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The effects of neck flexion on cerebral potentials evoked by visual, auditory and somatosensory stimuli and focal brain blood flow in related sensory cortices  [cached]
Fujiwara Katsuo,Kunita Kenji,Kiyota Naoe,Mammadova Aida
Journal of Physiological Anthropology , 2012, DOI: 10.1186/1880-6805-31-31
Abstract: Background A flexed neck posture leads to non-specific activation of the brain. Sensory evoked cerebral potentials and focal brain blood flow have been used to evaluate the activation of the sensory cortex. We investigated the effects of a flexed neck posture on the cerebral potentials evoked by visual, auditory and somatosensory stimuli and focal brain blood flow in the related sensory cortices. Methods Twelve healthy young adults received right visual hemi-field, binaural auditory and left median nerve stimuli while sitting with the neck in a resting and flexed (20° flexion) position. Sensory evoked potentials were recorded from the right occipital region, Cz in accordance with the international 10–20 system, and 2 cm posterior from C4, during visual, auditory and somatosensory stimulations. The oxidative-hemoglobin concentration was measured in the respective sensory cortex using near-infrared spectroscopy. Results Latencies of the late component of all sensory evoked potentials significantly shortened, and the amplitude of auditory evoked potentials increased when the neck was in a flexed position. Oxidative-hemoglobin concentrations in the left and right visual cortices were higher during visual stimulation in the flexed neck position. The left visual cortex is responsible for receiving the visual information. In addition, oxidative-hemoglobin concentrations in the bilateral auditory cortex during auditory stimulation, and in the right somatosensory cortex during somatosensory stimulation, were higher in the flexed neck position. Conclusions Visual, auditory and somatosensory pathways were activated by neck flexion. The sensory cortices were selectively activated, reflecting the modalities in sensory projection to the cerebral cortex and inter-hemispheric connections.
Electrical neurostimulation for chronic pain: on selective relay of sensory neural activities in myelinated nerve fibers  [PDF]
Pierre Sacré,Sridevi V. Sarma,Yun Guan,William S. Anderson
Quantitative Biology , 2015,
Abstract: Chronic pain affects about 100 million adults in the US. Despite their great need, neuropharmacology and neurostimulation therapies for chronic pain have been associated with suboptimal efficacy and limited long-term success, as their mechanisms of action are unclear. Yet current computational models of pain transmission suffer from several limitations. In particular, dorsal column models do not include the fundamental underlying sensory activity traveling in these nerve fibers. We developed a (simple) simulation test bed of electrical neurostimulation of myelinated nerve fibers with underlying sensory activity. This paper reports our findings so far. Interactions between stimulation-evoked and underlying activities are mainly due to collisions of action potentials and losses of excitability due to the refractory period following an action potential. In addition, intuitively, the reliability of sensory activity decreases as the stimulation frequency increases. This first step opens the door to a better understanding of pain transmission and its modulation by neurostimulation therapies.
Primary Sensory and Motor Cortex Excitability Are Co-Modulated in Response to Peripheral Electrical Nerve Stimulation  [PDF]
Siobhan M. Schabrun, Michael C. Ridding, Mary P. Galea, Paul W. Hodges, Lucinda S. Chipchase
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0051298
Abstract: Peripheral electrical stimulation (PES) is a common clinical technique known to induce changes in corticomotor excitability; PES applied to induce a tetanic motor contraction increases, and PES at sub-motor threshold (sensory) intensities decreases, corticomotor excitability. Understanding of the mechanisms underlying these opposite changes in corticomotor excitability remains elusive. Modulation of primary sensory cortex (S1) excitability could underlie altered corticomotor excitability with PES. Here we examined whether changes in primary sensory (S1) and motor (M1) cortex excitability follow the same time-course when PES is applied using identical stimulus parameters. Corticomotor excitability was measured using transcranial magnetic stimulation (TMS) and sensory cortex excitability using somatosensory evoked potentials (SEPs) before and after 30 min of PES to right abductor pollicis brevis (APB). Two PES paradigms were tested in separate sessions; PES sufficient to induce a tetanic motor contraction (30–50 Hz; strong motor intensity) and PES at sub motor-threshold intensity (100 Hz). PES applied to induce strong activation of APB increased the size of the N20-P25 component, thought to reflect sensory processing at cortical level, and increased corticomotor excitability. PES at sensory intensity decreased the size of the P25-N33 component and reduced corticomotor excitability. A positive correlation was observed between the changes in amplitude of the cortical SEP components and corticomotor excitability following sensory and motor PES. Sensory PES also increased the sub-cortical P14-N20 SEP component. These findings provide evidence that PES results in co-modulation of S1 and M1 excitability, possibly due to cortico-cortical projections between S1 and M1. This mechanism may underpin changes in corticomotor excitability in response to afferent input generated by PES.
A comparison of nerve conduction studies and somatosensory evoked potentials in the diagnosis of meralgia paresthetica
Journal of Neurological Sciences , 2003,
Abstract: Nerve conduction studies of lateral femoral cutaneus nerve (LFCN) and somatosensory evoked potentials (SEP) evoked by electrical stimulation of LFCN are main electrophysiological methods used in the diagnosis of meralgia paresthetica (MP). However, the reliability of these methods is disputatious. The aim of this study is to compare the diagnostic sensitivities of sensory nerve conduction studies of LFCN and LFCN SEPs in patients with MP. Fifteen patients with clinically defined MP and 20 control subjects were studied with both methods. The onset latency, peak to peak amplitude and interside differences of sensory nerve action potential (SNAP) of LFCN, peak latency, peak to peak amplitude and interside differences of first cortical component of SEP (Fz/Cz derivation recording) (P0) were analyzed. All patients showed NCS abnormalities. Unrecordable SNAPs and alterations in the amplitude of LFCN SNAP was more frequently observed abnormalities in patients with MP. SEP abnormalities were observed in 12/15 patients (80%). Increased interside differences of peak latency of P0 component was most useful parameter among the SEP parameters. Our results suggest that nerve conduction study of LFCN is a more reliable parameter in the diagnosis of MP.
Predictability of Painful Stimulation Modulates the Somatosensory-Evoked Potential in the Rat  [PDF]
Manon W. H. Schaap, Hugo van Oostrom, Arie Doornenbal, Annemarie M. Baars, Saskia S. Arndt, Ludo J. Hellebrekers
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0061487
Abstract: Somatosensory-evoked potentials (SEPs) are used in humans and animals to increase knowledge about nociception and pain. Since the SEP in humans increases when noxious stimuli are administered unpredictably, predictability potentially influences the SEP in animals as well. To assess the effect of predictability on the SEP in animals, classical fear conditioning was applied to compare SEPs between rats receiving SEP-evoking electrical stimuli either predictably or unpredictably. As in humans, the rat’s SEP increased when SEP-evoking stimuli were administered unpredictably. These data support the hypothesis that the predictability of noxious stimuli plays a distinctive role in the processing of these stimuli in animals. The influence of predictability should be considered when studying nociception and pain in animals. Additionally, this finding suggests that animals confronted with (un)predictable noxious stimuli can be used to investigate the mechanisms underlying the influence of predictability on central processing of noxious stimuli.
Somatosensory Evoked Potentials suppression due to remifentanil during spinal operations; a prospective clinical study
Irene Asouhidou, Vasilios Katsaridis, Georgios Vaidis, Polimnia Ioannou, Panagiotis Givissis, Anastasios Christodoulou, Georgios Georgiadis
Scoliosis , 2010, DOI: 10.1186/1748-7161-5-8
Abstract: Ten patients underwent spinal surgery. Anesthesia was induced with propofol (2 mg/Kg), fentanyl (2 mcg/Kg) and a single dose of cis-atracurium (0.15 mg/Kg), followed by infusion of 0.8 mcg/kg/min of remifentanil and propofol (30-50 mcg/kg/min). The depth of anesthesia was monitored by Bispectral Index (BIS) and an adequate level (40-50) of anesthesia was maintained. Somatosensory evoked potentials (SSEPs) were recorded intraoperatively from the tibial nerve (P37) 15 min before initiation of remifentanil infusion. Data were analysed over that period.Remifentanil induced prolongation of the tibial SSEP latency which however was not significant (p > 0.05). The suppression of the amplitude was significant (p < 0.001), varying from 20-80% with this decrease being time related.Remifentanil in high doses induces significant changes in SSEP components that should be taken under consideration during intraoperative neuromonitoring.Electrophysiological monitoring is applied during spinal surgery in order to assess the nervous tissue at risk for injury in a patient who is unable to respond due to anesthesia. There are several tests that can be performed intraoperatively to indicate a probable spinal injury; the so-called "wake up" test is time consuming and can not be performed at any time or in the emergency setting while motor evoked potentials (MEPs) are extremely sensitive to anesthetic agents. Somatosensory evoked potentials (SSEP) measure the integrity of the sensory pathways in the dorsal columns of the spinal cord, by stimulating a peripheral sensory nerve and measuring the electrical response in the brain. The introduction of SSEP monitoring to spinal surgery has significantly reduced the rate of intraoperative injury. A survey of the Scoliosis Research Society and the European Spinal Deformities Society documented a reduction in injury rate from 0.7-4.0% in the pre-SSEP monitoring days to less than 0.55% with SSEP monitoring [1].SSEP are less affected by anesthetic ag
Amplitude Changes of the Electrically Evoked Compound Action Potential in Children with Cochlear Implants: Preliminary Results
Alireza Pourjavid,Mansoureh Adel Ghahraman,Mahin Sedaie,Hessam-Al-Din Emamjome
Iranian Journal of Pediatrics , 2011,
Abstract: Objective:Use of electrical instead of acoustical stimulation has made much objective electrophysiological evaluation possible. This is useful for management process of young children before and after the cochlear implant. These evaluations have been used for assessment of neuronal survival before cochlear implant and for monitoring of prosthesis function during and after the surgery. Electrically evoked compound action potential is one of these tests which makes a valid and reliable objective evaluation possible. The aim of this study was to evaluate the potentials amplitude changes three months after receiving the device in pediatric cochlear implant recipients. Methods:In this longitudinal study, changes of the potentials amplitude in four given electrodes in four sessions after receiving the device are evaluated by approximately one month intervals in children implanted in Amir Alam and Hazrat-e-Rasoul hospitals, Tehran in July to December 2007. Findings:The mean amplitude of the electrodes did not significantly change in different sessions, while there was significant difference between the first and the other electrodes responses in every session (P<0.05). Conclusion:Due to high reliability of the responses, the clinician can fit the speech processor for a long time. Better responses in apical electrodes may lead to develop an effective coding strategy.
Neuronal intrinsic properties shape naturally evoked sensory inputs in the dorsal horn of the spinal cord  [PDF]
Cecilia Reali,Raúl E. Russo
Frontiers in Cellular Neuroscience , 2013, DOI: 10.3389/fncel.2013.00276
Abstract: Intrinsic electrophysiological properties arising from specific combinations of voltage-gated channels are fundamental for the performance of small neural networks in invertebrates, but their role in large-scale vertebrate circuits remains controversial. Although spinal neurons have complex intrinsic properties, some tasks produce high-conductance states that override intrinsic conductances, minimizing their contribution to network function. Because the detection and coding of somato-sensory information at early stages probably involves a relatively small number of neurons, we speculated that intrinsic electrophysiological properties are likely involved in the processing of sensory inputs by dorsal horn neurons (DHN). To test this idea, we took advantage of an integrated spinal cord–hindlimbs preparation from turtles allowing the combination of patch-clamp recordings of DHN embedded in an intact network, with accurate control of the extracellular milieu. We found that plateau potentials and low threshold spikes (LTS) -mediated by L- and T-type Ca2+channels, respectively- generated complex dynamics by interacting with naturally evoked synaptic potentials. Inhibitory receptive fields could be changed in sign by activation of the LTS. On the other hand, the plateau potential transformed sensory signals in the time domain by generating persistent activity triggered on and off by brief sensory inputs and windup of the response to repetitive sensory stimulation. Our findings suggest that intrinsic properties dynamically shape sensory inputs and thus represent a major building block for sensory processing by DHN. Intrinsic conductances in DHN appear to provide a mechanism for plastic phenomena such as dynamic receptive fields and sensitization to pain.
Evaluation of the Electrically Evoked Action Potential Threshold Changes in Three Months after Receiving the Device in Children with Cochlear Implant
Alireza Pourjavid,Mansoureh Adel Ghahraman,Hessam-el-din Emamjome,Mahin Sedaie
Audiology , 2009,
Abstract: Background and Aim: In neural response telemetry (NRT), intracochlear electrodes stimulate the auditory nerve and record the neural responses. The electrical stimulation send to the auditory nerve by an electrode and the resulted response, called electrically evoked compound action potential (ECAP), is recorded by an adjacent electrode. The most important clinical applications of this test are evaluation and monitoring the intra and postoperative responses of auditory nerve and help to primary setting of speech processor. The aim of this study was evaluating of the potential's threshold changes in three monthes after receiving the devise in pediatric cochlear implant recipients.Materials and Methods: This longitudinal study evaluated the potential's threshold in four given electrodes in four sessions after receiving the device by approximately one months intervals in children implanted in Amir Alam and Hazrat-e-Rasoul hospitals in 2007, July to December.Results: ECAP mean threshold level of each electrode did not significantly change in differnent sessions, while there was significant difference between apical and basal electrodes’ responses in every session(p<0.001).Conclusion: The reliabiliy of the responses result in more certainty of clinician to fit the speech processor for a long time. Better responses in apical electrodes may lead to develope an effective coding strategy.
Characterization of the time course of changes of the evoked electrical activity in a model of a chemically-induced neuronal plasticity
Frédéric D Broccard, Silvia Pegoraro, Maria Ruaro, Claudio Altafini, Vincent Torre
BMC Research Notes , 2009, DOI: 10.1186/1756-0500-2-13
Abstract: In the present manuscript we analysed the time course of changes of the evoked electrical activity during neuronal plasticity and we correlated it with a transcriptional analysis of the underlying changes of gene expression. Our investigation shows that treatment for 30 min. with the GABAA receptor antagonist gabazine (GabT) causes a potentiation of the evoked electrical activity occurring 2–4 hours after GabT and the concomitant up-regulation of 342 genes. Inhibition of the ERK1/2 pathway reduced but did not abolish the potentiation of the evoked response caused by GabT. In fact not all the genes analysed were blocked by ERK1/2 inhibitors.These results are in agreement with the notion that neuronal plasticity is mediated by several distinct pathways working in unison.We have used dissociated neuronal cultures grown over MEA for 2–6 weeks to monitor the electrical activity from a population of neurons [9]. MEAs allow stable and long lasting recordings (hours to days) of extracellular signals from the entire population and permit to characterize and follow the properties of single spikes from identified neurons. In this way, it was possible to describe the global properties of the network, such as its overall electrical activity and to obtain a characterization of changes during neuronal plasticity of single identified spikes. This analysis could not be performed with hippocampal slices or organotypic cultures grown on MEAs or in vivo, because in these cases local field potentials (LFPs) are observed and a detailed investigation of neuronal plasticity at a single spike level is almost impossible. We increased synaptic efficacy and the overall electrical activity by treating hippocampal cultures for 30 min. with the GABAA receptor antagonist gabazine (GabT). After GabT, gabazine was washed out and the time course of evoked electrical activity was followed/studied. MEA's extracellular electrodes were used for recording and stimulation so to quantify changes of the evok
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