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Sasaki, Tatsuya, Kyouichi Suzuki, Masato Matsumoto, Taku Sato, Namio Kodama et Keiko Yago. « Origin of surface potentials evoked by electrical stimulation of oculomotor nerves : are they related to electrooculographic or electromyographic events ? » Journal of Neurosurgery 97, no 4 (octobre 2002) : 941–44. http://dx.doi.org/10.3171/jns.2002.97.4.0941.
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Object. Evoked potentials elicited by electrical stimulation of the oculomotor nerve and recorded from surface electrodes placed on the skin around the eyeball reportedly originate in the eye and are represented on electrooculograms. Because evoked potentials recorded from surface electrodes are extremely similar to those of extraocular muscles, which are represented on electromyograms, the authors investigated the true origin of these potentials. Methods. Evoked potentials elicited by electrical stimulation of the canine oculomotor nerve were recorded from surface electrodes placed on the skin around the eyeball. A thread sutured to the center of the cornea was pulled and the potentials that were evoked during the resultant eye movement were recorded. These potentials were confirmed to originate in the eye and to be represented on electrooculograms because their waveforms were unaffected by the administration of muscle relaxant. To eliminate the influence of this source, the retina, a main origin of standing potentials of the eyeball, was removed. This resulted in the disappearance of electrooculography (EOG) waves elicited by eye movement. Surface potentials elicited by oculomotor nerve stimulation were the same before and after removal of the retina. Again the oculomotor nerve was electrically stimulated and electromyography (EMG) response of the extraocular muscles was recorded at the same time that potentials were recorded from the surface electrodes. In their peak latencies, amplitudes, and waveforms, the evoked potentials obtained from surface electrodes were almost identical to EMG responses of extraocular muscles. Conclusions. Evoked potentials elicited by electrical stimulation of the oculomotor nerves and obtained from surface electrodes originated from EMG responses of extraocular muscles. These evoked potentials do not derive from the eye.
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Schwindt, Peter C., et Wayne E. Crill. « Synaptically Evoked Dendritic Action Potentials in Rat Neocortical Pyramidal Neurons ». Journal of Neurophysiology 79, no 5 (1 mai 1998) : 2432–46. http://dx.doi.org/10.1152/jn.1998.79.5.2432.
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Schwindt, Peter C. and Wayne E. Crill. Synaptically evoked dendritic action potentials in rat neocortical pyramidal neurons. J. Neurophysiol. 79: 2432–2446, 1998. In a previous study iontophoresis of glutamate on the apical dendrite of layer 5 pyramidal neurons from rat neocortex was used to identify sites at which dendritic depolarization evoked small, prolonged Ca2+ spikes and/or low-threshold Na+ spikes recorded by an intracellular microelectrode in the soma. These spikes were identified as originating in the dendrite. Here we evoke similar dendritic responses by electrical stimulation of presynaptic elements near the tip of the iontophoretic electrode with the use of a second extracellular electrode. In 9 of 12 recorded cells, electrically evoked excitatory postsynaptic potentials (EPSPs) above a minimum size triggered all-or-none postsynaptic responses similar to those evoked by dendritic glutamate iontophoresis at the same site. Both the synaptically evoked and the iontophoretically evoked depolarizations were abolished reversably by blockade of glutamate receptors. In all recorded cells, the combination of iontophoresis and an EPSP, each of which was subthreshold for the dendritic spike when given alone, evoked a dendritic spike similar to that evoked by a sufficiently large iontophoresis. In one cell tested, dendritic spikes could be evoked by the summation of two independent subthreshold EPSPs evoked by stimulation at two different locations. We conclude that the dendritic spikes are not unique to the use of glutamate iontophoresis because similar spikes can be evoked by EPSPs. We discuss the implications of these results for synaptic integration and for the interpretation of recorded synaptic potentials.
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Perrier, Jean-François, Boris Lamotte D'Incamps, Nezha Kouchtir-Devanne, Léna Jami et Daniel Zytnicki. « Effects on Peroneal Motoneurons of Cutaneous Afferents Activated by Mechanical or Electrical Stimulations ». Journal of Neurophysiology 83, no 6 (1 juin 2000) : 3209–16. http://dx.doi.org/10.1152/jn.2000.83.6.3209.
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The postsynaptic potentials elicited in peroneal motoneurons by either mechanical stimulation of cutaneous areas innervated by the superficial peroneal nerve (SP) or repetitive electrical stimulation of SP were compared in anesthetized cats. After denervation of the foot sparing only the territory of SP terminal branches, reproducible mechanical stimulations were applied by pressure on the plantar surface of the toes via a plastic disk attached to a servo-length device, causing a mild compression of toes. This stimulus evoked small but consistent postsynaptic potentials in every peroneal motoneuron. Weak stimuli elicited only excitatory postsynaptic potentials (EPSPs), whereas increase in stimulation strength allowed distinction of three patterns of response. In about one half of the sample, mechanical stimulation or trains of 20/s electric pulses at strengths up to six times the threshold of the most excitable fibers in the nerve evoked only EPSPs. Responses to electrical stimulation appeared with 3–7 ms central latencies, suggesting oligosynaptic pathways. In another, smaller fraction of the sample, inhibitory postsynaptic potentials (IPSPs) appeared with an increase of stimulation strength, and the last fraction showed a mixed pattern of excitation and inhibition. In 24 of 32 motoneurons where electrical and mechanical effects could be compared, the responses were similar, and in 6 others, they changed from pure excitation on mechanical stimulation to mixed on electrical stimulation. With both kinds of stimulation, stronger stimulations were required to evoke inhibitory postsynaptic potentials (IPSPs), which appeared at longer central latencies than EPSPs, indicating longer interneuronal pathways. The similarity of responses to mechanical and electrical stimulation in a majority of peroneal motoneurons suggests that the effects of commonly used electrical stimulation are good predictors of the responses of peroneal motoneurons to natural skin stimulation. The different types of responses to cutaneous afferents from SP territory reflect a complex connectivity allowing modulations of cutaneous reflex responses in various postures and gaits.
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Oberle, Joachim, Gregor Antoniadis, Erich Kast et Hans-Peter Richter. « Evaluation of Traumatic Cervical Nerve Root Injuries by Intraoperative Evoked Potentials ». Neurosurgery 51, no 5 (1 novembre 2002) : 1182–90. http://dx.doi.org/10.1097/00006123-200211000-00012.
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Abstract OBJECTIVE To evaluate intraoperative evoked potentials as a diagnostic tool in traumatic brachial plexus injuries. METHODS Thirteen patients with traumatic brachial plexus injuries were investigated by intradural nerve root inspection (n = 28 roots) via cervical hemilaminectomy to assess or rule out nerve root avulsion from the spinal cord. Two to 8 weeks later, evoked potentials from neck and scalp were recorded after direct electrical nerve root stimulation close to the vertebral foramen during operative brachial plexus repair via an anterior (supraclavicular and infraclavicular) approach. Recordings were performed without and after full muscle relaxation. RESULTS There was a clear relationship between the state of the root as documented by intradural root inspection and the result of intraoperative recording of evoked potentials: the absence of evoked muscle action potentials from neck muscles demonstrated a 100% sensitivity for anterior root lesions, whereas sensory evoked potentials from the scalp demonstrated a 100% sensitivity for posterior root lesions. Moreover, roots could be identified with preserved continuity that did not conduct, suggesting a nerve lesion in continuity. CONCLUSION Intraoperative evoked muscle action potentials and sensory evoked potentials after electrical nerve root stimulation allow selective functional evaluation of anterior and posterior nerve roots in patients with traumatic brachial plexus injuries. The high sensitivity and reliability of this test obviate the need for additional diagnostic surgery.
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Zhang, Jianmei, Victor Z. Han, Johannes Meek et Curtis C. Bell. « Granular Cells of the Mormyrid Electrosensory Lobe and Postsynaptic Control Over Presynaptic Spike Occurrence and Amplitude Through an Electrical Synapse ». Journal of Neurophysiology 97, no 3 (mars 2007) : 2191–203. http://dx.doi.org/10.1152/jn.01262.2006.
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Primary afferent fibers from the electroreceptors of mormyrid electric fish use a latency code to signal the intensity of electrical current evoked by the fish's own electric organ discharge (EOD). The afferent fibers terminate centrally in the deep and superficial granular layers of the electrosensory lobe with morphologically mixed chemical–electrical synapses. The granular cells in these layers seem to decode afferent latency through an interaction between primary afferent input and a corollary discharge input associated with the EOD motor command. We studied the physiology of deep and superficial granular cells in a slice preparation with whole cell patch recording and electrical stimulation of afferent fibers. Afferent stimulation evoked large all-or-none electrical excitatory postsynaptic potentials (EPSPs) and large all or none GABAergic inhibitory postsynaptic potentials (IPSPs) in both superficial and deep granular cells. The amplitudes of the electrical EPSPs depended on postsynaptic membrane potential, with maximum amplitudes at membrane potentials between −65 and −110 mV. Hyperpolarization beyond this level resulted in either the abrupt disappearance of EPSPs, a step-like reduction to a smaller EPSP, or a graded reduction in EPSP amplitude. Depolarization to membrane potentials lower than that yielding a maximum caused a linear decrease in EPSP amplitude, with EPSP amplitude reaching 0 mV at potentials between −55 and −40 mV. We suggest that the dependence of EPSP size on postsynaptic membrane potential is caused by close linkage of pre- and postsynaptic membrane potentials through a high-conductance gap junction. We also suggest that this dependence may result in functionally important nonlinear interactions between synaptic inputs.
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Wang, Guo-Du, Xi-Yu Wang, Sumei Liu, Yun Xia, Fei Zou, Meihua Qu, Bradley J. Needleman, Dean J. Mikami et Jackie D. Wood. « β-Nicotinamide adenine dinucleotide acts at prejunctional adenosine A1 receptors to suppress inhibitory musculomotor neurotransmission in guinea pig colon and human jejunum ». American Journal of Physiology-Gastrointestinal and Liver Physiology 308, no 11 (1 juin 2015) : G955—G963. http://dx.doi.org/10.1152/ajpgi.00430.2014.
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Intracellular microelectrodes were used to record neurogenic inhibitory junction potentials in the intestinal circular muscle coat. Electrical field stimulation was used to stimulate intramural neurons and evoke contraction of the smooth musculature. Exposure to β-nicotinamide adenine dinucleotide (β-NAD) did not alter smooth muscle membrane potential in guinea pig colon or human jejunum. ATP, ADP, β-NAD, and adenosine, as well as the purinergic P2Y1 receptor antagonists MRS 2179 and MRS 2500 and the adenosine A1 receptor agonist 2-chloro- N6-cyclopentyladenosine, each suppressed inhibitory junction potentials in guinea pig and human preparations. β-NAD suppressed contractile force of twitch-like contractions evoked by electrical field stimulation in guinea pig and human preparations. P2Y1 receptor antagonists did not reverse this action. Stimulation of adenosine A1 receptors with 2-chloro- N6-cyclopentyladenosine suppressed the force of twitch contractions evoked by electrical field stimulation in like manner to the action of β-NAD. Blockade of adenosine A1 receptors with 8-cyclopentyl-1,3-dipropylxanthine suppressed the inhibitory action of β-NAD on the force of electrically evoked contractions. The results do not support an inhibitory neurotransmitter role for β-NAD at intestinal neuromuscular junctions. The data suggest that β-NAD is a ligand for the adenosine A1 receptor subtype expressed by neurons in the enteric nervous system. The influence of β-NAD on intestinal motility emerges from adenosine A1 receptor-mediated suppression of neurotransmitter release at inhibitory neuromuscular junctions.
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Sato, Masanori, Namio Kodama, Tatsuya Sasaki et Mamoru Ohta. « Olfactory evoked potentials : experimental and clinical studies ». Journal of Neurosurgery 85, no 6 (décembre 1996) : 1122–26. http://dx.doi.org/10.3171/jns.1996.85.6.1122.
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✓ Olfactory evoked potentials (OEPs), obtained by electrical stimulation of the olfactory mucosa, were recorded in dogs and humans to develop an objective method for evaluating olfactory functions. In dogs, OEPs were recorded from the olfactory tract and the scalp. The latency of the first negative peak was approximately 40 msec. A response was not obtained after stimulation of the nasal mucosa and disappeared after sectioning of the olfactory nerve. With increasing frequencies of repetitive stimulation, the amplitude was reduced, suggesting that the response was synaptically mediated. These results demonstrate that evoked potentials from the olfactory tract and the scalp following electrical stimulation of the olfactory mucosa originate specifically from the olfactory system. In humans, a stimulating electrode with a soft catheter was fixed on the olfactory mucosa. The OEPs from the olfactory tract, recorded with a negative peak of approximately 27 msec, had similar characteristics to OEPs found in dogs. The OEPs from the olfactory tract in humans also originate specifically from the olfactory system. The authors postulate that OEPs obtained by electrical stimulation of the olfactory mucosa may prove useful for intraoperative monitoring of olfactory functions.
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KIKUCHI, Yasuhiro, Tatsuya SASAKI, Masato MATSUMOTO, Tomoyoshi OIKAWA, Takeshi ITAKURA et Namio KODAMA. « Optic Nerve Evoked Potentials Elicited by Electrical Stimulation ». Neurologia medico-chirurgica 45, no 7 (2005) : 349–55. http://dx.doi.org/10.2176/nmc.45.349.
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Yu, Dong-Zhen, et Shan-Kai Yin. « R035 : Electrical-Evoked Field Potentials within Vestibular Nuclei ». Otolaryngology–Head and Neck Surgery 135, no 2_suppl (août 2006) : P116. http://dx.doi.org/10.1016/j.otohns.2006.06.787.
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Dorfman, L. J., M. Gaynon, J. Ceranski, A. A. Louis et J. E. Howard. « Visual electrical evoked potentials : Evaluation of ocular injuries ». Neurology 37, no 1 (1 janvier 1987) : 123. http://dx.doi.org/10.1212/wnl.37.1.123.
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Madsen, Caspar Skau, Nanna Brix Finnerup et Ulf Baumgärtner. « Assessment of small fibers using evoked potentials ». Scandinavian Journal of Pain 5, no 2 (1 avril 2014) : 111–18. http://dx.doi.org/10.1016/j.sjpain.2013.11.007.
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AbstractBackground and purposeConventional neurophysiological techniques do not assess the function of nociceptive pathways and are inadequate to detect abnormalities in patients with small-fiber damage. This overview aims to give an update on the methods and techniques used to assess small fiber (Aδ- and C-fibers) function using evoked potentials in research and clinical settings.MethodsNoxious radiant or contact heat allows the recording of heat-evoked brain potentials commonly referred to as laser evoked potentials (LEPs) and contact heat-evoked potentials (CHEPs). Both methods reliably assess the loss of Aδ-fiber function by means of reduced amplitude and increased latency of late responses, whereas other methods have been developed to record ultra-late C-fiber-related potentials. Methodological considerations with the use of LEPs and CHEPs include fixed versus variable stimulation site, application pressure, and attentional factors. While the amplitude of LEPs and CHEPs often correlates with the reported intensity of the stimulation, these factors may also be dissociated. It is suggested that the magnitude of the response may be related to the saliency of the noxious stimulus (the ability of the stimulus to stand out from the background) rather than the pain perception.ResultsLEPs and CHEPs are increasingly used as objective laboratory tests to assess the pathways mediating thermal pain, but new methods have recently been developed to evaluate other small-fiber pathways. Pain-related electrically evoked potentials with a low-intensity electrical simulation have been proposed as an alternative method to selectively activate Aδ-nociceptors. A new technique using a flat tip mechanical stimulator has been shown to elicit brain potentials following activation of Type I A mechano-heat (AMH) fibers. These pinprick-evoked potentials (PEP) have a morphology resembling those of heat-evoked potentials following activation of Type II AMH fibers, but with a shorter latency. Cool-evoked potentials can be used for recording the non-nociceptive pathways for cooling. At present, the use of cool-evoked potentials is still in the experimental state. Contact thermodes designed to generate steep heat ramps may be programmed differently to generate cool ramps from a baseline of 35◦C down to 32◦C or 30◦C. Small-fiber evoked potentials are valuable tools for assessment of small-fiber function in sensory neuropathy, central nervous system lesion, and for the diagnosis of neuropathic pain. Recent studies suggest that both CHEPs and pinprick-evoked potentials may also be convenient tools to assess sensitization of the nociceptive system.ConclusionsIn future studies, small-fiber evoked potentials may also be used in studies that aim to understand pain mechanisms including different neuropathic pain phenotypes, such as cold- or touch-evoked allodynia, and to identify predictors of response to pharmacological pain treatment.ImplicationsFuture studies are needed for some of the newly developed methods.
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Linster, Christiane, Bradley P. Wyble et Michael E. Hasselmo. « Electrical Stimulation of the Horizontal Limb of the Diagonal Band of Broca Modulates Population EPSPs in Piriform Cortex ». Journal of Neurophysiology 81, no 6 (1 juin 1999) : 2737–42. http://dx.doi.org/10.1152/jn.1999.81.6.2737.
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Electrical stimulation of the horizontal limb of the diagonal band of Broca modulates population EPSPs in piriform cortex. Electrical stimulation of the horizontal limb of the diagonal band of Broca (HDB) was coupled with recording of evoked potentials in the piriform cortex. Stimulation of the HDB caused an enhancement of the late, disynaptic component of the evoked potential elicited by stimulation of the lateral olfactory tract but caused a suppression of the synaptic potential elicited by stimulation of the posterior piriform cortex. The muscarinic antagonist scopolamine blocked both effects of HDB stimulation. The enhancement of disynaptic potentials could be due to cholinergic depolarization of pyramidal cells, whereas the suppression of potentials evoked by posterior piriform stimulation could be due to presynaptic inhibition of intrinsic fiber synaptic transmission by acetylcholine.
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Hutzler, M., A. Lambacher, B. Eversmann, M. Jenkner, R. Thewes et P. Fromherz. « High-Resolution Multitransistor Array Recording of Electrical Field Potentials in Cultured Brain Slices ». Journal of Neurophysiology 96, no 3 (septembre 2006) : 1638–45. http://dx.doi.org/10.1152/jn.00347.2006.
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We report on the recording of electrical activity in cultured hippocampal slices by a multitransistor array (MTA) with 16,384 elements. Time-resolved imaging is achieved with a resolution of 7.8 μm on an area of 1 mm2 at 2 kHz. A read-out of fewer elements allows an enhanced time resolution. Individual transistor signals are caused by local evoked field potentials. They agree with micropipette measurements in amplitude and shape. The spatial continuity of the records provides time-resolved images of evoked field potentials and allows the detection of functional correlations over large distances. As examples, fast propagating waves of presynaptic action potentials are recorded as well as patterns of excitatory postsynaptic potentials across and along cornu ammonis.
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Greenspan, J. D., S. Ohara, P. Franaszczuk, D. S. Veldhuijzen et F. A. Lenz. « Cold Stimuli Evoke Potentials That Can Be Recorded Directly From Parasylvian Cortex in Humans ». Journal of Neurophysiology 100, no 4 (octobre 2008) : 2282–86. http://dx.doi.org/10.1152/jn.90564.2008.
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Anatomic, imaging, and lesion studies suggest that insular or parietal opercular cortical structures mediate the sensation of nonpainful cold. We have now tested the hypothesis that cold stimuli evoke electrical responses from these cortical structures in humans. We recorded the response to cold stimuli from electrodes implanted directly over parasylvian cortex for the investigation of intractable seizures. The results demonstrate that slow potentials can be evoked consistently over structures adjacent to the sylvian fissure in response to nonpainful cold. The polarity of these cold evoked potentials (EPs) for electrodes above the sylvian fissure is opposite to those below. These results suggest that the generator of cold EPs is close to the sylvian fissure in the parietal operculum or insula.
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Chey, W. D., A. Beydoun, D. J. Roberts, W. L. Hasler et C. Owyang. « Octreotide reduces perception of rectal electrical stimulation by spinal afferent pathway inhibition ». American Journal of Physiology-Gastrointestinal and Liver Physiology 269, no 6 (1 décembre 1995) : G821—G826. http://dx.doi.org/10.1152/ajpgi.1995.269.6.g821.
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Octreotide reduces perception of rectal distension in normal volunteers and irritable bowel patients. To localize octreotide's site of action, perceptual and evoked potential responses to rectal electrical stimulation were tested in seven normal volunteers after double-blind octreotide (100 micrograms 2) or placebo. After octreotide, the currents needed to elicit threshold perception of square-wave impulses delivered to the rectum were 29% higher than after placebo. When electrical stimulation was delivered at constant currents 50% above threshold, rectal perception scores were significantly reduced after octreotide compared with placebo. Rectal electrical stimulation led to characteristic and reproducible cerebral evoked potentials. Octreotide had no effect on latencies, but reduced peak-to-peak amplitudes by 35% compared with placebo. Rectal electrical stimulation also led to characteristic and reproducible spinal evoked potentials. Octreotide had no effect on spinal latencies, but reduced peak-to-peak amplitudes by 51%. In conclusion, octreotide reduces perception of rectal electrical stimulation, which is associated with inhibition of cerebral and spinal evoked potential amplitude, indicating effects on spinal afferent pathways.
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Purdy, Suzanne C., et Kirsty Gardner-Berry. « Auditory Evoked Potentials and Cochlear Implants : Research Findings and Clinical Applications in Children ». Perspectives on Hearing and Hearing Disorders in Childhood 19, no 1 (mars 2009) : 14–21. http://dx.doi.org/10.1044/hhdc19.1.14.
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Abstract Auditory evoked potentials can be used to objectively assess hearing sensitivity, central auditory processing, and neural encoding of speech sounds up to the level of the auditory cortex. Evoked potentials have been of interest to clinicians and researchers in the cochlear implant field for a long time because of their potential for objectively predicting cochlear implant outcomes, as well as improving candidacy determination, and implant programming. Neural response telemetry and intra-operative electrical auditory brainstem recording have been routinely performed by implant programs for many years. Recently, there has been great interest in potential clinical applications of cortical auditory evoked potentials in the implant field. Research and clinical applications are reviewed and case studies are presented that illustrate clinical applications of cortical evoked potentials in children before and after implantation.
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Kondo, T., K. Tamura, K. Onoe, H. Takahira, Y. Ohta et H. Yamabayashi. « In vivo recording of electrical activity of canine tracheal smooth muscle ». Journal of Applied Physiology 72, no 1 (1 janvier 1992) : 135–42. http://dx.doi.org/10.1152/jappl.1992.72.1.135.
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Electrical activity of the tracheal smooth muscle was studied using extracellular bipolar electrodes in 37 decerebrate, paralyzed, and mechanically ventilated dogs. A spontaneous oscillatory potential that consisted of a slow sinusoidal wave of 0.57 +/- 0.13 (SD) Hz mean frequency but lacked a fast spike component was recorded from 15 dogs. Lung collapse accomplished by bilateral pneumothoraxes evoked or augmented the slow potentials that were associated with an increase in tracheal muscle contraction in 26 dogs. This suggests that the inputs from the airway mechanoreceptors reflexly activate the tracheal smooth muscle cells. Bilateral vagal transection abolished both the spontaneous and the reflexly evoked slow waves and provided relaxation of the tracheal smooth muscle. Electrical stimulation of the distal nerve with a train pulse (0.5 ms, 1–30 Hz) evoked slow-wave oscillatory potentials accompanied by a contraction of the tracheal smooth muscle in all the experimental animals. Our observations in this in vivo study confirm that the electrical activity of tracheal smooth muscle consists of slow oscillatory potentials and that tracheal contraction is at least partly coupled to the slow-wave activity of the smooth muscle.
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Feng, Z. C., T. J. Sick et M. Rosenthal. « Extracellular pH and suppression of electrical activity during anoxia in turtle and rat brain ». American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 258, no 1 (1 janvier 1990) : R205—R210. http://dx.doi.org/10.1152/ajpregu.1990.258.1.r205.
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To evaluate the contribution of extracellular H+ activity toward depression of brain electrical activity during anoxia, extracellular pH (pHe) and field potentials were measured in turtle and rat olfactory bulbs with ion-selective microelectrodes. This study tests the hypothesis that unique regulation of pHe contributes to the remarkable tolerance of turtle brain to prolonged anoxia. Hypercapnea (20% CO2 ventilation) depressed olfactory bulb evoked potentials 25-30% in both rat and turtle. During anoxia, evoked potentials were completely abolished within 1 min in rat olfactory bulb but decreased to only 40% of control after 4 h in the turtle despite similar changes in brain pHe. Anoxia-induced acidification of turtle brain was exacerbated by hypercapnea and was attenuated by hypocapnea or by hypocapnea plus intravenous infusion of sodium bicarbonate. However, these manipulations of pHe during anoxia in turtle brain had little effect on depression of evoked potentials. We conclude that energy failure, rather than extracellular acidification, is the major contributor toward suppression of electrical activity in mammalian brain and that preservation of energy balance, rather than unique pH regulation, is responsible for protection of turtle brain during anoxia.
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Macdonald, Kurt D., Eva Fifkova, Michael S. Jones et Daniel S. Barth. « Focal Stimulation of the Thalamic Reticular Nucleus Induces Focal Gamma Waves in Cortex ». Journal of Neurophysiology 79, no 1 (1 janvier 1998) : 474–77. http://dx.doi.org/10.1152/jn.1998.79.1.474.
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MacDonald, Kurt D., Eva Fifkova, Michael S. Jones, and Daniel S. Barth. Focal stimulation of the thalamic reticular nucleus induces focal gamma waves in cortex. J. Neurophysiol. 79: 474–477, 1998. Electrical stimulation of the thalamic reticular nucleus (TRN; 0.5-s trains of 500-Hz 0.5-ms pulses at 5–10 μA) evokes focal oscillations of cortical electrical potentials in the gamma frequency band (∼35–55 Hz). These evoked oscillations are specific to either the somatosensory or auditory cortex and to subregions of the cortical receptotopic map, depending on what part of the TRN is stimulated. Focal stimulation of the internal capsule, however, evokes focal slow potentials, without gamma activity. Our results suggest that the TRN's role extends beyond that of general cortical arousal to include specific modality and submodality activation of the forebrain.
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Wilson, Donald A. « Synaptic Correlates of Odor Habituation in the Rat Anterior Piriform Cortex ». Journal of Neurophysiology 80, no 2 (1 août 1998) : 998–1001. http://dx.doi.org/10.1152/jn.1998.80.2.998.
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Wilson, Donald A. Synaptic correlates of odor habituation in the rat anterior piriform cortex. J. Neurophysiol. 80: 998–1001, 1998. Responses of anterior piriform cortex layer II/III neurons to both odors and electrical stimulation of the lateral olfactory tract (LOT) were measured with intracellular recordings in urethan-anesthetized, freely breathing rats. Odor-evoked, respiration-entrained postsynaptic potentials (PSPs) rapidly habituated during a 50-s odor stimulus, then spontaneously recovered within 2 min of odor termination. Associated with the decrease in odor-evoked PSP amplitude was a decrease in the monosynaptic excitatory postsynaptic potentials (EPSPs) evoked by electrical stimulation of the LOT. The decrement in LOT-evoked EPSPs recovered with a time course similar to the odor response recovery. These results demonstrate that odor habituation is associated with a decrease in afferent synaptic efficacy in the anterior piriform cortex.
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Selskii, Anton, Maksim Zhuravlev, Anastasiia Runnova, Elena Grinina, Marina Konovalova et Rail Shamionov. « A study of changes in cognitive evoked potentials in persons with visual impairment ». E3S Web of Conferences 273 (2021) : 10051. http://dx.doi.org/10.1051/e3sconf/202127310051.
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In this work we have used psychophysiological assessments of the human brain electrical activity according to the classical neurological method for calculating the evoked potential. The experiment was designed to extraction cognitive evoked potentials. Taking into account the characteristic components, the temporal dynamics of the EEG data channels was investigated. This approach allows one to consistently assess the distribution of all components of the evoked potential on the subject's head map. Based on the results of evoked potentials processing, a statistical comparison of the components of evoked potentials in subjects of different groups by channels was carried out in accordance with the Wilcoxon test. Demonstrated for which channels the results significantly differ between the two groups of subjects. The sequence of evoked potential analysis demonstrated in the article suits for adjusting the settings of the “brain-computer” systems for a particular subject and allows to select channels used in further BCI training efficiently.
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Matamala, J. M., J. L. Castillo, R. Verdugo, M. Campero, G. Barraza, Y. T. Wang et R. J. Guiloff. « P131 : Evoked potentials after painful electrical stimulation : preliminary results ». Clinical Neurophysiology 125 (juin 2014) : S83. http://dx.doi.org/10.1016/s1388-2457(14)50276-3.
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Benchabane, Besma, Moncef Benkherrat et Salah Djelel. « Statistical Method to Extract Evoked Potentials from Noise ». E3S Web of Conferences 170 (2020) : 02005. http://dx.doi.org/10.1051/e3sconf/202017002005.
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Evoked Potentials are induced by visual or auditory stimulation. The Evoked Potentials represent transient electrical activities of some limited brain regions. The signal-noise ratio (SNR) of the EPs is typically around -10 dB. In order to study brain activities related to information processing in the brain, one has to “extract” the single EPs from the noise. We propose a method does not require a priori information concerning the characteristics (time, frequency) of the signal and does not use a template. The method proposed in this work use the wavelet transform associated with a statistical test.
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Graf, Rudolf, Kazuo Kataoka, Gerd Rosner et Wolf-Dieter Heiss. « Cortical Deafferentation in Cat Focal Ischemia : Disturbance and Recovery of Sensory Functions in Cortical Areas with Different Degrees of Cerebral Blood Flow Reduction ». Journal of Cerebral Blood Flow & ; Metabolism 6, no 5 (octobre 1986) : 566–73. http://dx.doi.org/10.1038/jcbfm.1986.103.
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During and after 15-min occlusion of the middle cerebral artery (MCA) in cats, local CBF and neuronal activity were measured in cortical areas varying in the degree of CBF reduction. In an area within the ischemic center (primary auditory cortex, middle ectosylvian gyrus), CBF was severely suppressed. Click-induced auditory evoked potentials and evoked as well as spontaneous single-unit activity ceased within 1 min after occlusion. Recirculation resulted in a recovery of the different neurophysiological parameters with a time delay ranging from several minutes to 2 h. In two areas surrounding the ischemic focus (a visual area in the marginal gyrus and the forelimb representation area in the primary somatosensory cortex), CBF was reduced but remained above 30 ml/100 g/min during MCA occlusion. Visual flash-induced evoked potentials and somatosensory evoked potentials induced by median nerve electrical stimulation ceased in the corresponding areas with a somewhat slower time course as compared to the auditory responses and they recovered faster after recirculation. In another somatosensory area (hindlimb projection area in the primary somatosensory cortex), CBF stayed nearly at control levels during occlusion. Evoked potentials and single-unit activity induced by tibial nerve electrical stimulation decreased ∼5 min after occlusion and were abolished ∼5 min later. At that time, single-unit activity had changed to a nonresponsive pattern but persisted. However, potentials evoked transcallosally by electrical stimulation of the contralateral hemisphere were still recorded. After reopening the MCA, the recovery of neuronal functions was usually complete and occurred within ∼5 min. We conclude that attention has to be focused on those areas surrounding an acute ischemic focus that show either no or only slight CBF alterations. The functional impairment found in such areas is caused by the injury of subcortical structures leading to a cortical deafferentation. Considering the apparent lack of a CBF disturbance, such a condition should be distinguished from the so-called cortical ischemic penumbra.
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Melinte, Gabriela-Violeta, et Codrut Sarafoleanu. « Difficulties of olfactometric evaluation in patients accusing smell disorders after head trauma ». Romanian Journal of Rhinology 8, no 29 (1 mars 2018) : 39–45. http://dx.doi.org/10.2478/rjr-2018-0005.
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Abstract Head trauma is considered to be the third cause of olfactory function disorders. Olfactometric assessment in patients accusing anosmia following head injury produced by car accident or aggression is important, because most of them are involved in law trials in order to obtain financial compensations from the author. It is compulsory to use both subjective and objective olfactory evaluation methods combined with a detailed anamnesis, a complete ENT examination and a good cranio-facial imaging (computed tomography or MRI) in order to exclude malingerers and to obtain an accurate diagnosis. “Sfanta Maria” ENT Department from Bucharest is the only center in Romania where the olfactory function in completely investigated. We use chemosensory (Snap and Sniff Test and n-Butanol Dynamic Olfactometry) and electrophysiological tests (electric olfactory evoked potentials of the olfactory bulb). Unfortunately, we confront with a series of difficulties in what concerns the smell function evaluation: 1) there is scarce information in the literature regarding the olfactory electric evoked potentials; 2) the electric olfactory evoked potentials register only the electrical activity in the olfactory bulb; 3) in case of olfactory impairment medically confirmed, we cannot establish a cause-effect relationship between the disturbance and the event; 4) the most accurate electrophysiological assessment method currently available in Europe is the time-frequency analysis of chemosensory event-related potentials, but we do not dispose of the necessary equipment yet; 5) sometimes patients do not give us the informed consent for a complete olfactory evaluation.
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Chang, Pi-shan, Suellen M. Walker et Maria Fitzgerald. « Differential Suppression of Spontaneous and Noxious-evoked Somatosensory Cortical Activity by Isoflurane in the Neonatal Rat ». Anesthesiology 124, no 4 (1 avril 2016) : 885–98. http://dx.doi.org/10.1097/aln.0000000000001017.
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Abstract Background The effect of neonatal anesthesia and pain on the developing brain is of considerable clinical importance, but few studies have evaluated noxious surgical input to the infant brain under anesthesia. Herein, the authors tested the effect of increasing isoflurane concentration on spontaneous and evoked nociceptive activity in the somatosensory cortex of rats at different postnatal ages. Methods Intracortical extracellular field potentials evoked by hind paw C-fiber electrical stimulation were recorded in the rat somatosensory cortex at postnatal day (P) 7, P14, P21, and P30 during isoflurane anesthesia (n = 7 per group). The amplitudes of evoked potentials and the energies of evoked oscillations (1 to 100 Hz over 3 s) were measured after equilibration at 1.5% isoflurane and during step increases in inspired isoflurane. Responses during and after plantar hind paw incision were compared at P7 and P30 (n = 6 per group). Results At P7, cortical activity was silent at 1.5% isoflurane but noxious-evoked potentials decreased only gradually in amplitude and energy with step increases in isoflurane. The resistance of noxious-evoked potentials to isoflurane at P7 was significantly enhanced after surgical hind paw incision (69 ± 16% vs. 6 ± 1% in nonincised animals at maximum inspired isoflurane). This resistance was age dependent; at P14 to P30, noxious-evoked responses decreased sharply with increasing isoflurane (step 3 [4%] P7: 50 ± 9%, P30: 4 ± 1% of baseline). Hind paw incision at P30 sensitized noxious-evoked potentials, but this was suppressed by higher isoflurane concentrations. Conclusions Despite suppression of spontaneous activity, cortical-evoked potentials are more resistant to isoflurane in young rats and are further sensitized by surgical injury.
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Nelson, Roger D. « Evoked Potentials and GCP Event Data ». Journal of Scientific Exploration 34, no 2 (7 juin 2020) : 246–67. http://dx.doi.org/10.31275/20201475.
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Evoked potentials (EP) are measured in time-locked synchronization with repetitions of the same stimulus. The electrical measure in raw form is extremely noisy, reflecting not only responses to the imposed stimulus but also a large amount of normal, but unrelated activity. In the raw data no structure related to the stimulus is apparent, so the process is repeated many times, yielding multiple epochs that can be averaged. Such “signal averaging” reduces or washes out random fluctuations while structured variation linked to the stimulus builds up over multiple samples. The resulting pattern usually shows a large excursion preceded and followed by smaller deviations with a typical time-course relative to the stimulus.The Global Consciousness Project (GCP) maintains a network of random number generators (RNG) running constantly at about 60 locations around the world, sending streams of 200-bit trials generated each second to be archived as parallel random sequences. Standard processing for most analyses computes a network variance measure for each second across the parallel data streams. This is the raw data used to calculate a figure of merit for each formal test of the GCP hypothesis: we predict non-random structure in data taken during “global events” that engage the attention of large numbers of people. The data are combined across all seconds of the event to give a representative Z-score, and typically displayed graphically as a cumulative deviation from expectation showing the history of the data sequence. For the present work, we treat the raw data in the same way measured electrical potentials from the brain are processed to reveal temporal patterns. In both cases the signal to noise ratio is very small, requiring signal averaging to reveal structure in what otherwise appears to be random data.Applying this model to analyze GCP data from events that show significant departures from expectation, we find patterns that look like those found in EP work. While this assessment is limited to visual comparisons, the degree of similarity is striking. It suggests that human brain activity in response to stimuli may be a useful model to guide further research addressing th
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Brooks, Charles N. « Impairment Tutorial : Rating Sensory and Motor Deficits of the Upper Extremity ». Guides Newsletter 5, no 2 (1 mars 2000) : 5–7. http://dx.doi.org/10.1001/amaguidesnewsletters.2000.marapr04.
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Abstract The three components of electrodiagnosis useful in evaluation of the peripheral nervous system and spinal cord include electromyography (EMG), electroneurography (nerve conduction studies), and somatosensory evoked potentials. EMG examination involves introduction of a special recording needle into a muscle belly. Electrical potentials located within a few millimeters of the needle are picked up by an electrode and are transmitted from the muscle to amplifiers that filter and display results visually for the electromyographer. Three types of spontaneous activity in electrical potentials are of the greatest relevance: positive sharp waves, fibrillation potentials, and fasciculations (fasciculation potentials on the EMG result from irregular firing of motor units). Electromyography can help assess the status of nerve fibers indirectly, but the integrity of large myelinated sensory and motor neurons can be evaluated directly by nerve conduction studies (NCS), also known as electroneurography. NCS can assess motor neurons, sensory neurons, or mixed nerve trunks. Sensory nerve conduction velocity can be studied in a manner analogous to motor conduction velocity: sensory fibers can be directly stimulated, and the evoked response can be measured at the wrist and elbow. Somatosensory evoked potentials occasionally are useful as an adjunct to EMG and NCS in the diagnosis of peripheral nervous system pathology. These tests also are useful when it is unclear whether an individual has a true radiculopathy.
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Gad, Parag, Igor Lavrov, Prithvi Shah, Hui Zhong, Roland R. Roy, V. Reggie Edgerton et Yury Gerasimenko. « Neuromodulation of motor-evoked potentials during stepping in spinal rats ». Journal of Neurophysiology 110, no 6 (15 septembre 2013) : 1311–22. http://dx.doi.org/10.1152/jn.00169.2013.
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The rat spinal cord isolated from supraspinal control via a complete low- to midthoracic spinal cord transection produces locomotor-like patterns in the hindlimbs when facilitated pharmacologically and/or by epidural electrical stimulation. To evaluate the role of epidural electrical stimulation in enabling motor control (eEmc) for locomotion and posture, we recorded potentials evoked by epidural spinal cord stimulation in selected hindlimb muscles during stepping and standing in adult spinal rats. We hypothesized that the temporal details of the phase-dependent modulation of these evoked potentials in selected hindlimb muscles while performing a motor task in the unanesthetized state would be predictive of the potential of the spinal circuitries to generate stepping. To test this hypothesis, we characterized soleus and tibialis anterior (TA) muscle responses as middle response (MR; 4–6 ms) or late responses (LRs; >7 ms) during stepping with eEmc. We then compared these responses to the stepping parameters with and without a serotoninergic agonist (quipazine) or a glycinergic blocker (strychnine). Quipazine inhibited the MRs induced by eEmc during nonweight-bearing standing but facilitated locomotion and increased the amplitude and number of LRs induced by eEmc during stepping. Strychnine facilitated stepping and reorganized the LRs pattern in the soleus. The LRs in the TA remained relatively stable at varying loads and speeds during locomotion, whereas the LRs in the soleus were strongly modulated by both of these variables. These data suggest that LRs facilitated electrically and/or pharmacologically are not time-locked to the stimulation pulse but are highly correlated to the stepping patterns of spinal rats.
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Zhang, S., et D. Oertel. « Cartwheel and superficial stellate cells of the dorsal cochlear nucleus of mice : intracellular recordings in slices ». Journal of Neurophysiology 69, no 5 (1 mai 1993) : 1384–97. http://dx.doi.org/10.1152/jn.1993.69.5.1384.
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1. Intracellular recordings were made from identified cartwheel and stellate cells in the molecular and fusiform cell layers of the murine dorsal cochlear nucleus (DCN). The aim of the study was to identify and characterize their synaptic inputs and to learn how synaptic inputs and intrinsic electrical properties interact to generate firing patterns. 2. Eight cells labeled by the intracellular injection of biocytin were cartwheel cells. Their axon terminals extended from the deep part of the molecular layer through the fusiform cell layer. Their dendrites extended through the molecular layer and had spines. Both the dendritic and axonal arbors were small, having diameters of approximately 150 microns in the parasagittal plane. 3. When depolarized, cartwheel cells often fired bursts of rapid action potentials superimposed on a slow depolarization. The peaks of action potentials were usually overshooting. Individually occurring action potentials were followed by two afterhyperpolarizations, as in other cells of the DCN. During bursts, action potentials did not have two distinct repolarizing phases. 4. Excitatory postsynaptic potentials (EPSPs) were recorded from cartwheel cells spontaneously and after shocks to the nerve root or to the ventral cochlear nucleus (VCN). The EPSPs rose slowly. When they were suprathreshold they evoked action potentials singly or in bursts. EPSPs evoked by shocks to the nerve root or to the VCN had long latencies, the rise of EPSPs beginning between 5 and 10 ms after the shock. No inhibitory synaptic potentials, either spontaneous or driven with electrical stimulation, were detected in cells whose resting potentials were between -50 and -70 mV. 5. The locations from which excitatory input can be driven electrically are consistent with cartwheel cells receiving excitatory synaptic input from granule cells. 6. One labeled cell was a superficial stellate cell. It had smooth, straight dendrites that radiated parallel to the layers of the DCN; its axonal arbor was also planar and was restricted to the molecular layer. Both the dendritic and axonal arbors of this stellate cell were large, > 500 microns diam in the parasagittal plane. 7. The superficial stellate cell fired trains of action potentials at regular intervals that, like other cells of the DCN, were overshooting and were followed by double undershoots. 8. Shocks to the nerve root and to the surface of the VCN evoked EPSPs after 3.5 and 2 ms, respectively, in the superficial stellate cell. Chemical stimulation of the VCN also evoked excitation. No inhibitory synaptic input, spontaneous or driven, was detected.
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Gregory, Estelle H. « Evoked Olfactory Responses in Neonatal Rats ». Perceptual and Motor Skills 61, no 3_suppl (décembre 1985) : 1023–29. http://dx.doi.org/10.2466/pms.1985.61.3f.1023.
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Although there is behavioral evidence that rat pups respond to odors, the physiological basis of the response is unclear. In the present study, eight different odors were presented to 44 anesthetized rat pups between the ages of 0 and 20 days, and recordings of electrical activity were made from the olfactory bulb. The major finding was that, contrary to earlier neurophysiological findings, even on the first day of life—when spontaneous electrical activity is minimal—evoked potentials, in the form of synchronized waveforms two to four times the amplitude of the background level of spontaneous activity, can be recorded to a variety of odor stimuli.
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Cole, J. D., W. L. Merton, G. Barrett, H. A. Katifi et R. D. Treede. « Evoked potentials in a subject with a large-fibre sensory neuropathy below the neck ». Canadian Journal of Physiology and Pharmacology 73, no 2 (1 février 1995) : 234–45. http://dx.doi.org/10.1139/y95-034.
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The results from experiments in various modalities of evoked potentials are described in a subject with a complete large peripheral neuropathy below the neck. He has no tactile or position sensitivity below that level, but has retained fatigue, pain, and temperature sensation. Percutaneous electrical stimulation of peripheral nerves led to scalp recorded evoked potentials with thresholds and propagation velocities compatible with conduction along A-δ peripheral pathways. CO2 laser evoked potentials were similar to those seen in controls, further support for intact A-δ peripheral fibres. Movement-related cortical potentials (MRCPs) were recorded associated with active and passive movement of the middle finger. The former were normal, evidence that the termination of the MRCP is not dependent on peripheral feedback. By comparing passive MRCPs between controls and the subject it was possible to establish which parts of the potentials are visual and which are proprioceptive and to gain evidence of central reorganisation in the subject. Magnetic brain stimulation was used to show that the subject did not perceive induced movement, had a normal centrally originating silent period, and could focus his attention during real and imagined movement of the finger more successfully than could normal controls.Key words: sensory and motor evoked potentials, sensory neuropathy.
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Hanani, M., et N. Maudlej. « Intracellular recordings from intramural neurons in the guinea pig urinary bladder ». Journal of Neurophysiology 74, no 6 (1 décembre 1995) : 2358–65. http://dx.doi.org/10.1152/jn.1995.74.6.2358.
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1. Intracellular recordings were made from intramural neurons in the urinary bladder of guinea pigs. 2. The neurons were located in two types of ganglia: those where the cells were densely packed and those where the neurons were loosely packed. Staining of the cells by intracellular injections of markers showed that the cells had between one to three long processes and several short dendrites. 3. The resting potential measured in 230 neurons was -55.20 +/- 0.67 (SE) mV, and the input resistance was 58.37 +/- 1.78 M omega. 4. Injection of depolarizing currents from the recording electrode evoked two types of firing patterns. In 86.2% of the neurons, depolarizing currents evoked a prolonged firing of action potentials (tonic cells). In the rest of the neurons, a depolarization elicited one to three action potentials only (phasic cells). In all the cells tested, the action potentials were reversibly blocked by tetrodotoxin (TTX; 1 microM). In the presence of TTX. Ca2+ spikes were observed in 50% of the cases. 5. Single action potentials were followed by fast hyperpolarizations having mean duration of 92.7 +/- 6.0 ms and amplitude of 13.3 +/- 1.0 mV. In 62.5% of the cells repetitive firing of action potentials was followed by delayed, slow hyperpolarizations (duration 3.8 +/- 0.5 s), which were diminished by the K+ channel blocker 4-aminopyridine and in Ca+2-free high-Mg2+ medium. These results indicate that the prolonged after-spike hyperpolarizations were due to opening of Ca(2+)-induced K+ channels. 6. Electrical stimulation of nerve fiber tracts evoked fast excitatory synaptic potentials that were blocked by the nicotinic receptor antagonist hexamethonium (0.2 mM). Exogenous acetylcholine elicited depolarizations that were also blocked by hexamethonium. Nerve stimulation at frequencies of 0.1 Hz or higher caused strong facilitation of the synaptic potentials. Stimulation at 10-20 Hz did not evoke slow synaptic potentials.
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Sayenko, Dimitry G., Claudia Angeli, Susan J. Harkema, V. Reggie Edgerton et Yury P. Gerasimenko. « Neuromodulation of evoked muscle potentials induced by epidural spinal-cord stimulation in paralyzed individuals ». Journal of Neurophysiology 111, no 5 (1 mars 2014) : 1088–99. http://dx.doi.org/10.1152/jn.00489.2013.
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Epidural stimulation (ES) of the lumbosacral spinal cord has been used to facilitate standing and voluntary movement after clinically motor-complete spinal-cord injury. It seems of importance to examine how the epidurally evoked potentials are modulated in the spinal circuitry and projected to various motor pools. We hypothesized that chronically implanted electrode arrays over the lumbosacral spinal cord can be used to assess functionally spinal circuitry linked to specific motor pools. The purpose of this study was to investigate the functional and topographic organization of compound evoked potentials induced by the stimulation. Three individuals with complete motor paralysis of the lower limbs participated in the study. The evoked potentials to epidural spinal stimulation were investigated after surgery in a supine position and in one participant, during both supine and standing, with body weight load of 60%. The stimulation was delivered with intensity from 0.5 to 10 V at a frequency of 2 Hz. Recruitment curves of evoked potentials in knee and ankle muscles were collected at three localized and two wide-field stimulation configurations. Epidural electrical stimulation of rostral and caudal areas of lumbar spinal cord resulted in a selective topographical recruitment of proximal and distal leg muscles, as revealed by both magnitude and thresholds of the evoked potentials. ES activated both afferent and efferent pathways. The components of neural pathways that can mediate motor-evoked potentials were highly dependent on the stimulation parameters and sensory conditions, suggesting a weight-bearing-induced reorganization of the spinal circuitries.
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Torfs, Tom, Refet Firat Yazicioglu, Robby Vanspauwen, Floris L. Wuyts et Chris Van Hoof. « Wireless Vestibular Evoked Myogenic Potentials System ». IEEE Sensors Journal 8, no 12 (décembre 2008) : 1941–47. http://dx.doi.org/10.1109/jsen.2008.2006469.
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Brett, Barbara, et Daniel S. Barth. « Subcortical Modulation of High-Frequency (Gamma Band) Oscillating Potentials in Auditory Cortex ». Journal of Neurophysiology 78, no 2 (1 août 1997) : 573–81. http://dx.doi.org/10.1152/jn.1997.78.2.573.
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Brett, Barbara and Daniel S. Barth. Subcortical modulation of high-frequency (gamma band) oscillating potentials in auditory cortex. J. Neurophysiol. 78: 573–581, 1997. The purpose of this study was to use depth electrical stimulation and retrograde horseradish peroxidase (HRP) labeling to determine what role certain subcortical nuclei play in the neurogenesis of high-frequency gamma (∼40 Hz) oscillations in rat auditory cortex. Evoked and spontaneous electrocortical oscillations were recorded with the use of a high-spatial-resolution multichannel epipial electrode array while electrical stimulation was delivered to the posterior intralaminar (PIL) region of the ventral acoustic thalamus and to the centrolateral nucleus (CL) and the nucleus basalis (NB), which have been previously implicated in the production of cortical gamma oscillations. PIL stimulation consistently evoked gamma oscillations confined to a location between primary and secondary auditory cortex, corresponding to the region where spontaneous gamma oscillations were also recorded. Stimulation of the CL and NB did not evoke gamma oscillations in auditory cortex. HRP placed in the cortical focus of evoked gamma oscillations labeled cell bodies in the PIL, and in more lateral regions of the ventral acoustic thalamus, which on subsequent stimulation also evoked gamma oscillations in auditory cortex. No cells were labeled in either the CL or NB. These results indicate that the PIL and the lateral regions of ventral acoustic thalamus provide anatomically distinct input to auditory cortex and may play an exclusive and modality-specific role in modulating gamma oscillations in the auditory system.
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Sittiprapa, Wichian. « Evoked Potentials : Electrical Events Specific to Brain’s Receiving Sensory Input ». Journal of Artificial Intelligence 5, no 3 (15 juin 2012) : 91–98. http://dx.doi.org/10.3923/jai.2012.91.98.
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Zakharova, I., et M. E. Kornhuber. « Facilitation of late somatosensory evoked potentials by electrical train stimuli ». Neuroscience Letters 557 (décembre 2013) : 135–37. http://dx.doi.org/10.1016/j.neulet.2013.10.039.
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Gregory, N. G., et S. B. Wotton. « Effect of electrical stunning on somatosensory evoked potentials in chickens ». British Veterinary Journal 145, no 2 (mars 1989) : 159–64. http://dx.doi.org/10.1016/0007-1935(89)90098-5.
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Delechenault, P., A. M. Leroi, T. Bruna, P. Denis et J. Weber. « Cerebral potentials evoked by electrical stimulation of the anal canal ». Diseases of the Colon & ; Rectum 36, no 1 (janvier 1993) : 55–60. http://dx.doi.org/10.1007/bf02050302.
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Park, Jonas J. H., Anmin Shen et Martin Westhofen. « Promontory electrical stimulation to elicit vestibular evoked myogenic potentials (VEMPs) ». Acta Oto-Laryngologica 135, no 3 (4 février 2015) : 239–45. http://dx.doi.org/10.3109/00016489.2014.973530.
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Godfrey, R. M., et K. W. Mitchell. « Somatosensory evoked potentials to electrical stimulation of the mental nerve ». British Journal of Oral and Maxillofacial Surgery 25, no 4 (août 1987) : 300–307. http://dx.doi.org/10.1016/0266-4356(87)90069-6.
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Serio, Rosa, Flavia Mulé et Alessandra Postorino. « Noradrenergic, noncholinergic inhibitory junction potentials in rat proximal colon : role of nitric oxide ». Canadian Journal of Physiology and Pharmacology 73, no 1 (1 janvier 1995) : 79–84. http://dx.doi.org/10.1139/y95-011.
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Using a single sucrose gap apparatus, experiments were performed to determine the involvement of nitric oxide (NO) in the generation of noradrenergic, noncholinergic (NANC) inhibitory junction potentials in circular muscle of rat proximal colon. Inhibitors of NO synthase, Nω-nitro-L-arginine and its methyl ester, reduced the amplitude of the electrically evoked inhibitory junction potentials, without affecting membrane resting potential. Such an effect was stereospecific and it was prevented by L-arginine but not by D-arginine. Sodium nitroprusside induced a tetrodotoxin-resistant hyperpolarization, which was not affected by NO synthase inhibitors. Aparnin reduced sodium nitroprusside induced hyperpolarization, as well as NANC inhibitory junction potentials, and α-chymotrypsin decreased the amplitude of electrical field stimulation evoked responses. Residual responses after NO synthase inhibitors or after α-chymotrypsin were further reduced by pretreatment with α-chymotrypsin or NO synthase inhibitors, respectively. These results suggest that, in rat colonic circular muscle, NO plays an important role in NANC inhibitory junction potential generation. However, another mechanism, peptidergic in nature, is also involved.Key words: nonadrenergic noncholinergic nerves, inhibitory junction potential, nitric oxide, rat colon.
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Cukiert, A., et C. Timo-Iaria. « Electrophysiological evidence for an L-shaped interhemispheric connection in the cat ». Arquivos de Neuro-Psiquiatria 47, no 4 (décembre 1989) : 381–84. http://dx.doi.org/10.1590/s0004-282x1989000400001.
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Transcallosal potentials evoked by electrical stimulation with rectangular pulses of 1 ms, 5 c/s and variable intensity were recorded from the cortical surface in cats anesthetized with ketamine hydrochloride. Sites of stimulation and recording were selected by means of a cartesian map of most of the neocortex. In addition to the well known transcallosal projection pattern it was found that stimulation of a restricted posterior area evokes low voltage potentials over the contralateral symmetric area while high voltage potentials are recorded from a few sites located at the ipsilateral anterior cortex and from the area symmetric as to the latter. This L-shaped transcallosal connection may be involved in complex cortical processes and is compatible with effective results of partial anterior callosotomies in patients with multifocal epilepsy and frontal bisynchronism.
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Young, E. D., I. Nelken et R. A. Conley. « Somatosensory effects on neurons in dorsal cochlear nucleus ». Journal of Neurophysiology 73, no 2 (1 février 1995) : 743–65. http://dx.doi.org/10.1152/jn.1995.73.2.743.
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1. Single units and evoked potentials were recorded in dorsal cochlear nucleus (DCN) in response to electrical stimulation of the somatosensory dorsal column and spinal trigeminal nuclei (together called MSN for medullary somatosensory nuclei) and for tactile somatosensory stimuli. Recordings were from paralyzed decerebrate cats. 2. DCN principal cells (type IV units) were strongly inhibited by electrical stimulation (single 50-microA bipolar pulse) in MSN or by somatosensory stimulation. Units recorded in the fusiform cell and deep layers of DCN were inhibited, suggesting that the inhibition affects both types of principal cells (i.e., both fusiform and giant cells). 3. Interneurons (type II units) that inhibit principal cells were only weakly inhibited by electrical stimulation and were never excited, demonstrating that the inhibitory effect on principal cells does not pass through the type II circuit. In the vicinity of the DCN/PVCN (posteroventral cochlear nucleus) boundary, units were encountered that were excited by electrical stimulation in MSN; some of these neurons responded to sound, and some did not. Their response properties are consistent with the hypothesis that they are deep-layer inhibitory interneurons conveying somatosensory information to the DCN. 4. Analysis of the evoked potentials produced by electrical stimulation in MSN suggests that the somatosensory inputs activate the granule cell system of the DCN molecular layer. A model based on previous work by Klee and Rall was used to show that the distribution of evoked potentials in DCN can be explained as resulting from radial currents produced in the DCN molecular and fusiform-cell layers by synchronous activation of granule cells inputs to fusiform and cartwheel cells. Current-source density analysis of the evoked potentials is consistent with this model. Thus molecular layer interneurons (cartwheel and stellate cells) are a second possible source of inhibition to principal cells. 5. With lower stimulus levels (20 microA) and pulse-pair stimuli (50- to 100-ms interstimulus interval), three components of the inhibitory response can be recognized in both fusiform cell layer and deep layer type IV units: a short-latency inhibition that begins before the start of the evoked potential; a longer-latency inhibition whose timing corresponds to the evoked potential; and an excitatory component that occurs on the rising phase of the evoked potential. The excitatory component is usually overwhelmed by the inhibitory components and could be derived from granule cell inputs; the long-latency inhibitory component could be derived from cartwheel cells or the hypothesized deep-layer inhibitory interneurons.(ABSTRACT TRUNCATED AT 400 WORDS)
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Bell, C. C. « Mormyromast electroreceptor organs and their afferent fibers in mormyrid fish. II. Intra-axonal recordings show initial stages of central processing ». Journal of Neurophysiology 63, no 2 (1 février 1990) : 303–18. http://dx.doi.org/10.1152/jn.1990.63.2.303.
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1. Physiologically and morphologically identified primary afferent fibers from mormyromast electroreceptor organs were recorded intracellularly. The fiber recordings were made from the nerve root of the posterior lateral line nerve, where the fibers enter the brain, and from the electrosensory lateral line lobe (ELL), near the central terminals of the fibers. 2. The intracellular recordings reveal a variety of potentials, synaptic and nonsynaptic, in addition to the large orthodromic action potentials from the periphery. The goal of the present study was to describe and interpret these various potentials in mormyromast afferent fibers as a first step in understanding the processing of electrosensory information in ELL. 3. Three types of synaptic potentials were recorded inside mormyromast afferent fibers: 1) electric organ corollary discharge (EOCD) excitatory postsynaptic potentials (EPSPs), driven by the motor command that elicits the electric organ discharge (EOD); 2) EPSPs evoked by electrosensory stimulation of electroreceptors in the skin near the electroreceptor from which the recorded fiber originates or by direct stimulation of an electrosensory nerve; and 3) inhibitory postsynaptic potentials (IPSPs) evoked by electrosensory stimulation of more distant electroreceptors. These synaptic potentials can be attributed to synaptic input to postsynaptic cells in ELL that is observed inside the afferent fibers because of electrical synapses between the fibers and the postsynaptic cells. 4. The peripherally evoked EPSPs could frequently be shown to be unitary. The unitary EPSPs were identical to the orthodromic spikes in originating from a single electroreceptor, in threshold, and in latency shift with increasing stimulus intensity. These similarities suggest that the unitary EPSPs are electrotonic EPSPs caused by impulses in other mormyromast afferent fibers that terminate on some of the same postsynaptic cells as the recorded fiber. The peripherally evoked IPSPs had a longer latency than the EPSPs or orthodromic spikes, requiring the presence of an inhibitory interneuron. 5. The peripherally evoked EPSPs, both unitary and nonunitary, show absolute refractory periods of 3-8 ms, followed by relative refractory periods of approximately 8 ms, when tested with two identical stimuli to a nerve. These refractory periods are interpreted as because of refractoriness in the fine preterminal branches of the axonal arbor. 6. A depolarizing afterpotential is commonly associated with the orthodromic spike and probably results from the successful propagation of the spike into the entire terminal arbor. The depolarizing afterpotential has a refractory period that is similar to that of the peripherally evoked EPSPs and that is also interpreted as refractoriness in the fine preterminal branches.(ABSTRACT TRUNCATED AT 400 WORDS)
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Yamazaki, Yoshihiko, Yasukazu Hozumi, Kenya Kaneko, Toshimichi Sugihara, Satoshi Fujii, Kaoru Goto et Hiroshi Kato. « Modulatory effects of oligodendrocytes on the conduction velocity of action potentials along axons in the alveus of the rat hippocampal CA1 region ». Neuron Glia Biology 3, no 4 (novembre 2007) : 325–34. http://dx.doi.org/10.1017/s1740925x08000070.
Texte intégralRésumé :
AbstractLike neurons and astrocytes, oligodendrocytes have a variety of neurotransmitter receptors and ion channels. However, except for facilitating the rapid conduction of action potentials by forming myelin and buffering extracellular K+, little is known about the direct involvement of oligodendrocytes in neuronal activities. To investigate their physiological roles, we focused on oligodendrocytes in the alveus of the rat hippocampal CA1 region. These cells were found to respond to exogenously applied glutamate by depolarization through N-methyl-D-aspartate (NMDA) receptors and non-NMDA receptors. Electrical stimulation of the border between the alveus and stratum oriens evoked inward currents through several routes involving glutamate receptors and inward rectifier K+ channels. Moreover, electrical stimulation resembling in vivo activity evoked long-lasting depolarization. To examine the modulatory effects of oligodendrocytes on neuronal activities, we performed dual, whole-cell recording on CA1 pyramidal neurons and oligodendrocytes. Direct depolarization of oligodendrocytes shortened the latencies of action potentials evoked by antidromic stimulation. These results indicate that oligodendrocytes increase the conduction velocity of action potentials by a mechanism additional to saltatory conduction, and that they have active roles in information processing in the brain.
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MANCILLA, JAIME G., et PHILIP S. ULINSKI. « Role of GABAA-mediated inhibition in controlling the responses of regular spiking cells in turtle visual cortex ». Visual Neuroscience 18, no 1 (janvier 2001) : 9–24. http://dx.doi.org/10.1017/s0952523801181022.
Texte intégralRésumé :
The visual cortex of freshwater turtles contains pyramidal cells, which have a regular spiking (RS) firing pattern, and several categories of aspiny, inhibitory interneurons. The interneurons show diverse firing patterns, including the fast spiking (FS) pattern. Postsynaptic potentials (PSPs) evoked in FS cells by visual stimulation of the retina reach their peak amplitudes as much as 200 ms before PSPs in RS cells (Mancilla et al., 1998). FS cells could, consequently, control the amplitudes of light-evoked PSPs in RS cells by producing disynaptic, feedforward inhibitory postsynaptic potentials (IPSPs) that overlap in time with geniculocortical excitatory postsynaptic potentials (EPSPs). Since FS cells receive recurrent, excitatory inputs from RS cells, they could also control the amplitudes of light-evoked PSPs in RS cells via polysynaptic, feedback inhibition. The in vitro geniculocortical preparation of Pseudemys scripta was used to characterize the temporal relationships of EPSPs and IPSPs produced in RS cells by electrical activation of geniculate afferents and by diffuse light flashes presented to the retina. GABAA receptor-mediated inhibition was blocked using extracellular application of bicuculline (3.5 mM) or intracellular perfusion of picrotoxin (1 μM) in individual RS cells. Electrical stimulation of thalamic afferents produced compound PSPs. Blockade of GABAA receptor-mediated IPSPs with either bicuculline or picrotoxin provided evidence for both early and late IPSPs in RS cells. Analysis of the apparent reversal potentials of light-evoked PSPs indicated the existence of early IPSPs during the first 140–300 ms following light onset. Light responses of cells perfused with picrotoxin diverged from control light responses at about 300 ms after light onset and had maximum amplitudes that were significantly different from control light responses. These experiments indicate that the responses of RS cells to both electrical and natural stimulation of geniculate afferents are controlled by both early and late IPSPs, consistent with activation of both feedforward and feedback pathways.
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Chen, Shu Li, Zhi Zhong Wang, Li Shi et Xiao Ke Niu. « Analysis of Visual-Evoked Potentials of Primary Visual Cortex under Flash Stimulations ». Advanced Materials Research 749 (août 2013) : 328–32. http://dx.doi.org/10.4028/www.scientific.net/amr.749.328.
Texte intégralRésumé :
Visual-evoked potentials (VEPs) which is made up of electrical signals generated by the nervous system in response to a stimulus can be easily recorded from the visual cortex of the experiment animal. There are several types of VEPs, for example, flash evoked potential (FEP), pattern evoked potential [1-3]. The FEP is produced by a visual stimulation with a brief and diffuse flash light. It is frequently used to evaluate the neural activity and sensory processing in the visual system [ and to identify and characterize the changes occurring in the retina and the occipital cortex [4, 5]. VEPs can also provide a further therapeutic approach through the stimulate of monitoring neurophysiologic changes related to diseases [6, 7]. The pattern evoked potentials have been used to assess parametric characteristics of visual perception, detect neuronal irritability and diagnose neurological diseases [8-1.
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Miyakawa, H., V. Lev-Ram, N. Lasser-Ross et W. N. Ross. « Calcium transients evoked by climbing fiber and parallel fiber synaptic inputs in guinea pig cerebellar Purkinje neurons ». Journal of Neurophysiology 68, no 4 (1 octobre 1992) : 1178–89. http://dx.doi.org/10.1152/jn.1992.68.4.1178.
Texte intégralRésumé :
1. Calcium transients related to climbing fiber (CF) and parallel fiber (PF) synaptic potentials were recorded from Purkinje cells in guinea pig cerebellar slices. Transients were measured using either absorbance changes of arsenazo III or fluorescence changes of fura-2, which were injected into individual cells in the slice. 2. All-or-none somatically recorded CF potentials elicited by white matter stimulation had all-or-none Ca transients. These signals began with a delay of > or = 2 ms from the start of the electrically recorded synaptic potential. The recovery time of CF-induced arsenazo III absorbance transients was < 50 ms in the fine dendrites in conditions that minimized the effects of dye buffering. 3. Ca2+ entry through voltage-gated Ca channels opened by Ca action potentials was the dominant source of the rise in [Ca2+]i after CF activation. There was no significant change in [Ca2+]i corresponding to the plateau potential that followed the large CF response. 4. The appearance and amplitude of distal CF-evoked Ca signals was more variable than proximal signals, suggesting that CF potentials do not reliably spread to the fine distal dendrites. The distal transient could be enhanced by intrasomatic depolarizing pulses, suggesting that it was a property of the postsynaptic membrane and not the presynaptic side of the CF synapse that was responsible for this variability. 5. Parallel fiber responses were evoked by electrical stimulation near the pial surface. Graded synaptic potentials and related Ca transients were reversibly blocked by 2 microM 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). Small synaptic potentials induced small, localized Ca transients. With increasing stimulus intensity, the PF electrical response developed a regenerative component. Larger dendritic Ca transients were detected corresponding to this component. Ca transients evoked by the regenerative responses had the same rapid rise times and fall times as those related to somatically stimulated Ca action potentials, suggesting that they also were due to Ca2+ entry through voltage-sensitive channels. 6. During trains of PF responses, we observed an increase in the spatial extent of related Ca transients. This effect could be modulated by changes in the resting potential, suggesting that the same intrinsic mechanism was affecting the spread of both CF and PF signals.