Amplitude Of Sensory Evoked Potentials Research Articles

A Novel Sensory Wave (P25) in Myelin Oligodendrocyte Glycoprotein-induced Experimental Autoimmune Encephalomyelitis Murine Model

Myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE) is a murine model for multiple sclerosis. This model is characterized by chronic and progressive demyelination, leading to impairment of motor function and paralysis. While the outcomes of the disease, including impaired motor function and immunological changes, are well-characterized, little is known about the impact of EAE on the electrophysiology of the motor and sensory systems. In this study, we assessed evoked potentials as a quantitative marker for in vivo monitoring of nervous system damage. Motor-evoked potentials (MEPs) and sensory-evoked potentials (SEPs) were first standardized in naïve C57BL mice and studied thoroughly in EAE mice. The duration of MEPs and the number of connotative potentials increased significantly alongside an increase in temporal SEP amplitudes. Moreover, a new SEP wave was identified in naïve animals, which significantly increased in MOG-induced EAE animals with no or mild symptoms (clinical score 0–2, 0–5 scale). This wave occurred ∼25 milliseconds poststimulation, thus named p25. P25 was correlated with increased vocalization and was also reduced in amplitude following treatment with morphine. As the EAE score progressed (clinical score 3–4, 0–5 scale), the amplitude of MEPs and SEPs decreased drastically. Our results demonstrate that desynchronized neural motor activity, along with hypersensitivity in the early stages of EAE, leads to a complete loss of motor and sensory functions in the late stages of the disease. The findings also suggest an increase in p25 amplitude before motor deficits appear, indicating SEP as a predictive marker for disease progression. PerspectiveThis article assesses p25, a new sensory electrophysiology wave that correlates with pain-related behavior in MOG-induced EAE mice and appears prior to the clinical symptoms. Motor electrophysiology correlates with traditional motor behavior scoring and histology.

Immediate and after effects of transcranial direct-current stimulation in the mouse primary somatosensory cortex

Transcranial direct-current stimulation (tDCS) is a non-invasive brain stimulation technique consisting in the application of weak electric currents on the scalp. Although previous studies have demonstrated the clinical value of tDCS for modulating sensory, motor, and cognitive functions, there are still huge gaps in the knowledge of the underlying physiological mechanisms. To define the immediate impact as well as the after effects of tDCS on sensory processing, we first performed electrophysiological recordings in primary somatosensory cortex (S1) of alert mice during and after administration of S1-tDCS, and followed up with immunohistochemical analysis of the stimulated brain regions. During the application of cathodal and anodal transcranial currents we observed polarity-specific bidirectional changes in the N1 component of the sensory-evoked potentials (SEPs) and associated gamma oscillations. On the other hand, 20 min of cathodal stimulation produced significant after-effects including a decreased SEP amplitude for up to 30 min, a power reduction in the 20–80 Hz range and a decrease in gamma event related synchronization (ERS). In contrast, no significant changes in SEP amplitude or power analysis were observed after anodal stimulation except for a significant increase in gamma ERS after tDCS cessation. The polarity-specific differences of these after effects were corroborated by immunohistochemical analysis, which revealed an unbalance of GAD 65–67 immunoreactivity between the stimulated versus non-stimulated S1 region only after cathodal tDCS. These results highlight the differences between immediate and after effects of tDCS, as well as the asymmetric after effects induced by anodal and cathodal stimulation.

Role of argatroban in repair of spinal cord injury in rats

Objective To investigate the effect of argatroban in repair of spinal cord injury in rats. Methods A total of 54 female Wistar rats were selected and divided into three groups according to the random number table: sham group, injury group and Argatroban group, with 18 rats in each group. The sham group only took the T10lamina; the injury group used the spinal cord injury device to make the rat spinal cord injury model; the Argatroban group received Argatroban treatment after spinal cord injury. The recovery of hindlimb motor function was evaluated by BBB score and clined plate test before injury and 7, 14, 21, 28, 35 and 42 days after injury. The sensory evoked potentials (SEP) and motor evoked potentials (MEP) were detected 42 days after operation. HE staining was used to compare the size of the cavity in the local region 42 days after injury. Results At day 7 after injury, the BBB score was (3.7±0.5)points and the inclined plane test was (28.0±2.6)° in the Argatroban group, which were better than those in the injury group [(3.3±0.5)points, (24.3±1.9)°] (P<0.05). At day 42 after injury, the BBB score was (13.0±0.8)points and inclined plane test was (50.7±2.7)° in the Argatroban group, which were significantly better than those in the injury group [(9.7±1.3) points, (40.5±2.7)°] (P<0.05). But all the above values in the Argatroban group were significantly lower than those in the sham group [(21.0±0.0)points, (60.0±0.0)°](P<0.05). At day 42 after operation, the SEP latency [(25.0±0.9)ms] in the Argatroban group was significantly shorter than that in the injury group [(31.5±1.9) ms]; the amplitude [(2.1±0.1)μV] in the Argatroban group was lower than that in the injury group [(0.5±0.1)μV] (P<0.05). The MEP latency [(11.5±1.0)ms] in the Argatroban group was significantly shorter than that in the injury group [(17.5±1.1)ms], and the amplitude [(4.8±0.8)μV] in the Argatroban group was lower than that in the injury group [(2.8±0.7)μV] (P<0.05). And the SEP or MEP latency and amplitude in the Argatroban group showed significant differences compared to the sham group [(7.5±1.0)ms, (7.5±1.0)μV](P<0.05). HE staining showed that the central area of the lesion in the Argatroban group [(0.35±0.04)mm2] was significantly smaller than that in the injury group [(0.71±0.05)mm2]. Conclusion After spinal cord injury, argatroban can protect the spinal cord tissue effectively in the injured area and promote recovery of sensory and motor function in the hind limbs of rats. Key words: Spinal cord injuries; Argatroban; Inflammation; Thrombin

Neurophysiological parameters of sensory perception and cognition among different modalities of learners.

INTRODUCTION:Different types of learners based on sensory modalities are observed. Cognition or physiological alterations in the sensory pathways might play its role in different modalities of visual, auditory, read and write, and kinesthetic learners which are based on different sensory modalities of perceptionOBJECTIVE:The objective of this study is to ascertain an objective parameter (neurophysiological parameters) for the classification of learners based on their preferred sensory modalityMATERIALS AND METHODS:An experimental cross-sectional study was conducted among 100 medical students. Learners were classified into visual, auditory, read-write, and kinesthetic learners based on the interpretation drawn on the basis of the VARK questionnaire. Sensory-evoked potentials (SEPs), including pattern shift visual (PSVEPs), brain stem auditory (BAEPs), short-latency somatosensory (SSEP), and event-related potentials (P300) were measured. SEPs measured in microvolts were recorded from the scalp with the help of active and reference electrodes. Multiple responses to sensory stimuli (using NIHON KOHDEN Corporation Neuropack X1, Tokyo, Japan) were recored and averaged using the computerized signal averging technique.RESULTS:No statistically significant difference was observed in conduction velocities (in terms of latency and amplitude) of SEP among different type of learners, except latency N145 wave form in VEP (P < 0.05). A characteristic pattern of minimal comparative latency was observed among the majority of visual learners. Similary, P300 has shown a characteristic pattern of decreased comparative latency among majority of read and write learners.CONCLUSION:Study findings suggested that among existing teaching and learning modalities, visual modalities were observed faster but to retain it in memory and for abstract thinking, students should utilize read and writing skills which are lacking in the era of digitalization and overuse of electronic devices.

Heterogeneous effect of increasing spinal cord perfusion pressure on sensory evoked potentials recorded from acutely injured human spinal cord

PurposeTo investigate the effect of increasing spinal cord perfusion pressure (SCPP) on sensory evoked potentials (SEPs) and injury site metabolism in patients with severe traumatic spinal cord injury TSCI. Materials and methodsIn 12 TSCI patients we placed a pressure probe, a microdialysis catheter and a strip electrode with 8 contacts on the surface of the injured cord. We monitored SCPP, lactate-to-pyruvate ratio (LPR) and SEPs (after median or posterior tibial nerve stimulation). ResultsIncrease in SCPP by ~20 mmHg produced a heterogeneous response in SEPs and injury site metabolism. In some patients, SEP amplitudes increased and the LPR decreased indicating improved tissue metabolism. In others, SEP amplitudes decreased and the LPR increased indicating more impaired metabolism. Compared with patients who did not improve at follow-up, those who improved had significantly more electrode contacts with SEP amplitude increase in response to increasing SCPP. ConclusionsIncreasing SCPP after acute, severe TSCI may be beneficial (if associated with increase in SEP amplitude) or detrimental (if associated with decrease in SEP amplitude). Our findings support individualized management of patients with acute, severe TSCI guided by monitoring from the injury site rather than applying universal blood pressure targets as is current clinical practice.

SENSORY ATTENUATION ASSESSED BY SENSORY EVOKED POTENTIALS IN FUNCTIONAL MOVEMENT DISORDERS

ObjectiveFunctional (psychogenic) movement disorders (FMD) have features associated with voluntary movement (e.g. distractibility) but patients report movements to be out of their control. One explanation for this phenomenon is that...

Sensory Attenuation Assessed by Sensory Evoked Potentials in Functional Movement Disorders.

BackgroundFunctional (psychogenic) movement disorders (FMD) have features associated with voluntary movement (e.g. distractibility) but patients report movements to be out of their control. One explanation for this phenomenon is that sense of agency for movement is impaired. The phenomenon of reduction in the intensity of sensory experience when movement is self-generated and a reduction in sensory evoked potentials (SEPs) amplitude at the onset of self-paced movement (sensory attenuation) have been linked to sense of agency for movement.MethodsWe compared amplitude of SEPs from median nerve stimulation at rest and at the onset of a self-paced movement of the thumb in 17 patients with FMD and 17 healthy controls.ResultsPatients showed lack of attenuation of SEPs at the onset of movement compared to reduction in amplitude of SEPs in controls. FMD patients had significantly different ratios of movement onset to rest SEPs than did healthy controls at each electrode: 0.79 in healthy controls and 1.35 in patients at F3 (t = -4.22, p<0.001), 0.78 in healthy controls and 1.12 at patients C3 (t = -3.15, p = 0.004) and 0.77 in healthy controls and 1.05 at patients P3 (t = -2.88, p = 0.007).ConclusionsPatients with FMD have reduced sensory attenuation as measured by SEPs at onset of self-paced movement. This finding can be plausibly linked to impairment of sense of agency for movement in these patients.

Transspinal direct current stimulation immediately modifies motor cortex sensorimotor maps.

Motor cortex (MCX) motor representation reorganization occurs after injury, learning, and different long-term stimulation paradigms. The neuromodulatory approach of transspinal direct current stimulation (tsDCS) has been used to promote evoked cortical motor responses. In the present study, we used cathodal tsDCS (c-tsDCS) of the rat cervical cord to determine if spinal cord activation can modify the MCX forelimb motor map. We used a finite-element method model based on coregistered high-resolution rat MRI and microcomputed tomography imaging data to predict spinal current density to target stimulation to the caudal cervical enlargement. We examined the effects of cathodal and anodal tsDCS on the H-reflex and c-tsDCS on responses evoked by intracortical microstimulation (ICMS). To determine if cervical c-tsDCS also modified MCX somatic sensory processing, we examined sensory evoked potentials (SEPs) produced by wrist electrical stimulation and induced changes in ongoing activity. Cervical c-tsDCS enhanced the H-reflex, and anodal depressed the H-reflex. Using cathodal stimulation to examine cortical effects, we found that cervical c-tsDCS immediately modified the forelimb MCX motor map, with decreased thresholds and an expanded area. c-tsDCS also increased SEP amplitude in the MCX. The magnitude of changes produced by c-tsDCS were greater on the motor than sensory response. Cervical c-tsDCS more strongly enhanced forelimb than hindlimb motor representation and had no effect on vibrissal representation. The finite-element model indicated current density localized to caudal cervical segments, informing forelimb motor selectivity. Our results suggest that c-tsDCS augments spinal excitability in a spatially selective manner and may improve voluntary motor function through MCX representational plasticity.

Gender And Peripheral Neuropathy In Chronic Alcoholism: A Clinical‐Electroneurographic Study

In some alcohol‐related pathologies of chronic alcoholism women are more vulnerable than men. A consecutive sample of 62 chronic alcoholics was studied, 18 females and 44 males, aged between 28 and 69 years to assess the incidence and distribution of peripheral neuropathy with regard to gender. All patients underwent clinical and neurological observations, laboratory tests, and electroneurography. Total lifetime dose of ethanol (TLDE) and other risk factors for neuropathy (disease duration, age, nutritional status) were calculated and correlated to sural nerve sensory‐evoked potential (SEP) amplitude. In 42 patients (67.7%), we observed the presence of clinical and/or infraclinical neuropathy, mostly axonal, in 29 males (65.9%) and 13 females (72.2%). In women, compared to men, TLDE and disease duration were significantly inversely correlated to sural nerve SEP amplitude, i.e in women, SEP amplitude is significantly reduced in relation to TLDE and disease duration increase. These data indicate a higher sensitivity of females towards the toxic effects of ethanol, other than malnutrition, on peripheral nerve fibres.

GENDER AND PERIPHERAL NEUROPATHY IN CHRONIC ALCOHOLISM: A CLINICAL-ELECTRONEUROGRAPHIC STUDY

In some alcohol-related pathologies of chronic alcoholism women are more vulnerable than men. A consecutive sample of 62 chronic alcoholics was studied, 18 females and 44 males, aged between 28 and 69 years to assess the incidence and distribution of peripheral neuropathy with regard to gender. All patients underwent clinical and neurological observations, laboratory tests, and electroneurography. Total lifetime dose of ethanol (TLDE) and other risk factors for neuropathy (disease duration, age, nutritional status) were calculated and correlated to sural nerve sensory-evoked potential (SEP) amplitude. In 42 patients (67.7%), we observed the presence of clinical and/or infraclinical neuropathy, mostly axonal, in 29 males (65.9%) and 13 females (72.2%). In women, compared to men, TLDE and disease duration were significantly inversely correlated to sural nerve SEP amplitude, i.e. in women, SEP amplitude is significantly reduced in relation to TLDE and disease duration increase. These data indicate a higher sensitivity of females towards the toxic effects of ethanol, other than malnutrition, on peripheral nerve fibres.

Neural activity in SII modifies sensory evoked potentials in SI in awake rats.

The function of the projection from the secondary somatosensory cortex (SII) to the primary somatosensory cortex (SI) in rats was investigated by recording sensory evoked potentials (SEP) in SI during glutamate activation and lidocaine blockade of SII. In anesthetized animals, glutamate stimulation of SII decreased SEP latency and increased SEP amplitude, whereas no changes were evident during lidocaine blockade of SII. In awake animals, a second, later component of the SEP appeared. This second component was almost completely eliminated during lidocaine blockade of SII. We conclude that the projection from SII to SI in rats slightly facilitates the SEP response in anesthetized animals and is responsible for a major portion of the late component of the SEP in awake animals.

Surgical Education: Scientific Dialogue++Experimental Use of Somatosensory Evoked Potential for Intraoperative Identification of Spinal Cord Blood Supply

The role of sensory evoked potentials (SEPs) to be used intraoperatively to reliably predict spinal cord ischemia, caused by interruption of intercostal and of lumbar and sacral arteries, was evaluated in a canine model. Two groups were assessed: (A) interruption of intercostal arteries (n = 6) and (B) interruption of all posterior branches (n = 6). SEPs were evaluated intraoperatively as control and interruption of posterior vessel groups, and at 18-22 h after surgery. Neurologic assessment was performed preoperatively and 18-22 h postoperatively by modified Tarlov criteria. Morphological assessments were also performed. The assessment of the groups demonstrated prolongation of latency and loss of amplitude of SEP, but individual changes of SEPs were poor predictors of paraplegia. Ultrastructural changes correlated with neurologic findings. SEPs were unreliable for intraoperative identification of vessels critical to spinal cord blood supply, possibly related to anatomically different blood supply of sensory and motor tracts.

Effect of a subdural air collection on the sensory evoked potential during surgery in the siting position

Fifty-three cases with posterior fossa surgery were monitored using sensory evoked potentials (SEPs) and auditory evoked potentials (AEPs) simultaneously. Nine of them operated in the sitting position showed typical SEP changes during intracranial manipulations that were not attributable either to surgical or to anaesthetic handling. The SEP amplitude rapidly recovered when the patients were laid supine after operation. Skull X rays revealed intracranial air collections beneath the recording electrodes. The SEP changes were considered to be caused by conduction hindrance by the subdural air. In 1 patient, a way to overcome the air problem was demonstrated: bitemporal recording (T3-T4 montage) revealed little change in the SEP despite subdural air while the simultaneously recorded parieto-frontal record showed a drastic change.

Vitesses de conduction sensitive normales des nerfs median et cubital chez l'enfant de la naissance a quinze ans

Conduction velocity of the fastest fibres in sensory nerves (SCV), amplitude and shape of the sensory evoked potentials (SEPs) were studied in 94 normal children aged 5 days up to 15 years. Surface electrodes were used both for nerve stimulation and sensory evoked potential recording. Normal minimal value in young adults is reached between 2 and 4 years of age, earlier in the proximal segment of the nerve (wrist-elbow) than in the distal segment (digit-wrist). Amplitude of the median SEP at the wrist increases about 155% during the first 2 years of life; this increase becomes more progressive and moderate from 2 to 15 years of age. At the elbow, the SEP has a smaller amplitude and is made of two separate peaks in 80-100% of the children between 6 months and 10 years of age. The presence of those two separate components lends substance to the view that there are two groups of fibres with different degrees of maturation. Methodology and results are discussed along with previous data from the literature.