Tesi sul tema "Compound action potential"
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Murnane, Owen D., Beth A. Prieve e Evan M. Relkin. "Recovery of the Human Compound Action Potential Following Prior Stimulation". Digital Commons @ East Tennessee State University, 1998. https://dc.etsu.edu/etsu-works/1793.
Testo completoAbstract (sommario):
The recovery from prior stimulation of the compound action potential (CAP) was measured using a forward masking stimulus paradigm in four normal-hearing, human subjects. The CAP was recorded using a wick electrode placed on the tympanic membrane. The effects of a 4000-Hz, 97-dB SPL conditioning stimulus on CAP amplitude in response to a 4000-Hz probe were measured as a function of conditioner–probe interval for three probe levels. The normalized probe response amplitude was completely recovered to the control values at an average conditioner–probe interval of 1359 ms, similar to that observed in chinchilla (Relkin, E.M., Doucet, J.R., Sterns, A., 1995. Recovery of the compound action potential following prior stimulation: evidence for a slow component that reflects recovery of low spontaneous-rate auditory neurons, Hear. Res. 83, 183–189). The present results are interpreted as a consequence of the slow recovery of low spontaneous-rate (SR), high threshold neurons from prior stimulation (Relkin, E.M., Doucet, J.R., 1991. Recovery from prior stimulation. I: Relationship to spontaneous firing rates of primary auditory neurons. Hear. Res. 55, 215–222) and may provide indirect physiological evidence for the existence of a class of low-SR auditory neurons in humans.
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Jiang, Dan. "Cochlear compound action potential and pathology following kanamycin ototoxity in the guinea pig". Thesis, Keele University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359039.
Testo completo
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Novak, Kevin Richard. "EFFECTS OF SEPSIS ON NERVE EVOKED RESPONSES". Wright State University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=wright1216123137.
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Schweinzger, Ivy A. "Examining the Physiologic Phenotype of Cochlear Synaptopathy Using Narrowband Chirp-Evoked Compound Action Potentials". University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1573811742950316.
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Linke, Theresa [Verfasser], Uwe [Gutachter] Baumann e Andreas [Gutachter] Bahmer. "On the relation of electrophysiological compound action potential (ECAP) measurements and perceptive skills in cochlear implant (CI) listeners / Theresa Linke ; Gutachter: Uwe Baumann, Andreas Bahmer". Frankfurt am Main : Universitätsbibliothek Johann Christian Senckenberg, 2017. http://d-nb.info/1139358650/34.
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Chiou, Li-Kuei. "The effect that design of the Nucleus Intracochlear Electrode Array and age of onset of hearing loss have on electrically evoked compound action potential growth and spread of excitation functions". Diss., University of Iowa, 2016. https://ir.uiowa.edu/etd/3060.
Testo completoAbstract (sommario):
The purpose of this study was to investigate how design changes in Cochlear Nucleus cochlear implants (CIs) (CI24M, CI24R, CI24RE and CI422) affected electrode impedance and ECAP measures, and to determine if these design changes affected post-lingually deafened adults and children with congenital hearing loss in a similar way.
Results of this study showed that electrode impedance was inversely related to the area of the electrode contacts in the array: lowest for the full-banded CI24M CI and highest for adults who used the CI422 device which has the smallest electrode contacts of all four devices. The noise floor of the NRT system likely plays a significant role in the finding that CI users with older devices (the CI24M, and CI24R CIs) had higher ECAP thresholds than individuals with the CI24RE electrode array. The position of the electrode array in the cochlea was also found to have a significant effect on ECAP measures. CI users with modiolar hugging (the CI24R and CI24RE CIs) electrode arrays were found to have lower ECAP thresholds than CI users whose electrode arrays were seated more laterally in the cochlear duct (e.g. the CI24M and CI422 implants). The position of the electrode contacts relative to the modiolus of the cochlea was found to be related to slope of the ECAP growth functions. The lowest slopes were found in CI24RE users. It also had a significant impact on the width of the channel interaction function. Electrode arrays seated further from the modiolus have significantly more channel interaction than electrode arrays that hug the modiolus of the cochlea.
Differences between results recorded from post-lingually deafened adults and children with congenital hearing loss were minimal. The difference only reflected on the ECAP slopes. Slopes in children with congenital hearing loss were significantly steeper than those recorded from adults. This may indicate that children with congenital hearing loss may have better neural survival than adults with acquired hearing loss.
In conclusion, the results of the current study show evidence of the effects of variations in design and function of the implanted components of the Nucleus CI. Perhaps the most significant finding from the current data set is that electrode arrays located closer to the modiolus of the cochlea have lower thresholds and exhibit less channel interaction than electrode arrays that are positioned more laterally. An argument could be made that lower stimulation levels and less channel interaction may result in better outcomes and/or longer battery life. For CI candidates who do not have significant residual acoustic hearing, the CI24RE implant might be a better choice than the more recently introduced CI422 electrode array.
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Scheperle, Rachel Anna. "Relationships among peripheral and central electrophysiological measures of spatial / spectral resolution and speech perception in cochlear implant users". Diss., University of Iowa, 2013. https://ir.uiowa.edu/etd/5055.
Testo completoAbstract (sommario):
The ability to perceive speech is related to the listener's ability to differentiate among frequencies (i.e. spectral resolution). Cochlear implant users exhibit variable speech perception and spectral resolution abilities, which can be attributed at least in part to electrode interactions at the periphery (i.e. spatial resolution). However, electrophysiological measures of peripheral spatial resolution have not been found to correlate with speech perception. The purpose of this study was to systematically evaluate auditory processing from the periphery to the cortex using both simple and spectrally complex stimuli in order to better understanding the underlying processes affecting spatial and spectral resolution and speech perception.
Eleven adult cochlear implant users participated in this study. Peripheral spatial resolution was assessed using the electrically evoked compound action potential (ECAP) to measure channel interaction functions for thirteen probe electrodes. We evaluated central processing using the auditory change complex (ACC), a cortical response, elicited with both spatial (electrode pairs) and spectral (rippled noise) stimulus changes. Speech perception included a vowel-discrimination task and the BKB-SIN test of keyword recognition in noise. We varied the likelihood of electrode interactions within each participant by creating three experimental programs, or MAPs, using a subset of seven electrodes and varying the spacing between activated electrodes. Linear mixed model analysis was used to account for repeated measures within an individual, allowing for a within-subject interpretation. We also performed regression analysis to evaluate the relationships across participants.
Both peripheral and central processing abilities contributed to the variability in performance observed across CI users. The spectral ACC was the strongest predictor of speech perception abilities across participants. When spatial resolution was varied within a person, all electrophysiological measures were significantly correlated with each other and with speech perception. However, the ECAP measures were the best single predictor of speech perception for the within-subject analysis, followed by the spectral ACC. Our results indicate that electrophysiological measures of spatial and spectral resolution can provide valuable information about perception. All three of the electrophysiological measures used in this study, including the ECAP channel interaction functions, demonstrated potential for clinical utility.
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Brown, Daniel. "Origins and use of the stochastic and sound-evoked extracellular activity of the auditory nerve". University of Western Australia. Dept. of Physiology, 2007. http://theses.library.uwa.edu.au/adt-WU2008.0082.
Testo completoAbstract (sommario):
[Truncated abstract] The present study investigated whether any of the characteristics of the compound action potential (CAP) waveform or the spectrum of the neural noise (SNN) recorded from the cochlea, could be used to examine abnormal spike generation in the type I primary afferent neurones, possibly due to pathologies leading to abnormal hearing such as tinnitus or tone decay. It was initially hypothesised that the CAP waveform and SNN contained components produced by the local action currents generated at the peripheral ends of the type I primary afferent neurones, and that changes in these local action currents occurred due to changes in the membrane potential of these neurones. It was further hypothesised that the lateral olivo-cochlear system (LOCS) efferent neurones regulate the membrane potential of the primary afferent dendrites to maintain normal action potential generation, where instability in the membrane potential might lead to abnormal primary afferent firing, and possibly one form of tinnitus. We had hoped that the activity of the LOCS efferent neurones could be observed through secondary changes in the CAP waveform and SNN, resulting from changes in the membrane potential of the primary afferent neurones. The origins of the neural activity generating the CAP waveform and SNN peaks, and the effects of the LOCS on the CAP and SNN were experimentally investigated in guinea pigs using lesions in the auditory system, transient ischemia and asphyxia, focal and systemic temperature changes, and pharmacological manipulations of different regions along the auditory pathway. ... Therefore, the CAP and SNN are altered by changes in the propagation of the action potential along the primary afferent neurones, by changes in the morphology of the tissues surrounding the cochlear nerve, and by changes in the time course of the action currents. If the CAP waveform is not altered, the amplitude of the 1kHz speak in the spontaneous SNN can be used as an objective measure of the spontaneous firing rate of the cochlear neurones. However, because the SNN contains a complex mixture of neural activity from all cochlear neurones, and the amplitude of the spontaneous SNN is variable, it would be difficult to use the spontaneous SNN alone as a differential diagnostic test of cochlear nerve pathologies. To record extratympanic electrocochleography (ET ECochG) from humans, a custom-designed, inexpensive, low-noise, optically isolated biological amplifier was built. Furthermore, a custom-designed extratympanic active electrode and ear canal indifferent electrode were designed, which increased the signal-to-noise ratio of the ECochG recording by a factor of 2, decreasing the overall recording time by 75%. The human and guinea pig CAP waveforms recorded in the present study appeared similar, suggesting that the origins of the human and guinea pig CAP waveforms were the same, and that experimental manipulations of the guinea pig CAP waveform can be used to diagnose the cause of abnormal human ECochG waveforms in cases of cochlear nerve pathologies.
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La, Rocca Viviana. "Atividade antinociceptiva do geraniol: estudos comportamentaise eletrofisiológicos". Universidade Federal da Paraíba, 2016. http://tede.biblioteca.ufpb.br:8080/handle/tede/9944.
Testo completoAbstract (sommario):
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The high incidence of pain in the general population has encouraged research about this theme. Products derived from plant species have been widely used in the pharmacological treatment of pain relief. Recent studies have reported the important role of monoterpenes, active compounds found in the essential oils of aromatic plants, having relevant analgesic and anti-inflammatory potential. The geraniol (GER) is a monoterpenic alcohol, found in >160 essential oil of plant species, especially Cymbopogon gender. In the literature consulted, several biochemical and pharmacological properties are shown of GER: antitumor, antimicrobial, antiinflammatory, antioxidant, gastric and intestinal protector, neuroprotective and antiarrhythmic. In this study was evaluated the antinociceptive activity of GER, not yet reported, by animal behavioral and electrophysiological in vitro models. Male and female adult Swiss mice were used. Initially the acute toxicity of GER was investigated by calculating the lethal dose 50 (LD50) by intraperitoneal (i.p.) (= 199.9 mg/kg) and oral (p.o.) (> 1 g/kg). In psychopharmacological screening, after the administration of single doses of GER (i.p. and p.o.), behavioral changes were observed indicating a depressant profile on the central nervous system (CNS) and/or peripheral nervous system (SNP), and relevant antinociceptive effect of geraniol. Therefore, more specific antinociceptive property evaluation tests were performed. The GER (12.5, 25 or 50 mg/kg i.p. and 50 or 200 mg/kg p.o.) decreased (p<0.001) the number of abdominal contractions induced by i.p. injection of acetic acid, when compared with the control. The opioid antagonist naloxone (5 mg/kg) administered subcutaneously (s.c.) in mice, subsequently treated with GER (25 mg/kg i.p.), did not reverse its antinociceptive activity. The GER (12.5, 25 and 50 mg/kg i.p.) reduced (p<0.001) paw licking time in the second phase (15-30 min, inflammatory phase) of the formalin test. Also, in the glutamate test was reduced (p<0.01) paw licking time when GER 50 mg/kg i.p. administered. In a subsequent step, it was investigated the effect of GER on the excitability of peripheral nerve fibers through extracellular recording in the sciatic nerve in mice. The GER presented depressant effect of the compound action potential (CAP), which was reversed after washing and recovery period. The GER blocked components of the CAP concentration-dependent manner and exposure time to the drug: 1 mM after 120 min for the first component (Aγ and Aβ fibers) and 0.6 mM after 90 min for the second (Aγ and Aδ fibers). The concentration, which induces 50% inhibition of the peak-to-peak amplitude of the PAC (IC50) for the GER was calculated, being equal to 0.48±0.04 mM. The conduction velocity was also reduced by exposure to GER from the 0.3 mM concentration, for the 1st component [46.18±2.60 m/s to 36.04±1.60 m/s; p<0.05 (n=7)] and the 2nd component [18.37±1.31 m/s to 12.71±0.56 m/s; p<0.001 (n=7)]. In conclusion, the results obtained show that GER has antinociceptive activity, mainly in pain related to inflammation. Participation of the opioid pathway in its mechanism of action is unlikely, but the modulation of glutamatergic neurotransmission in a dose-dependent manner is a possible mechanism. Its antinociceptive activity is also related to the reduction in peripheral neuronal excitability, firstly in thinner fibers Aδ, which are directly connected to the conduction pain.
A elevada incidência da dor na população em geral tem incentivado as pesquisas entorno desse tema. Produtos oriundos de espécies vegetais têm sido amplamente utilizados no tratamento farmacológico de alívio da dor. Estudos recentes têm relatado o importante papel dos monoterpenos, princípios ativos encontrados nos óleos essenciais de plantas aromáticas, tendo relevante potencial analgésico e anti-inflamatório. O geraniol (GER) é um álcool monoterpênico, encontrado no óleo essencial de >160 espécies vegetais, especialmente do gênero Cymbopogon. Na literatura consultada, pesquisas apontam várias propriedades bioquímicas e farmacológicas para o GER: antitumoral, antimicrobiana, anti-inflamatória, antioxidante, de proteção gástrica e intestinal, neuroprotetora e antiarrítmica. Neste estudo foi avaliada a atividade antinociceptiva do GER, ainda não relatada, mediante modelos animais comportamentais e eletrofisiológicos in vitro. Foram utilizados camundongos machos e fêmeas Swiss adultos. Inicialmente, foi investigada a toxicidade aguda do GER mediante cálculo da dose letal 50 (DL50) pela via intraperitoneal (i.p.) (=199,9 mg/kg) e oral (v.o.) (>1 g/kg). Na triagem psicofarmacológica, após a subministração de doses únicas de GER (i.p. e v.o.) foram observadas alterações comportamentais que indicaram perfil depressor do sistema nervoso central (SNC) e/ou periférico (SNP), e relevante efeito antinociceptivo do geraniol. Portanto, foram realizados testes comportamentais de avaliação de propriedade antinociceptiva mais específicos. O GER (12,5; 25 e 50 mg/kg i.p. e 50 ou 200 mg/kg v.o.) reduziu (p<0,001) o número de contorções abdominais induzidas por injeção i.p. de ácido acético, quando comparado com o controle. O antagonista opióide naloxona (5 mg/kg) administrado pela via subcutânea (s.c.) em camundongos, subsequentemente tratados com GER (25 mg/kg i.p.), não reverteu sua atividade antinociceptiva. O GER (12,5; 25 e 50 mg/kg i.p.) reduziu (p<0,001) o tempo de lambida da pata na segunda fase (15-30 min, fase inflamatória) do teste da formalina. Também, no teste do glutamato houve redução (p<0,01) do tempo de lambida da pata quando administrado GER 50 mg/kg i.p. Em uma etapa subsequente, investigou-se o efeito do GER sobre a excitabilidade de fibras nervosas periféricas, mediante registro extracelular em nervo ciático de camundongo. O GER apresentou efeito depressor do potencial de ação composto (PAC), o qual foi parcialmente revertido após lavagem durante o período de recuperação. O GER bloqueou as componentes do PAC, de maneira dependente da concentração e do tempo de exposição à droga: 1 mM aos 120 min para a primeira componente (fibras Aγ e Aβ) e 0,6 mM aos 90 min para a segunda (fibras Aγ e Aδ). Foi calculada para o GER, a concentração que induz 50% de inibição da amplitude pico-a-pico do PAC (CI50), sendo igual a 0,48±0,04 mM. A velocidade de condução também, foi reduzida pela exposição ao GER, a partir da concentração de 0,3 mM para a 1ª componente [46,18±2,60 m/s para 36,04±1,60 m/s; p<0,05 (n=7)] e para a 2ª componente [18,37±1,31 m/s para 12,71±0,56 m/s; p<0,001 (n=7)]. Em conclusão, os resultados obtidos mostram que o GER tem atividade antinociceptiva, principalmente na dor relacionada à inflamação. A participação da via opióide no seu mecanismo de ação é pouco provável, mas a modulação da neurotransmissão glutamatérgica de maneira dependente da dose é um mecanismo possível. Sua atividade antinociceptiva tambèm, está relacionada à redução da excitabilidade neuronal periférica, primeiramente de fibras mais finas como Aδ, ligadas diretamente à condução da dor.
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Dhuldhoya, Aayesha Narayan. "Characterization of Temporal Interactions in the Auditory Nerve of Adult and Pediatric Cochlear Implant Users". Diss., University of Iowa, 2013. https://ir.uiowa.edu/etd/4838.
Testo completoAbstract (sommario):
Current cochlear implant systems use fast pulsatile stimulation to deliver the temporal modulations of speech and to, potentially, improve the neural representation of such modulations by restoring the independence of neural firing. The realization of these benefits may vary with other pulse rate-dependent temporal interactions that occur at the neural membrane, e.g., per(i)stimulatory adaptation and its post-stimulatory or forward masking effects. This study attempted to characterize adaptation and recovery of the electrically evoked compound action potential (ECAP) using probe pulses delivered within and following brief (100 ms) high-rate masker (1800 pps) pulse trains at various current levels in adults and children.
With this stimulus paradigm, the ECAP amplitude typically achieved a steady state during the course of pulse train stimulation. The ECAP amplitude at steady state was, on average, a similar proportion (50-70%) of the amplitude at onset for various stimulus levels and in both age groups. However, long-term adaptation effects, evidenced by the decrease in onset ECAP amplitude, were greater in adults particularly at lower levels in the ECAP dynamic range. Instances of alternation in ECAP amplitude were seen at stimulus levels that were higher in the ECAP dynamic range.
The forward masking effects of pulse train stimulation were quantified by the ECAP amplitude in response to a subsequent probe pulse normalized by the response to the same pulse presented alone. Pulse train forward masking increased with the level of the masker pulse train and decreased with the level of the probe stimulus. The recovery of the ECAP for probes that were lower in level than the masker pulse train was incomplete at 600 ms after masker offset, consistent with long-term cumulative effects observed in the response to the probe alone. Masker pulse trains that are lower in level than the probe pulse produced proportionally small decrements in the ECAP amplitude with complete recovery within 250 ms of pulse train offset particularly in adults. ECAP recovery of a probe preceded by a masker pulse train of equal level followed a monotonic or non-monotonic pattern consistent with a hypothesis of both adaptation and facilitation occurring with pulse train stimulation. The various patterns of recovery may attest to the occurrence of more than a single process in the same subset of nerve fibers or in different fibers. We hypothesize that the variations in the recovery patterns may be attributable to individual differences in the status of the auditory nerve and possibly, the variations in temporal interactions across the spatial domain at different stimulus levels.
Finally, the probe-evoked ECAP amplitude at steady state in children and briefly, e.g., 20 ms, after pulse train offset in both age groups could be predicted by the ECAP amplitude in response to the same probe pulse when preceded at a brief interval (1.2 or 2 ms) by a single masker pulse of the same level as the masker pulse train.
Further investigation may reveal if the observed differences in neural responsiveness to pulsatile stimulation, among individuals account for differences in psychophysical measures, including speech perception and whether there may be an "optimal" neural output that could be evoked by an individually "optimized" signal.
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Batrel, Charlène. "Nouvelle méthode d'exploration fonctionnelle du nerf auditif". Thesis, Montpellier 1, 2014. http://www.theses.fr/2014MON13520/document.
Testo completoAbstract (sommario):
Contexte: La réponse synchrone des fibres auditives, évaluée à partir de l'onde I des potentiels d'action évoqués auditifs (PEA), ou à partir du potentiel d'action composite (PAC) du nerf auditif, est l'élément clé du dépistage des neuropathies auditives. De récentes études ont toutefois montré que le seuil et l'amplitude de cette réponse pouvaient être absolument normaux malgré une perte importante de fibres du nerf auditif. Dans ce travail de thèse, nous proposons une nouvelle méthode d'exploration fonctionnelle, potentiellement applicable à l'homme, rendant mieux compte du nombre et de l'intégrité des fibres du nerf auditif. Cette méthode a été évaluée à l'aide d'un modèle pharmacologique de neuropathie physiologiquement pertinent.Matériel et méthodes: Chez des gerbilles, une perte sélective de fibres auditives a été induite par application d'une faible concentration d'ouabaïne dans la niche de la fenêtre ronde de la cochlée. Cette neuropathie a ensuite été caractérisée par des comptages de synapses (immunohistochimie/imagerie confocale 3D) et l'enregistrement de l'activité unitaire de fibres du nerf auditif. Les PAC et l'activité soutenue du nerf ont été enregistrés 6 jours après l'application d'ouabaïne, à l'aide d'une électrode de recueil disposée dans la niche de la fenêtre ronde. Résultats: L'application d'ouabaïne induit une perte spécifique des fibres à basse activité spontanée (AS<0,5 potentiel d'action/sec) comme observé au cours du vieillissement et après une surexposition sonore. La disparition de cette population de fibres est indétectable à l'aide du PAC car leur réponse unitaire est à la fois retardée et désynchronisée. Par contre, l'amplitude de la réponse soutenue du nerf se révèle être un bien meilleur indicateur de la perte des fibres à basse activité spontanée. Pour aller plus loin, nous avons mis au point une méthode qui permet d'observer l'activité synchrone et soutenue du nerf auditif dans une même réponse. Cette approche rend compte des trois mécanismes de fusion vésiculaire (libération rapide, lente et soutenue) de la première synapse auditive.Conclusion: L'analyse de la réponse soutenue du nerf auditif est une approche fiable pour déterminer le nombre et le phénotype fonctionnel des fibres qui composent le nerf auditif. Cette méthode, applicable à l'homme, devrait améliorer le dépistage des neuropathies, avec une meilleure différenciation des atteintes d'origine synaptique et/ou neuronale.Mots clés: Cochlée, nerf auditif, potentiel d'action composite, activité soutenue du nerf auditif, enregistrement unitaires, ouabaïne, neuropathieBackground: The synchronous activation of the auditory nerve fibers (ANFs), is commonly studied through the compound action potential (CAP), or the auditory brainstem responses (ABR), to probe deafness in experimental and clinical settings. Recent studies have shown that substantial ANF loss can coexist with normal hearing threshold, and even unchanged CAP amplitude, making the detection of auditory neuropathies difficult. In this study, we took advantage of the round window neural noise (RWNN) to probe ANF loss in a physiologically-relevant model of neuropathy.Material and methods: ANF loss was induced by the application of ouabain onto the round window niche. CAP and RWNN of the gerbil's cochlea were recorded through an electrode placed onto the round window niche, 6 days after the ouabain application. Afferent synapse counts and single-unit recordings were carried-out to determine the degree and the nature of ANF loss, respectively. Results: Application of a low ouabain-dose into the gerbil RW niche elicits a specific degeneration of low spontaneous rate (SR) fibers, as shown by single-unit recordings. Simultaneous recordings (CAP/single-unit) demonstrate that low-SR fibers have a weak contribution to the CAP amplitude because of their delayed and broad first spike latency distribution. However, the RWNN amplitude decreases with the degree of synaptic loss. The RWNN method is therefore more sensitive than CAP to detect low-SR fiber loss, most probably because it reflects the sustained discharge rate of ANFs. Based on these data, we proposed a far-field method (Peri-stimulus time response-PSTR) to assess the fast, slow, and sustain vesicular release at the first auditory synapse.Conclusion: The round window neural noise is a faithful proxy to probe the degree and the SR-based nature of fiber loss. This method could be translated into the clinic to probe hidden hearing loss and orient the practitioner toward synaptopathy and/or neuropathy.Key words: Cochlea, auditory nerve, compound action potential, round window neural noise, single fiber recording, ouabain-induced neuropathy
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Connors, Sean P. "Compounds that prolong the cardiac action potential". Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.670306.
Testo completo
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Botros, Andrew Computer Science & Engineering Faculty of Engineering UNSW. "The application of machine intelligence to cochlear implant fitting and the analysis of the auditory nerve response". Awarded By:University of New South Wales. Computer Science & Engineering, 2010. http://handle.unsw.edu.au/1959.4/44707.
Testo completoAbstract (sommario):
Effective cochlear implant fitting (or programming) is essential for providing good hearing outcomes, yet it is a subjective and error-prone task. The initial objective of this research was to automate the procedure using the auditory nerve electrically evoked compound action potential (the ECAP) and machine intelligence. The Nucleus?? cochlear implant measures the ECAP via its Neural Response Telemetry (NRT) system. AutoNRT, a commercial intelligent system that measures ECAP thresholds with the Nucleus Freedom implant, was firstly developed in this research. AutoNRT uses decision tree expert systems that automatically recognise ECAPs. The algorithm approaches threshold from lower stimulus levels, ensuring recipient safety during postoperative measurements. Clinical studies have demonstrated success on approximately 95% of electrodes, measured with the same efficacy as a human expert. NRT features other than ECAP threshold, such as the ECAP recovery function, could not be measured with similar success rates, precluding further automation and loudness prediction from data mining results. Despite this outcome, a better application of the ECAP threshold profile towards fitting was established. Since C-level profiles (the contour of maximum acceptable stimulus levels across the implant array) were observed to be flatter than T-level profiles (the contour of minimum audibility), a flattening of the ECAP threshold profile was adopted when applied as a fitting profile at higher stimulus levels. Clinical benefits of this profile scaling technique were demonstrated in a 42 subject study. Data mining results also provided an insight into the ECAP recovery function and refractoriness. It is argued that the ECAP recovery function is heavily influenced by the size of the recruited neural population, with evidence gathered from a computational model of the cat auditory nerve and NRT measurements with 21 human subjects. Slower ECAP recovery, at equal loudness, is a consequence of greater neural recruitment leading to lower mean spike probabilities. This view can explain the counterintuitive association between slower ECAP recovery and greater temporal responsiveness to increasing stimulation rate. This thesis presents the first attempt at achieving completely automated cochlear implant fitting via machine intelligence; a future generation implant, capable of high fidelity auditory system measurements, may realise the ultimate objective.
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Xu, Ying. "Antifouling compounds from deep-sea bacteria and their potential mode of action /". View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?BIOL%202009%20XU.
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Iyer, Chitra C. "The Role of Muscle and Nerve in Spinal Muscular Atrophy". The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1451568269.
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Donato, Micheline Freire. "Purificação, caracterização bioquímica e eletrofisiológica da toxina Mic6c7NTX da Peçonha da Serpente Micrurus ibiboboca (Merrem, 1820)". Universidade Federal da Paraíba, 2008. http://tede.biblioteca.ufpb.br:8080/handle/tede/6863.
Testo completoAbstract (sommario):
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Previous issue date: 2008-08-29Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
Snake venoms contain a complex arsenal of protein bio-active components, many of these being neurotoxins (NTXs). These snakes have high neurotoxic activity venom, corresponding to the Elapidae family, which includes coral snakes (Micrurus) whose venom contains circa 90-95% of low molecular mass protein components. Among these, several are postsynaptic neurotoxins or α- NTXs (MM = 6-9 kDa). The Micrurus ibiboboca (Merren, 1820) is a snake of the Elapidae family witch is quite common in the Northeast of Brazil. In spite of the great diversity of species of Micrurus, scarce works involving the nervous system with isolated and pure toxins of those serpents has been developed in level biochemical, pharmacological and electrophysiological. The aim of this study was to purify the toxin Mic6c7NTX of the Micrurus ibiboboca venom, characterize to biochemically and electrophysiologically the toxin Mic6c7NTX in the peripheral nervous system (PNS) of rats, evaluating alterations in the record of the Compound Action Potential (CAP) of the isolate nerve and the toxin activity on the voltage-dependent sodium channels (Nav) in the neurons of the dorsal root ganglion (DRG). The venom was extracted from the Micrurus ibiboboca collected in Paraiba State (Brazil). Initially, electrophysiological tests (current clamp method) using the single sucrose gap technique were accomplished with crude venom (100μg/mL). It was observed that in this concentration the crude venom caused reduction in the CAP amplitude (25%). This neurotoxity led into an intriguing question: what components of the venom would promote to reduction in the excitability of the nerve? Based upon this question, I decided to purify the venom throughout the Liquid Chromatography of the High Performance (HPLC) of the Cation Exchange Chromatography (CIEX) and the Reverse Phase Chromatography (RPC). The molecular mass (MM) of the raw toxin was determined by mass-spectrometry (MALDI-QTOF/ MS) and N-terminal sequence by means of Edman s Degradation. The search for similarity with other toxins was accomplished against proteomic data bank. The CIEX profile showed 19 fractions and the highest peak fraction was used for the second dimension. The toxin Mic6c7NTX obtained by RPC showed elution in 26.7%of the acetonitrile (ACN) and MM 7.047.56Da. The obtained partial N-terminal sequence showed 31 aminoacid residues. The search for similarity of structure and function showed great similarity (65%) with other short chain α-NTXs Australian elapids snakes. The electrophysiological studies (single sucrose gap technique) showed that the toxin Mic6c7NTX (1 μM) reduced the excitability of the isolate nerve similarly to the reduction observed in the crude venom about 21%. Other CAP parameters such as despolarization speed (DSCAP), repolarization time (τCAP) and peak of time (PTCAP) did not show alterations. This suggests that the toxin may be affecting the Nav channels. For the confirmation of that hypothesis experiments were accomplished with whole cell patch-clamp technique in DRG neurons. This results showed that the toxin Mic6c7NTX (1 WM) abolished completely the current of Nav channels sensitive the tetrodotoxin (TTX-S). Also the Nav channels TTX resistant (TTX-R) were investigated in the presence of the Mic6c7NTX toxin previously using TTX (100 nM). This results showed that the toxin Mic6c7NTX (100 nM) abolished completely the current of Nav channels TTX-R and IC50 = 30nM. However, reversion of this blocking was not observed. The present study biochemically and electrophysiologically characterized an α-NTX of the Micrurus ibiboboca elapid snake. Furthermore, it showed a potent toxin with affinity Nav channels TTX-S and TTX-R of the PNS. This is the first α-NTX isolated and identified of the venom from the Micrurus ibiboboca (Merrem, 1820) snake.
As serpentes da família Elapidae possuem uma peçonha com alta atividade neurotóxica e capacidade de letalidade. Fazem parte dessa família as serpentes corais americanas (gênero Micrurus) com suas peçonhas contendo cerca de 90-95% de componentes protéicos, sendo na sua maior parte neurotoxinas com baixa massa molecular (6-8 kDa), podendo ser destacadas as neurotoxinas com ação pós-sinápticas ou α-Neurotoxinas (α-NTX). A Micrurus ibiboboca (Merrem, 1820) é uma serpente da família Elapidae, comum na região Nordeste. Apesar da grande diversidade de espécies do gênero Micrurus sp., escassos trabalhos envolvendo atividade de toxinas isoladas e puras destas peçonhas e sistema nervoso têm sido desenvolvidos em nível bioquímico, farmacológico ou eletrofisiológico. O objetivo desse estudo foi purificar a toxina Mic6c7NTX da peçonha de M. ibiboboca, caracterizar bioquímicamente e investigar com ferramentas eletrofisiológicas a ação da toxina no Sistema Nervoso Periférico (SNP) de ratos avaliando alterações no Potencial de Ação Composto (PAC) do nervo isquiático isolado e a atividade da toxina nos canais para sódio dependentes de voltagem (Nav) em neurônios do gânglio da raiz dorsal (DRG). A peçonha da M. ibiboboca foi extraída de serpentes coletadas no Estado da Paraíba (Brasil). Inicialmente, ensaios eletrofisiológicos com o método de current clamp utilizando a técnica de single sucrose gap foram realizados com a peçonha bruta (100 Wg/mL). Os resultados mostraram que a peçonha bruta nessa concentração promoveu redução na amplitude do PAC (25%). Esse efeito da toxina na excitabilidade do nervo levantou o questionamento: Que componentes da peçonha estariam causando essa diminuição da excitabilidade? A peçonha foi purificada por meio de Cromatografia Líquida de Alta Performance (HPLC), de troca catiônica (CIEX) e fase reversa (RPC). Na sequência, os picos da CIEX foram submetidos à RPC e posteriormente analisados por espectrometria de massas (MALDI-TOF/MS) que detectou a massa molecular da toxina Mic6c7NTX de 7.047,56 Da. Em seguida, foi determinado o seu N-terminal por Degradação de Edman que apresentou 31 resíduos de aminoácidos e serviu de estudo para a bioinformática na busca por similaridade em banco de dados proteômicos com outras toxinas protéicas, demonstrando que a toxina Mic6c7NTX apresentou similaridade (65%) com α-NTXs de cadeia curta de serpentes elapídicas australianas. Posteriormente, foi investigado o efeito da toxina isolada no SNP. Os estudos eletrofisiológicos em single sucrose gap demonstraram que a toxina Mic6c7NTX (1 WM) reduziu a excitabilidade do nervo isolado de forma similar à observada pela peçonha bruta. Não foram observadas alterações significantes em outros parâmetros do PAC, como velocidade de despolarização (VDPAC), tempo de repolarização (τPAC) e tempo de pico (PTPAC), sugerindo que a toxina atuasse num sítio de ligação específico dos [Escreva uma citação do documento ou o 11 canais Nav no SNP. Para a confirmação dessa hipótese foram realizados experimentos de voltage clamp com a técnica de whole cell patch-clamp em cultura primária de neurônios DRG da medula espinhal de ratos. Os resultados mostraram que a toxina Mic6c7NTX (1 WM) aboliu completamente as correntes dos canais Nav sensíveis à tetrodotoxina (TTX-S). Também foi investigado o efeito da toxina sobre a população de canais Nav resistentes à TTX (TTX-R), utilizando previamente TTX (100 nM) para bloquear os canais Nav TTX-S. Os registros com a toxina Mic6c7NTX (100 nM) demonstraram um bloqueio total da corrente nos canais Nav TTX-R dos DRGs e uma IC50 da toxina em torno de 30 nM. Também foi observado que essa toxina se liga aos canais Nav de forma lenta e irreversível. O presente estudo caracterizou bioquímica e eletrofisiologicamente uma α-NTX da serpente elapídica Micrurus ibiboboca. Farmacologicamente, trata-se de uma potente toxina com afinidade aos canais Nav TTX-S e TTX-R do SNP. Essa é a primeira α-NTX isolada e caracterizada da peçonha da serpente Micrurus ibiboboca (Merrem, 1820).
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Stengel, Chloe. "Investigation of the mechanisms of action of sulphamoylated compounds, a potential new class of drug to treat cancer". Thesis, Imperial College London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.506928.
Testo completo
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Radford, Michael T. "A study of Central Florida nonroad VOC and NOx emissions and potential actions to reduce emissions". Orlando, Fla. : University of Central Florida, 2009. http://purl.fcla.edu/fcla/etd/CFE0002850.
Testo completo
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Berezina, Maria Andrey. "Medial olivocochlear efferent (MOC) effects on stimulus frequency otoacoustic emissions (SFOAEs) and auditory-nerve compound action potentials (CAP) in guinea pigs". Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/97822.
Testo completoAbstract (sommario):
Thesis: Ph. D., Harvard-MIT Program in Health Sciences and Technology, February 2015.Cataloged from PDF version of thesis. "February 2015."
Includes bibliographical references.
In humans, SFOAEs can non-invasively assess MOC strength and, may predict the MOC reduction of damage from traumatic sounds. However, the functionally important MOC effect is inhibition of auditory-nerve (AN) responses. Understanding the relationship between MOC effects on SFOAEs and AN CAPs is important for understanding SFOAE generation and for development of clinical tools that use these measures. This thesis presents several novel data sets that address MOC effects on SFOAEs, CAPs and the relationship between them in guinea pigs. Classic theory indicates that SFOAEs come from cochlear irregularities that coherently reflect energy at the peak of the traveling wave (TW), and that reflected energy arrives in the ear canal as a single wave at certain delay. Contrary to theory, in humans and chinchillas there have been reports of SFOAEs having multiple components with different delays, and that lowfrequency SFOAE delays are too short. The first thesis aim used time-frequency analysis to show that guinea pigs have frequency regions over which SFOAEs appear to have multiple components. However, we argue that the multiple components can be a simple result of variations in the patters of irregularities near the TW peak and are not necessarily indicative of multiple SFAOE sources. From comparison of our SFOAE delays with previously reported neural delays, we hypothesize that short SFOAE delays at low frequencies arise from a cochlear motion with a group delay shorter than the TW group delay. Aim 2 investigated how SFOAEs are affected by brainstem electrical stimulation of MOC fibers and found that MOC activation sometimes inhibited and sometimes enhanced SFOAEs. MOC stimulation always decreased CAP sensitivity which rules out SFOAE enhancement from increased cochlear amplification. We propose that shock-evoked MOC activity increases cochlear irregularity which results in increased SFOAE amplitudes. Aim 3 investigated the relationship between MOC effects on SFOAEs and tone-pip-evoked AN CAPs at same frequency and sound level. The ratio of the MOC effect on the SFOAE to the MOC effect on the CAP showed a highly-significant decrease (p<0.001) as the strength of MOC stimulation was increased. Although this observation was unexpected, several hypothesis to explain it are presented.
by Maria Andrey Berezina.
Ph. D.
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Bouarab, Lynda. "Évaluation du potentiel et de voies innovantes de mise en oeuvre de composés phénoliques antimicrobiens d’origine végétale pour la conservation des aliments". Thesis, Lyon, 2018. http://www.theses.fr/2018LYSE1084.
Testo completoAbstract (sommario):
Le règne végétal est une ressource renouvelable d'une large gamme de métabolites secondaires biologiquement actifs. Ces travaux de thèse proposent une stratégie multidisciplinaire d'évaluation du potentiel de composés phénoliques antimicrobiens d'origine végétale pour la conservation des aliments. Un criblage de l'activité antimicrobienne in vitro vis-à-vis de 8 souches de la flore pathogène et d'altération des aliments d'une centaine de molécules pures et une soixantaine d'extraits végétaux a d'abord permis de sélectionner les plus actifs. Différents mécanismes d'action vis-à-vis de S. aureus ont pu être mis en évidence par cytométrie de flux couplée à l'utilisation de marqueurs de l'état physiologique des bactéries pour quelques uns des composés actifs sélectionnés. En vue d'une application à de la viande bovine, l'activité antibactérienne des composés phénoliques ou extraits végétaux les plus actifs a été réévaluée dans des milieux de culture plus complexes mimant leur teneur en protéines et en matières grasses. Les résultats de ce criblage et un suivi microbiologique de viande hachée de bœuf avec 1% (m/m) d'extrait ajouté ont permis d'observer que les pertes d'activité antibactérienne observées étaient notamment corrélées aux interactions des composés phénoliques avec les protéines ou les matières grasses. L'incorporation des composés phénoliques ou extraits végétaux dans des matériaux d'emballage en contact alimentaire a constitué la seconde voie de mise en œuvre envisagée. Des films plastiques conservant une activité antibactérienne ont ainsi pu être élaborés par voie fondueThe plant kingdom is a renewable resource of a wide range of biologically active secondary metabolites. This thesis proposes a multidisciplinary strategy for evaluating the potential of plant-derived antimicrobial phenolic compounds for food preservation. A screening of the antimicrobial activity in vitro against 8 strains of foodborne pathogenic and spoilage microorganisms of a hundred pure molecules and about sixty plant extracts allowed to select the most active. Different mechanisms of action with respect to S. aureus could be demonstrated by flow cytometry coupled with the use of probes of the physiological state of the bacteria for some of the selected active compounds. For application to beef, the antibacterial activity of the most active phenolic compounds or plant extracts has been re-evaluated in more complex culture media mimicking their protein and fat content. The results of this screening and a microbiological monitoring of minced beef with 1% (m / m) of added extract made it possible to observe that the observed losses of antibacterial activity were in particular correlated with the interactions of the phenolic compounds with the proteins or fat. Incorporation of phenolic compounds or plant extracts into packaging materials in contact with food constituted was the second proposed route of implementation. Plastic films that retain antibacterial activity have thus been able to be prepared by melting
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Zhang, Jiaxin. "Syntheses and spectroscopic studies of luminescent surfactant rhenium(I) and ruthenium(II) diimine complexes : potential applications as functional materials for second-harmonic generation and mesoporous silicate formation /". View the Table of Contents & Abstract, 2004. http://sunzi.lib.hku.hk/hkuto/record/B30267791.
Testo completo
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Zhang, Jiaxin, e 張家新. "Syntheses and spectroscopic studies of luminescent surfactant rhenium(I) and ruthenium(II) diimine complexes: potential applications as functional materials forsecond-harmonic generation and mesoporous silicate formation". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2004. http://hub.hku.hk/bib/B45015272.
Testo completo
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Yaacoubi, Abdelrani. "Etude de l'influence d'ions metalliques et de composes organiques sur l'adsorption du dodecyl sulfate de sodium sur charbon actif". Poitiers, 1988. http://www.theses.fr/1988POIT2286.
Testo completoAbstract (sommario):
Les resultats experimentaux (cinetique rapide d'adsorption, parametre d'equilibre des isothermes d'adsorption et variation du potentiel zeta des particules de charbon) montrent une augmentation de la capacite d'adsorption du dodecylsulfate de sodium en presence d'ions metalliques et une inhibition mutuelle de l'adsorption en presence d'alcools aliphatiques et de composes organiques
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Esvan, Yannick. "Conception et synthèse de nouveaux composés hétéroaromatiques inhibiteurs potentiels de kinases". Thesis, Clermont-Ferrand 2, 2016. http://www.theses.fr/2016CLF22743.
Testo completoAbstract (sommario):
Depuis la mise en évidence de l’existence des protéines kinases vers la fin des années 1950 cette famille d’enzymes s’est vu attribuer d’importants rôles dans divers mécanismes pathologiques notamment dans des processus de cancérisations. Plus récemment ces enzymes ont été identifiées comme potentiellement impliquées dans d’autres types de maladies telles que les maladies neurodégénératives.Deux projets de recherche seront présentés. Le premier projet expose la conception et la synthèse de nouveaux composés tricycliques de la famille des pyrido[3,4-g]quinazolines. Les propriétés inhibitrices de kinases des premiers dérivés ont été évaluées sur un panel de cinq kinases (CDK5, CK1, GSK3, CLK1 and DYRK1A) connues pour leurs implications dans la maladie d’Alzheimer. L’intérêt de ces nouveaux squelettes tricycliques comme inhibiteurs de kinases a été validé par des activités inhibitrices nanomolaire à l’encontre des kinases DYRK1A et CLK1. D’autre part l’obtention de structures co-crystallographiques d’interaction de deux dérivés avec le site ATP de la kinase CLK1 a permis de rationnaliser la substitution du motif pyrido[3,4-g]quinazoline. Le second projet présente le développement d’un nouveau dérivé de la staurosporine aglycone (K252c) dans lequel la partie lactame a été remplacée par un noyau pyrazole. Une étude préliminaire des propriétés biologiques de l’indolopyrazolocarbazole obtenu met en avant une cytotoxicité, du même ordre de grandeur que K252c, contre les lignées cellulaires K562 (leucémie humaine) et HCT116 (carcinome du colon). En revanche, le composé chef de file s’est révélé être un faible inhibiteur de cibles connues de K252c, les isoformes α and γ de la protéine kinase C et présente un bon potentiel inhibiteur des kinases Pim 1-3. Ce nouveau chemotype pourrait être un inhibiteur de kinases prometteurIn 1950’s protein kinases were found to play a critical role in cell signaling, rising strong research potential for this enzyme family. Initially investigated for their implications in cancerogenesis they were more recently found to be involved in a wide variety of diseases including neurodegenerative pathologies. Herein will be presented two research projects that offer bright new perspectives for the inhibition of kinases involved whether in neurodegenerative diseases or cancers.First, the design and synthesis of new pyrido[3,4-g]quinazoline derivatives will be described as well as their protein kinase inhibitory potencies toward five CMGC family members (CDK5, CK1, GSK3, CLK1 and DYRK1A) that are known to play a potential role in Alzheimer’s disease. The interest for this original tricyclic heteroaromatic scaffold as modulators of CLK1/ DYRK1A activity was validated by nanomolar potencies. CLK1 co-crystal structures with two inhibitors revealed the binding mode of these compounds within the ATP-binding pocket and led to the synthesis of new diversely substituted pyrido[3,4-g]quinazolines.Then the synthesis of a new derivative of the staurosporine aglycon (K252c), in which the lactam ring was replaced by a pyrazole moiety, will be depicted. The resulting indolopyrazolocarbazole inhibited Pim isoforms 1–3 whereas it did not impair the activity of two known targets of K252c, protein kinase C isoforms α and γ . The lead compound exhibited same cytotoxic activity as K252c toward both human leukemia and colon carcinoma cell lines (K562 and HCT116), strongly suggesting that this new scaffold deserves further investigations for treatment of malignancies associated with kinases activities
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Souabi, Salah. "Etude de l'adsorption de tensioactifs cationiques sur charbon actif influence de coadsorbats /". Grenoble 2 : ANRT, 1988. http://catalogue.bnf.fr/ark:/12148/cb376186543.
Testo completo
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Wang, Shao-Po, e 王韶博. "Modeling Evoked Compound Action Potential and Signal Processing in Cochlear Implant". Thesis, 2003. http://ndltd.ncl.edu.tw/handle/51585449622758054259.
Testo completoAbstract (sommario):
碩士義守大學
電機工程學系
91
ABSTRACT A prosthetic device, called the cochlear implant, can be implanted in the inner ear and can restore partial hearing to profoundly deaf people. According to the clinical data, the effect is vary different from individual. Therefore, improved efficacy to cochlear implant is such a important work. There are two ways can ameliorate the situation. One is to find the new stimulation strategy, the other is to design new electrode dimension over again. When new stimulation strategy or new electrode be developed. Apply to patient is only way to distinguish weather the new design fine or inferior. We are going to find some method called modeling evoked compound action potential in cochlear implant that we can know the performance on new design without any surgery. Currently there is no easy ways to model evoked compound action potential (EAP) of the auditory nerve fibers. This thesis presents a method to model the EAP using finite element method, Schwarz-Eikhof nerve fiber model, and equivalent circuit models on a 3D cochlea model. The simulation results are validated by EAP measured in cochlear implant users.
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Huang, Hau-Shiou, e 黃浩修. "Patient-specific Models based on Evoked Compound Action Potential and Electrical Field Imaging". Thesis, 2016. http://ndltd.ncl.edu.tw/handle/67049380601925852684.
Testo completoAbstract (sommario):
碩士國立交通大學
生醫工程研究所
105
With physiological dimensions of the cochlear implant (CI) patient’s cochlea from computed tomography (CT), it is possible to build a more accurate patient-specific electro-neural model of CI patients based on clinical measurements. One of such methods is proposed in this thesis. An accurate patient specific electro-neural model could be used for fine tuning the electrical stimulation parameters or “maps” of a CI patient without needing many CI mapping sessions. This has enormous implication for CI pediatric applications due to obvious reason. The goal of this thesis is to evaluate the relative spiral ganglion cells (SGC) density of a human CI patient. The electric potential along the cochlea in a CI patient can be measured via electric field imaging (EFI). Also, there is a significant correlation between evoked compound action potential (ECAP) threshold and behavior threshold (T) level for a CI patient. ECAP measurement approach is an objective and faster way to obtain the relative T level of a CI patient. This again has important implication for pediatric CI mapping application since it does not require feedback from pediatric CI patients. Due to a large stimulating range, we propose to use the idea of using “apple-core”-ECAP paradigm which can limit the auditory nerves being stimulated to a narrower volume between neighboring two electrodes. Since the volume of auditory nerves activated and the distance between electrode and SGC are fixed, we can obtain the relative SGC density through comparing with every SGC signal at different electrodes.
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LI, ZHI-CHANG, e 李志昌. "Morphological organization and compound action potential of sacrococcygeal dorsal roots of the rat". Thesis, 1991. http://ndltd.ncl.edu.tw/handle/88921030062421954300.
Testo completo
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ZHAO, FU-SHAN, e 趙福杉. "Analysis of compound action potential and field potential of the nervous syste, and development of a recording system". Thesis, 1992. http://ndltd.ncl.edu.tw/handle/20147015298986728414.
Testo completo
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Muzquiz, Maria I. "Reversible Nerve Conduction Block Using Low Frequency Alternating Currents". Thesis, 2020. http://hdl.handle.net/1805/23576.
Testo completoAbstract (sommario):
Indiana University-Purdue University Indianapolis (IUPUI)This thesis describes a novel method to reversibly and safely block nerve conduction using a low frequency alternating current (LFAC) waveform at 1 Hz applied through a bipolar extrafascicular electrode. This work follows up on observations made on excised mammalian peripheral nerves and earthworm nerve cords. An in-situ electrophysiology setup was used to assess the LFAC waveform on propagating action potentials (APs) within the cervical vagus nerve in anaesthetized Sprague-Dawley rats (n = 12). Two sets of bipolar cuff or hook electrodes were applied unilaterally to the cervical vagus nerve, which was crushed rostral to the electrodes to exclude reflex effects on the animal. Pulse stimulation was applied to the rostral electrode, while the LFAC conditioning waveform was applied to the caudal electrode. The efferent volley, if unblocked, elicits acute bradycardia and hypotension. The degree of block of the vagal stimulation induced bradycardia was used as a biomarker. Block was assessed by the ability to reduce the bradycardic drive by monitoring the heart rate (HR) and blood pressure (BP) during LFAC alone, LFAC with vagal stimulation, and vagal stimulation alone. LFAC applied via a hook electrode (n = 7) achieved 86.6 +/- 11% block at current levels 95 +/- 38 uAp (current to peak). When applied via a cuff electrode (n = 5) 85.3 +/- 4.60% block was achieved using current levels of 110+/-65 uAp. Furthermore, LFAC was explored on larger vagal afferent fibers in larger human sized nerve bundles projecting to effects mediated by a reflex. The effectiveness of LFAC was assessed in an in-situ electrophysiological setup on the left cervical vagus in anaesthetized domestic swine (n = 5). Two bipolar cuff electrodes were applied unilaterally to the cervical vagus nerve, which was crushed caudal to the electrodes to eliminate cardiac effects. A tripolar extrafascicular cuff electrode was placed most rostral on the nerve for recording of propagating APs induced by electrical stimulation and blocked via the LFAC waveform. Standard pulse stimulation was applied to the left cervical vagus to induce the Hering-Breuer reflex. If unblocked, the activation of the Hering-Breuer reflex would cause breathing to slow down and potentially cease. Block was quantified by the ability to reduce the effect of the Hering-Breuer reflex by monitoring the breathing rate during LFAC alone, LFAC and vagal stimulation, and vagal stimulation alone. LFAC achieved 87.2 +/- 8.8% (n = 5) block at current levels of 0.8 +/- 0.3 mAp. Compound nerve action potentials (CNAP) were monitored directly. They show changes in nerve activity during LFAC, which manifests itself as the slowing and amplitude reduction of components of the CNAPs. Since the waveform is balanced, all forward reactions are reversed, leading to a blocking method that is similar in nature to DC block without the potential issues of toxic byproduct production. These results suggest that LFAC can achieve a high degree of nerve block in both small and large nerve bundles, resulting in the change in behavior of a biomarker, in-vivo in the mammalian nervous system at low amplitudes of electrical stimulation that are within the water window of the electrode.
31
Candeias, Rui Dinis Teodoro. "Evaluation of motor neuron excitability by CMAP scanning with modulated current". Master's thesis, 2014. http://hdl.handle.net/10362/14288.
Testo completoAbstract (sommario):
It is important to have better evaluation and understanding of the motor neuron physiology, with the goal to early and objectively diagnose and treat patients with neurodegenerative pathologies. The Compound
Muscle Action Potential (CMAP) scan is a non-invasive diagnosis technique for neurodegenerative pathologies, such as ALS, and enables a quick analysis of the muscle action potentials in response to motor nerve stimulation. This work aims to study the influence of different pulse modulated waveforms in peripheral nerve excitability by CMAP scan technique on healthy subjects.
A total of 13 healthy subjects were submitted to the same test. The stimuli were applied in the medium nerve on the right wrist and electromyography signal collected on the Abductor Pollicis Brevis (APB) muscle surface on the right thumb. Stimulation was performed with an increasing intensities range from 4 to 30 mA, with varying steps, 3 stimuli per step. The procedure was repeated 4 times per subject, each repetition using a different single pulse stimulation waveform: monophasic square, monophasic triangular,
monophasic quadratic and biphasic square. Results were retrieved from the averaging of the stimuli on each current intensity step. The square pulse needs less current intensity to generate the same response
amplitude regarding the other waves and presents a more steep curve slope and this effect is gradually decreasing for the triangular and quadratic pulse,respectively, being the difference even more evident regarding the biphasic pulse. The control of the waveform stimulation pulse allows varying the stimulusresponse curve slope.
32
Lo, Tun-Shin, e 羅敦信. "Efficacy of electrically evoked auditory brainstem response and electrically evoked compound action potential in programming children with the Nucleus-24 Cochlear Implants". Thesis, 2004. http://ndltd.ncl.edu.tw/handle/75360032289540431241.
Testo completoAbstract (sommario):
碩士國立台北護理學院
聽語障礙科學研究所
92
Several reports have shown the benefit in speech perception of cochlear implants. Determination of behavioral threshold levels (T-levels) and comfort levels (C-levels) of the cochlear implant users is very important for their performance of auditory perception. Either electrically evoked compound action potential (ECAP) or electrically evoked auditory brainstem response (EABR) has been studied to help with optimizing individual’s map parameters of cochlear implant users, particularly young children, in whom accurate behavioral T-levels and C-levels to electrical stimulation are difficult to obtain. The purpose of this study was to evaluate the efficacy of EABR and ECAP in programming children with Nucleus-24 cochlear implants by comparing their thresholds with behavioral T-levels and C-levels. Seventeen subjects (7 males and 10 females) with Nucleus 24 cochlear implant participated in this study. All subjects have received implantation at least for one year. Behavioral T-level and C-level were measured through the speech processor. Their auditory behavioral responses were reliable and stable MAPs were established. ECAP thresholds were recorded with the NRT 3.0v software (Cochlear, Australia). EABR thresholds were measured with evoked potential technique (Bravo, Nicolet, USA). SPSS 10.0 for Windows (SPSS Inc., Chicago, USA) was used for analysis. Regression models and paired t-tests were used to analyze the correlations between ECAP threshold, EABR threshold, behavioral T-level and C-level. ECAP thresholds were measured successfully in 64% of active electrodes measured, whereas EABR thresholds were measured in 71%. Unsuccessful recording of ECAP and EABR was observed mostly in subjects either with severe malformations or calcification of inner ear. Both ECAP and EABR could not be measured in four cases. When the subjects with severe malformations or calcification of inner ear were excluded, the rate of successful measurement raised to 94.2 % for EABR and 84.6 % for ECAP, respectively. EABR thresholds were on average 6.17 programming units (current levels) higher than ECAP thresholds. The correlation between EABR and ECAP thresholds was moderate (r = 0.755) and significant (p < 0.01). Paired t-tests revealed no significant difference between EABR and ECAP statistically (p = 0.051). The correlation between behavioral T-levels and ECAP thresholds or EABR thresholds was fair (r = 0.409 and 0.304, respectively). The correlation between behavioral C-levels and ECAP thresholds was moderate (r = 0.61), whereas the correlation between behavioral C-levels and EABR thresholds were fair (r = 0.283). The correlation between behavioral maps and EABR thresholds or ECAP thresholds is not strong. However, EABR and ECAP can be used as ancillary tools in programming MAP T-levels and C-levels of young children. In general, the rate of successful recording of EABR was higher than that of ECAP. Because recording of ECAP is easier and less time consuming than EABR, ECAP may be the choice of objective measurement. EABR measurement may be preferable for individuals whose ECAP can not be recorded successfully. Because of the very low rate of successful recording in young children either with severe malformations or calcification of inner ear, measurement of EABR and ECAP may not play a role in programming them.
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Syu, Ruei-Syuan, e 許睿軒. "The Design of CMOS Analog Front-End Acquisition Circuits for Electrocorticography (ECoG) and Evoked Compound Action Potential (ECAP) Recording in Implantable Medical Devices". Thesis, 2019. http://ndltd.ncl.edu.tw/handle/xd928n.
Testo completo
34
Kent, Alexander Rafael. "Characterization of Evoked Potentials During Deep Brain Stimulation in the Thalamus". Diss., 2013. http://hdl.handle.net/10161/8195.
Testo completoAbstract (sommario):
Deep brain stimulation (DBS) is an established surgical therapy for movement disorders. The mechanisms of action of DBS remain unclear, and selection of stimulation parameters is a clinical challenge and can result in sub-optimal outcomes. Closed-loop DBS systems would use a feedback control signal for automatic adjustment of DBS parameters and improved therapeutic effectiveness. We hypothesized that evoked compound action potentials (ECAPs), generated by activated neurons in the vicinity of the stimulating electrode, would reveal the type and spatial extent of neural activation, as well as provide signatures of clinical effectiveness. The objective of this dissertation was to record and characterize the ECAP during DBS to determine its suitability as a feedback signal in closed-loop systems. The ECAP was investigated using computer simulation and
First, we developed DBS-ECAP recording instrumentation to reduce the stimulus artifact and enable high fidelity measurements of the ECAP at short latency.
Second, we characterized ECAPs measured during thalamic DBS across stimulation parameters in anesthetized cats, and determined the neural origin of the ECAP using pharmacological interventions and a computer-based biophysical model of a thalamic network. This model simulated the ECAP response generated by a population of thalamic neurons, calculated ECAPs similar to experimental recordings, and indicated the relative contribution from different types of neural elements to the composite ECAP. Signal energy of the ECAP increased with DBS amplitude or pulse width, reflecting an increased extent of activation. Shorter latency, primary ECAP phases were generated by direct excitation of neural elements, whereas longer latency, secondary phases were generated by post-synaptic activation.
Third, intraoperative studies were conducted in human subjects with thalamic DBS for tremor, and the ECAP and tremor responses were measured across stimulation parameters. ECAP recording was technically challenging due to the presence of a wide range of stimulus artifact magnitudes across subjects, and an electrical circuit equivalent model and finite element method model both suggested that glial encapsulation around the DBS electrode increased the artifact size. Nevertheless, high fidelity ECAPs were recorded from acutely and chronically implanted DBS electrodes, and the energy of ECAP phases was correlated with changes in tremor.
Fourth, we used a computational model to understand how electrode design parameters influenced neural recording. Reducing the diameter or length of recording contacts increased the magnitude of single-unit responses, led to greater spatial sensitivity, and changed the relative contribution from local cells or passing axons. The effect of diameter or contact length varied across phases of population ECAPs, but ECAP signal energy increased with greater contact spacing, due to changes in the spatial sensitivity of the contacts. In addition, the signal increased with glial encapsulation in the peri-electrode space, decreased with local edema, and was unaffected by the physical presence of the highly conductive recording contacts.
It is feasible to record ECAP signals during DBS, and the correlation between ECAP characteristics and tremor suggests that this signal could be used in closed-loop DBS. This was demonstrated by implementation in simulation of a closed-loop system, in which a proportional-integral-derivative (PID) controller automatically adjusted DBS parameters to obtain a target ECAP energy value, and modified parameters in response to disturbances. The ECAP also provided insight into neural activation during DBS, with the dominant contribution to clinical ECAPs derived from excited cerebellothalamic fibers, suggesting that activation of these fibers is critical for DBS therapy.
Dissertation
35
(9178664), Maria I. Muzquiz, e Ivette M. Muzquiz (9178658). "Reversible Nerve Conduction Block Using Low Frequency Alternating Currents". Thesis, 2020.
Cerca il testo completoAbstract (sommario):
This thesis describes a novel method to reversibly and safely block nerve conduction using a low frequency alternating current (LFAC) waveform at 1 Hz applied through a bipolar extrafascicular electrode. This work follows up on observations made on excised mammalian peripheral nerves and earthworm nerve cords. An in-situ electrophysiology setup was used to assess the LFACwaveform on propagating action potentials (APs) within the cervical vagus nerve in anaesthetized Sprague-Dawley rats (n = 12). Two sets of bipolar cuff or hook electrodes were applied unilaterally to the cervical vagus nerve, which was crushed rostral to the electrodes to exclude reflex effects
on the animal. Pulse stimulation was applied to the rostral electrode, while the LFAC conditioning waveform was applied to the caudal electrode. The efferent volley, if unblocked, elicits acute bradycardia and hypotension. The degree of block of the vagal stimulation induced bradycardia
was used as a biomarker. Block was assessed by the ability to reduce the bradycardic drive by monitoring the heart rate (HR) and blood pressure (BP) during LFAC alone, LFAC with vagal stimulation, and vagal stimulation alone. LFAC applied via a hook electrode (n = 7) achieved 86.6 +/- 11% block at current levels 95 +/- 38 uAp (current to peak). When applied via a cuff electrode (n = 5) 85.3 +/- 4.60% block was achieved using current levels of 110 +/- 65 uAp. Furthermore, LFAC was explored on larger vagal afferent fibers in larger human sized nerve bundles projecting to effects mediated by a reflex. The effectiveness of LFAC was assessed in an in-situ electrophysiological setup on the left cervical vagus in anaesthetized domestic swine (n = 5). Two bipolar cuff electrodes were applied unilaterally to the cervical vagus nerve, which was crushed caudal to the electrodes to eliminate cardiac effects. A tripolar extrafascicular cuff electrode was placed most rostral on the nerve for recording of propagating APs induced by
electrical stimulation and blocked via the LFAC waveform.
Standard pulse stimulation was applied to the left cervical vagus to induce the Hering-Breuer reflex. If unblocked, the activation of the Hering-Breuer reflex would cause breathing to slow down and potentially cease. Block was quantified by the ability to reduce the effect of the Hering-Breuer
reflex by monitoring the breathing rate during LFAC alone, LFAC and vagal stimulation, and vagal stimulation alone. LFAC achieved 87.2 +/- 8.8% (n = 5) block at current levels of 0.8 +/- 0.3 mAp. Compound nerve action potentials (CNAP) were monitored directly. They show changes
in nerve activity during LFAC, which manifests itself as the slowing and amplitude reduction of components of the CNAPs. Since the waveform is balanced, all forward reactions are reversed, leading to a blocking method that is similar in nature to DC block without the potential issues of
toxic byproduct production. These results suggest that LFAC can achieve a high degree of nerve block in both small and large nerve bundles, resulting in the change in behavior of a biomarker, in-vivo in the mammalian nervous system at low amplitudes of electrical stimulation that are within the water window of the electrode.
36
Smit, Jacoba Elizabeth. "Modelled response of the electrically stimulated human auditory nerve fibre". Thesis, 2008. http://upetd.up.ac.za/thesis/available/etd-09182008-144232/.
Testo completo
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Martins, Pedro Freire de Sousa. "Biological evaluation of chlorogold complexes as potential anti-tumoural compounds: unraveling mechanisms of action". Master's thesis, 2014. http://hdl.handle.net/10362/14061.
Testo completoAbstract (sommario):
Cytotoxic chemotherapyat the present state is set asthe traditional hallmark of oncological treatment;however host toxicity and drug resistance acquisition remainas main challengesto overcome.Over the past few years there has been a great effort towards findingnew chemotherapeutic compounds with improvedpharmacodynamic and pharmacokinetic properties in order to achieve higher cancer specificityandreducedundesirable side effects. The present work intendedtocharacterize andelucidate the anti-tumouraleffect of chlorogold complexes bearing phosphineor N,O-donor ligands, and explorethe mechanisms by which they exert their antiproliferative propertiesas a part of this effort.Chloro(trimethylphosphine)gold(I)and Chloro(triphenylphosphine)gold(I)in vitrocell viability assays in A549 tumour cell line exhibited IC50valuesof 44.4 and 30.0μMrespectively, plus3.3 and, 5.4 μMin H1975 respectively.Predisposition of the chlorogold complexesto targetnon-tumoural cells,evaluated in fibroblastsnormal cell line,revealed an IC50value of 7.7 and 19.1μMrespectively.Apoptosismorphological featureswerealso confirmed. A549 and H1975 cell line exposure to both chlorogold complexes at their respective IC50values, revealed nuclear fragmentation and chromatin condensation, observed by Hoechst 33258 staining. These results were furtherprovenforby flow cytometry analysis. Double staining with Annexin V-FITC and PropidiumIodide in A549after compound exposurerevealed the ability to induce mechanisms of cell death by apoptosis in a dose-dependent fashion. Chloro(triphenylphosphine)gold(I) was further proven to be able to induce cell cycle delay, this effect being especially evident for S-phase. Moreovercompound interaction with the DNA molecule was proven to be either weak or inexistent through electrophoretic mobility assayrevealedbythe compounds’ inability to compromise plasmidDNA conformation. Proteomic studieseven though not conclusive regarding chlorogold compounds’ mechanism of action,allowed the identification of new potential biomarkers for prediction of prognosisin non-small-cell lung carcinoma.
38
Hsiu-Lien, Cheng, e 鄭秀蓮. "The comparison of cochlear traveling time in Meniere’s disease and normal hearing ears using derived-band cochlear compound action potentials and auditory brainstem responses". Thesis, 2007. http://ndltd.ncl.edu.tw/handle/44926540443587003516.
Testo completoAbstract (sommario):
碩士國立台北護理學院
聽語障礙科學研究所
96
Background: This study is designed for comparing the cochlear traveling time difference between ears of Meniere’s disease (MD) patients and normal subjects. Both derived-band auditory brainstem responses (ABRs) and compound action potentials (CAPs) detecting techniques were used. To improve the recognized waveform latencies, the CAP was detected by using the Biologic TM-EcochGtrode system electrodes. Derived-band technique was adopted and modified from previous literature by applying an ipsilateral high-pass masking noise. Material and Methods: This study received institutional review board approval. Twenty-two unilateral Meniere’s disease patients (8 males, 14 females) diagnosed according to the 1995 guidelines published by American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS, 1995) were included with the symptom presented within one week, aged 26 to 60 years, and thirty ears from thirty subjects with hearing sensitivity within normal limits (15 left, 15 right), aged 20 to 43 years. All subjects underwent extratympanic electrode insertion using the Biologic TM-ECochGtrode system (Biologic Systems Corp, Mundelein,Ill) and ABR responses to six stimulus conditions were obtained, including click alone and click presented with various ipsilateral pink noise high-pass filtered maskers (cut-off frequencies were close to 8000, 4000, 2000, 1000 and 500 Hz). Six auditory brainstem evoked potentials are recorded and subtracted by each other, resulting in above 8000 Hz, 8000-4000 Hz, 4000-2000 Hz, 2000-1000 Hz and 1000-500 Hz five derived-band ABRs. Estimates from derived-band ABRs and CAP were comparable to each other. Results: More than 85 % for both derived-band CAP and wave V latencies can be identified in a low-frequency band (500-1000 Hz). The percentage of recognizable latency presented in derived-band CAP (93.4 %) is higher than the one in ABR wave V (89.0 %) across all frequencies. Both peak latencies presented in derived-band CAP and ABR wave V increase as the cochlea is masked from 8 kHz and higher down to 0.5 kHz. The absolute band-derived latency distribution presented in MD group overlaps the one in normal hearing group either observed in CAP or wave V. The latency difference between click alone and band-derived ABR detected both in CAP and wave V, also revealed no significant difference compared between experimental and normal groups. However, the latency change between click alone and band-derived ABR evaluated in both CAP and wave V, significant increase in MD group when compared with normal hearing group at low frequency band (500-1000 Hz) (P< 0.05). Conclusion: 1. Recognizable latencies presented in derived-band CAP are improved by tympanic membrane electrodes recording. 2. With this modified derived-band CAP recording, the identification ratio of cochlear traveling wave velocity in CAP is higher than the one in ABR wave V. 3. By comparing the absolute peak latency values at each band-derived frequency between MD group and control group, there is no significant difference. This result may be referred to the variation of disease progression in collected MD patients in this study. 4. Both band-derived CAP and ABR wave V can detect the alteration of the cochlear traveling wave velocity in a low frequency band of 500-1000 Hz when compared using latency change in MD group. This result suggests that the derived-band technique may be more sensitive in detecting an endolymphatic hydrop condition in an assumed low frequency map in the cochlea.
39
(9356939), Jui-wei Tsai. "Digital Signal Processing Architecture Design for Closed-Loop Electrical Nerve Stimulation Systems". Thesis, 2020.
Cerca il testo completoAbstract (sommario):
Electrical nerve stimulation (ENS) is an emerging therapy for many neurological disorders. Compared with conventional one-way stimulations, closed-loop ENS approaches increase the stimulation efficacy and minimize patient's discomfort by constantly adjusting the stimulation parameters according to the feedback biomarkers from patients. Wireless neurostimulation devices capable of both stimulation and telemetry of recorded physiological signals are welcome for closed-loop ENS systems to improve the quality and reduce the costs of treatments, and real-time digital signal processing (DSP) engines processing and extracting features from recorded signals can reduce the data transmission rate and the resulting power consumption of wireless devices. Electrically-evoked compound action potential (ECAP) is an objective measure of nerve activity and has been used as the feedback biomarker in closed-loop ENS systems including neural response telemetry (NRT) systems and a newly proposed autonomous nerve control (ANC) platform. It's desirable to design a DSP engine for real-time processing of ECAP in closed-loop ENS systems.
This thesis focuses on developing the DSP architecture for real-time processing of ECAP, including stimulus artifact rejection (SAR), denoising, and extraction of nerve fiber responses as biomedical features, and its VLSI implementation for optimal hardware costs. The first part presents the DSP architecture for real-time SAR and denoising of ECAP in NRT systems. A bidirectional-filtered coherent averaging (BFCA) method is proposed, which enables the configurable linear-phase filter to be realized hardware efficiently for distortion-free filtering of ECAPs and can be easily combined with the alternating-polarity (AP) stimulation method for SAR. Design techniques including folded-IIR filter and division-free averaging are incorporated to reduce the computation cost. The second part presents the fiber-response extraction engine (FREE), a dedicated DSP engine for nerve activation control in the ANC platform. FREE employs the DSP architecture of the BFCA method combined with the AP stimulation, and the architecture of computationally efficient peak detection and classification algorithms for fiber response extraction from ECAP. FREE is mapped onto a custom-made and battery-powered wearable wireless device incorporating a low-power FPGA, a Bluetooth transceiver, a stimulation and recording analog front-end and a power-management unit. In comparison with previous software-based signal processing, FREE not only reduces the data rate of wireless devices but also improves the precision of fiber response classification in noisy environments, which contributes to the construction of high-accuracy nerve activation profile in the ANC platform. An application-specific integrated circuit (ASIC) version of FREE is implemented in 180-nm CMOS technology, with total chip area and core power consumption of 19.98 mm2 and 1.95 mW, respectively.
40
Effertz, Thomas. "Candidate mechanosensitive transduction channels in Drosophila melanogaster". Doctoral thesis, 2011. http://hdl.handle.net/11858/00-1735-0000-0006-AE0E-8.
Testo completo