polarity as a function of depth. Elsewhere in cortex the populations interacted differently and it was possible to separate the contribution of each.
The current source density method defined the dimensions of the active populations with a precision not available from the potential field analysis thereby confirming their existence and specifying their origins more accurately.
In the discussion, a model is proposed that takes into account these findings in the context of current knowledge of the neuronal connections in the somatosensory cerebral cortex.

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Rundshagen, Ingrid. "Welchen Beitrag können somatosensorisch evozierte Potentiale zur Bestimmung der Narkosetiefe leisten?" Doctoral thesis, Humboldt-Universität zu Berlin, Medizinische Fakultät - Universitätsklinikum Charité, 2002. http://dx.doi.org/10.18452/13841.

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Die Überwachung des zentralen Nervensystems (ZNS) während der Allgemeinanästhesie ist aus anästhesiologischer Sicht wünschenswert, um eine Über- oder Unterdosierung von Narkotika intraoperativ zu vermeiden. Narkosetiefe wird definiert als die Summe aller intraoperativ auf den Patienten einwirkenden sensorischen Stimuli und den zentralnervös dämpfenden Effekten der Anästhetika auf die zerebrale Aktivität. Während für die akustisch evozierten Potentiale diskutiert wird, ob sie die hypnotische Komponente der Allgemeinanästhesie erfassen, ist derzeit unklar, welchen Beitrag somatosensorisch evozierten Potentialen bei der Bestimmung von Narkosetiefe leisten können. Somatosensorisch evozierte Potentiale werden in der klinischen Routine zur Überwachung der Integrität von neuronalen Leitungsbahnen bei Operationen eingesetzt. Das Ziel der hier vorgestellten klinischen Untersuchungen, in denen somatosensorisch und akustisch evozierte Potentiale (SEP, AEP) als mögliche Parameter zur Quantifizierung von Narkosetiefe gegenübergestellt werden, bestand darin, nachfolgende Hypothesen zu überprüfen: 1. Die mittleren Komponenten von SEP und AEP verändern sich dosisabhängig in Abhängigkeit vom Narkotikum in Amplituden und Latenzen und eignen sich als Parameter zur Quantifizierung von Narkotikawirkungen auf das ZNS. 2. Die durch Anästhetika induzierten Veränderungen von SEP und AEP sind unter chirurgischer Stimulation reversibel. Daher eignen sich SEP und AEP als Parameter zur Quantifizierung von Narkosetiefe. 3. SEP und AEP sind geeignet, bei kritisch kranken Patienten den Grad der Analgosedierung quantitativ zu erfassen. 4. SEP und AEP lassen Rückschlüsse auf die Modulation kognitiver Prozesse unter Narkotika zu. In mehreren klinischen Studien an narkotisierten oder analgosedierten Patienten (n = 161) wurden die Wirkungen von Anästhetika auf SEP und AEP dokumentiert, bzw. der Einfluß von chirurgischen oder pflegerischen Maßnahmen untersucht. Zielvariablen waren die Mittellatenz-Komponenten der SEP (N20, P25, N35, P45, N50) und der AEP (Na, Pa; Nb) im Vergleich zur klinischen Einschätzung der Narkosetiefe und den hämodynamischen Daten. Die statistische Analyse wurde mittelts multivariater Analysen durchgeführt, die prädiktive Aussagekraft anhand der prediction probability nach Smith berechnet. Unter Anästhetikagabe fand sich als grundlegendes Muster sowohl bei den SEP als auch bei den AEP eine Verlängerung der Latenzen bei Verminderung der korrespondierenden Amplituden, wobei die Effekte auf die späteren Komponenten > 35 ms deutlicher ausgeprägt waren. Während der Aufwachphase aus der Anästhesie, unter chirurgischen und pflegerischen Maßnahmen waren die anästhetikabedingten Veränderungen der EP-Komponenten teilweise reversibel. Darüberhinaus ließen die SEP-Latenzen P45 und N50 und die AEP-Latenz Nb während der Aufwachphase aus der Anästhesie Rückschlüsse auf die Wiederkehr des expliziten Erinnerungsvermögens nach Narkose zu. Im Gegensatz zu signifikanten Effekten im Gruppenvergleich war die prädiktive Aussagekraft der EP-Parameter im Individualfall gering. SEP sind unter den hier gewählten Narkotikaregimes geeignet, die Modulation der zerebralen Aktivität unter Anästhetika abzubilden. Im Sinne kortikaler Arousalreaktionen werden unter exogener Stimulation die durch Anästhetika induzierten Veränderungen der SEP teilweise antagonisiert. Bei der Interpretation der Befunde in Hinblick auf den Grad der Narkosetiefe ist zu berücksichtigen, daß die Effekte nicht unabhängig vom Anästhetikum sind und im Individualfall stark variieren können. Dennoch ist im Einzelfall der Einsatz von SEP als Monitor zur Narkosetiefe durchaus sinnvoll, z. B. wenn AEP oder andere Verfahren nicht durchführbar sind. Ein Einsatz der SEP als "idealer" Monitor zur Bestimmung des Grades der Narkosetiefe in der klinischen Routine ist zum jetzigen Zeitpunkt sicher nicht gerechtfertigt. Zweifelsohne können weitere Untersuchungen mit SEP zu wesentlichen Erkenntnissen in der klinisch anästhesiologischen Grundlagenforschung beitragen.
Monitoring of the functional state of the central nervous system is of major concern for the anaesthetist to avoid over- or undermedication with the possible sequelae for the patient during general anaesthesia. Depth of anaesthesia is defined as the sum of all excitatory stimuli during operation and the depressant effects of anaesthetics on the electrical activity of the brain. Currently it is discussed, whether the auditory evoked responses (AER) reflect the hypnotic component during anaesthesia. In contrast there is limited information about somatosensory evoked responses (SER) with respect to depth of anaesthesia, even though SER are used to monitor the integrity of the somatosensory pathway at risk during surgery. The aim of the present clinical investigations, in which SER and AER were investigated as parameters to quantify depth of anaesthesia, was to test the following hypotheses: 1. Anaesthetics induce dose-related changes in somatosensory and auditory evoked responses and quantify the anaesthetic action on the brain. 2. During surgical stimulation the anaesthetic induced changes are reversed in part. Therefore SERs and AERs are indicators of depth of anaesthesia. 3. SERs and AERs quantify the grade of analgosedation in critically ill patients. 4. SERs and AERs indicate modulation of cognitive function during recovery from anaesthesia. In clinical studies (n = 161 patients) we investigated the midlatency components of SER and AER during different anaesthetic drug combinations, their modulation during surgical stimulation or nursing care and during recovery from anaesthesia. The midlatency SER components N20, P25, N35, P45 and N50 and the AER components Na, Pa and Nb were studied in relation to the clinical assessment of anaesthetic depth and haemodynamic parameters. Statistical analyses were performed by multivariate analyses of variance for repeated measurements and by the calculation for the prediction probability according to Smith. Results: The main pattern of anaesthetic induced changes on midlatency SER and AER waves was as follows: Prolongation in the latencies and reduction of the corresponding amplitudes. The effect was more pronounced on the components > 35 ms. During recovery from general anaesthesia, during surgical stimulation or nursing care the anaesthetic induced changes were in part reversed. Moreover, changes of the SER components P45 and N50 and the AER component Nb differed in patients with respect to explicit memory performance during the wake-up phase from general anaesthesia. While the group effects were significant, the calculated values of the prediction probability indicated a low predictive potency for the individual case. Conclusions: The midlatency SER waves are indicative for changes in the electrical brain activity during different anaesthetic drug combinations. During surgery or other types of exogeneous intervention the anaesthetic induced changes of some SER and AER components are reversed indicating cortical arousal. Interpreting the results with respect to measure depth of anaesthesia it is important to know, that the changes of the evoked responses are dependent on the used anaesthetic and may differ markedly inter- and intraindividually. In a single case SER-recording can be useful to monitor anaesthetic depth, if e.g. AER monitoring is not possible. However, at the present time SER are not advocated as an "ideal" monitor to measure the level of anaesthesia during clinical routine. Without doubt further investigation elucidating the relation between SER and anaesthetics will contribute to our basic understanding of anaesthetic action on the brain.

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50

Martínez, Jauand Mercedes. "Factores genéticos y psicosociales implicados en la modulación del dolor." Doctoral thesis, Universitat de les Illes Balears, 2013. http://hdl.handle.net/10803/125008.

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Abstract:

La La sensibilidad al dolor y el riesgo sufrir dolor crónico representan fenómenos complejos de naturaleza multidimensional, con una importante variabilidad interindividual. El objetivo de esta tesis doctoral se centró en explorar los factores genéticos y psicosociales implicados en la modulación del dolor y el riesgo a sufrir dolor crónico mediante seis estudios. Los dos primeros exploraron el efecto de factores genéticos y de la edad de inicio de la menopausia en la sensibilidad al dolor en pacientes con fibromialgia en comparación con voluntarias sanas. El primer estudio reveló un incremento de la frecuencia de alelos asociados a una reducida actividad de la enzima COMT en pacientes con síndrome de fibromialgia, junto con una elevada sensibilidad al dolor en estos grupos. El segundo estudio mostró que las pacientes con fibromialgia presentaron una edad de inicio de la menopausia más temprana que las controles. Asimismo, se encontró que las pacientes con menopausia temprana mostraban mayor sensibilidad al dolor que las pacientes con aparición tardía de la menopausia. Los dos siguientes examinaron el papel de factores genéticos en la actividad metabólica cerebral asociada al dolor, la respuesta de analgesia por placebo y en una tarea de funciones ejecutivas. El tercer estudio reveló que el alelo met66 del polimorfismo Val66Met en el gen BDNF se asociaba a un fenotipo de vulnerabilidad, resistencia a la analgesia por placebo, incrementos en la actividad dopaminérgica durante el procesamiento de dolor y reducciones durante la condición placebo. Asimismo, se observó que estos efectos eran dependientes del género del sujeto, con una mayor exacerbación en mujeres y con efectos nulos en hombres. El cuarto estudio mostró aumentos en la actividad del sistema opioide asociados a la respuesta de analgesia por placebo en portadores del alelo C del polimorfismo funcional C385A del gen FAAH. Por otro lado, no se encontraron diferencias significativas debidas a este polimorfismo en la respuesta al dolor en ausencia de placebo, ni en la activación del sistema dopaminérgico. Finalmente, los dos últimos estudios exploraron la modulación social analizando cambios en la actividad eléctrica cerebral como consecuencia de la observación de dolor y tacto en otros. El quinto estudio mostró diferencias en los potenciales evocados visuales en función de la percepción de expresiones faciales de dolor y enfado. El sexto estudio reveló que la observación de experiencias somatosensoriales dolorosas y no dolorosas en otras personas modulaba la amplitud de los potenciales somatosensoriales. Todos estos datos subrayan la naturaleza multidimensional de la respuesta al dolor y resaltan el papel de los factores genéticos y psicosociales en la persistencia del dolor a lo largo del tiempo.
Pain sensitivity and risk for chronic pain constitute complex multidimensional phenomena that vary significantly among individuals. The objective of the present Doctoral Thesis was focused on exploring genetic and psychosocial factors involved in the modulation of pain and chronic pain risk throughout six studies. The first two studies explored the effect of genetic factors and age-of-onset of menopause in pain sensitivity in fibromyalgia patients as compared to healthy volunteers. The first study showed an increased frequency of alleles associated with a reduced activity of COMT enzyme in patients with fibromyalgia syndrome, coupled with high sensitivity to pain in these groups. The second study showed that patients with fibromyalgia had an ageof- onset of menopause earlier than controls. We also found that patients with early menopause showed higher pain sensitivity than patients with late age-of-onset of menopause. The next two studies explored brain metabolic activity in response to pain and placebo analgesia and during an executive function task. The third study revealed that met66 allele of the Val66Met polymorphism in the BDNF gene was associated with a phenotype of vulnerability, strength, placebo analgesia, increases in dopaminergic activity during the processing of pain and reductions during the placebo condition. It was also noted that these effects were dependent on gender, being exacerbated in women as compared to men. The fourth study showed increases in placebo analgesia and in placebo-induced opioid activity in the C385 allele of the functional polymorphism C385A of the FAAH gene. Furthermore, there were no significant differences due to this polymorphism in the pain response in absence of placebo, or in dopaminergic system activation. Finally, the latter two studies explored the social modulation of brain electrical activity during observation of pain and somatosensory experiences in other´s. The fifth study showed differences in visual evoked potentials during the sight of pain and anger faces. The sixth study showed that observation of painful and non-painful experiences in others modulated the amplitude of somatosensory evoked potentials in the onlooker. These data underscore the multidimensional nature of pain response and highlight the role of genetic and psychosocial factors in the persistence of pain.

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Dissertations / Theses on the topic 'Somatosensory evoked potentials'

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