The P300 Auditory Evoked Potential in Cochlear Implant Users: A Scoping Review

Abstract Introduction The P300 auditory evoked potential is a long-latency cortical potential evoked with auditory stimulation, which provides information on neural mechanisms underlying the central auditory processing. Objectives To identify and gather scientific evidence regarding the P300 in adult cochlear implant (CI) users. Data Synthesis A total of 87 articles, 20 of which were selected for this study, were identified and exported to the Rayyan search software. Those 20 articles did not propose a homogeneous methodology, which made comparison more difficult. Most articles (60%) in this review compare CI users with typical hearing people, showing prolonged P300 latency in CI users. Among the studies, 35% show that CI users present a smaller P300 amplitude. Another variable is the influence of the kind of stimulus used to elicit P300, which was prolonged in 30% of the studies that used pure tone stimuli, 10% of the studies that used pure tone and speech stimuli, and 60% of the studies that used speech stimuli. Conclusion This review has contributed with evidence that shows the importance of applying a controlled P300 protocol to diagnose and monitor CI users. Regardless of the stimuli used to elicit P300, we noticed a pattern in the increase in latency and decrease in amplitude in CI users. The user's experience with the CI speech processor over time and the speech test results seem to be related to the P300 latency and amplitude measurements.

The Effects of Monaural Stimulation on Frequency-Following Responses in Adults Who Can Sing in Tune and Those Who Cannot

Abstract Introduction Musicians have an advantage over non-musicians in detecting, perceiving, and processing nonverbal (i.e., environmental sounds, tones and others) and verbal sounds (i.e., consonant, vowel, phrases and others) as well as instrumental sounds. In contrast to the high skill of musicians, there is another group of people who are tone-deaf and have difficulty in distinguishing musical sounds or singing in tune. These sounds can originate in different ways, such as a musical instrument, orchestra, or the human voice. Objectives The objective of the present work is to study frequency-following responses (FFRs) in individuals who can sing in-tune and those who sing off-tune. Methods Electrophysiological responses were recorded in 37 individuals divided in two groups: (i) control group (CG) with professional musicians, and (ii) experimental group (EG) with non-musicians. Results There was homogeneity between the two groups regarding age and gender. The CG had more homogeneous responses in the latency of the FFRs waves when responses between the right and left ears were compared to those of the EG. Conclusions This study showed that monaural stimulation (right or left) in an FFR test is useful for demonstrating impairment of speech perception in individuals who sing off tune. The response of the left ear appears to present more subtlety and reliability when identifying the coding of speech sound in individuals who sing off tune.

Role of visual evoked potential as a window to detect functional changes that occur without signs of diabetic retinopathy in fundoscopy: Case series involving symptomatic overt diabetic pregnant women

Diabetic retinopathy (DR) is a microvascular complication associated with diabetes mellitus. Pregnancy is a major risk factor for DR in diabetic women. Recent evidenced suggests that in course of DR functional changes including damage of pre-ganglionic and ganglionic cells in retina precede structural microvascular changes. A number of studies in the past have highlighted the role of pattern visual evoked potential (VEP) in detecting such functional changes. However, the study of VEP changes in diabetic pregnancies remains unexplored. This case series has the objective of exploring VEP changes in symptomatic OVD cases, who had no signs of DR on fundoscopy. We present two cases of overt diabetic women who complaint of straining of eyes, headache, and difficulty in reading during pregnancy. Complete ophthalmic examination was done in both the cases followed by a VEP test. VEP test was done as a part of a research project. The ethical clearance for the project was obtained from the Institute’s Ethics Committee before the commencement of the study. Fundoscopic examination in both cases revealed that the retina was within normal limits with no signs of retinopathy. In Case 1, P100 latency was increased for the left eye and was normal for the right eye during the first visit. While P100 latency was increased for both left and right eye during the second visit. There was a substantial increase in P100 latency for both eyes in second visit as compared to first visit. In Case 2, P100 latency was increased for both left and right eye and amplitude decreased for the left eye. This is a case series consisting of symptomatic overt diabetic pregnant women who had increased P100 latency despite no signs of retinopathy in fundoscopy. The previous studies have reported that multiple follow-ups with ophthalmoscopy may not be cost-effective in diabetic pregnant women. VEP provides a window for detection of early functional changes that may help identify at risk patients for follow-up and early intervention.

Visual function changes of dysthyroid optic neuropathy and ROC curve analysis for early diagnostic indicators / 中南大学学报(医学版)

OBJECTIVES@#Dysthyroid optic neuropathy (DON) is a class of diseases that makes seriously endanger to the vision of patients with thyroid-associated ophthalmopathy. This study aims to observe the visual function changes in patients with DON, and to evaluate the diagnostic value of indicators diagnosing DON.@*METHODS@#A retrospective study was conducted on 98 eyes of 49 patients with dysthyroid optic neuropathy (DON) who were treated in Xiangya Hospital of Central South University from January 2017 to December 2019. All patients were received the examination of best corrected visual acuity (BCVA), Humphrey visual field, visual evoked potential (VEP), and contrast sensitivity. Ninety-eight eyes were divided into a DON group (45 eyes) and a non-DON group (53 eyes). T-test was used to compare the related indicators between the 2 groups. The sensitivity and specificity of each indicator were analyzed by receiver operating characteristic (ROC) curve.@*RESULTS@#The BCVA and visual field index (VFI) of the DON group were significantly lower than those of the non-DON group (all P<0.05). The mean deviation (MD) and pattern standard deviation (PSD) of the DON group were significantly higher than those of the non-DON group (all P<0.05). The low frequency contrast sensitivity (CSL), medium frequency contrast sensitivity (CSM), and high frequency contrast sensitivity (CSH) of the DON group were significantly lower than those of the non-DON group (all P<0.05), with CSH being particularly prominent. Compared with the non-DON group, at spatial frequencies of 15°, 30°, and 60°, the amplitude of N135 wave was significantly reduced, and the latency of N75 wave, P100 wave, and N135 wave was significantly prolonged in the DON group (all P<0.05); at spatial frequencies of 15° and 30°, the amplitude of P100 wave was significantly reduced in the DON group (P<0.05). The ROC curve analysis results showed that the area under the curve (AUC) of VFI, CSL, CSM, CSH and 15° P100 amplitude diagnosing DON were 0.812, 0.841, 0.880, 0.784, and 0.791, respectively, with CSM possessing the highest sensitivity and specificity.@*CONCLUSIONS@#The visual function of patients with DON is decreased. VFI, contrast sensitivity of low, medium, and high frequency, and 15° P100 wave amplitude might be effective indicators for early diagnosis of DON.

Effects of transcranial magnetic stimulation on the swallowing and brain-stem auditory evoked potentials of dysphagic stroke survivors / 中华物理医学与康复杂志

Objective:To observe any effects of contralateral repeated transcranial magnetic stimulation (rTMS) of the swallowing motor cortex on the swallowing and brainstem auditory evoked potentials (BAEPs) of stroke survivors with dysphagia.Methods:A total of 83 stroke survivors with dysphagia were randomly divided into an ipsilesional stimulation group ( n=22), a contralesional stimulation group ( n=21), a bilateral stimulation group ( n=20), and a control group ( n=20). In addition to their conventional dysphagia training, those in the three stimulation groups received 3Hz rTMS while the control group was given fake stimulation. The treatment was administered daily for 20 minutes, 6 days a week, for 5 consecutive weeks. Before and after the treatment, swallowing function was assessed videofluoroscopically and using the Dysphagia Outcome and Severity Scale (DOSS). The oral and pharyngeal stages of swallowing were evaluated using the videofluoroscopic dysphagia scale (VDS). Brain stem conduction was assessed using BAEPs. Results:After treatment the average DOSS scores of all 4 groups were significantly better than before the treatment. The average DOSS scores of the contralesional and bilateral sti-mulation groups were then significantly better than those of the other two groups. The sub-item and total VDS scores of all 4 groups had decreased significantly, but the average score of the bilateral stimulation group was significantly lower than the control group′s average. Ipsilesional stimulation significantly improved the VDS sub-item scores for the triggering of pharyngeal swallowing, laryngeal elevation, and pharyngeal transit time compared with the control group. In the contralesional stimulation group the average total score and the VDS sub-item scores for apraxia, premature bolus loss, oral transit times, the triggering of pharyngeal swallowing, vallecular residue, laryngeal elevation, coating on the pharyngeal wall, and pharyngeal transit time were significantly lower than those of the control group, on average. After the treatment the latencies of BAEP waves I, III and V and the I-III, III-V and I-V interpeak intervals had decreased significantly in all four groups, but the average latencies and intervals of the bilateral and contralesional groups were significantly shorter than those of the control group. The latencies and intervals of the bilateral stimulation group were then significantly shorter than those in the ipsilesional stimulation group on average. The average latency of wave V in the bilateral stimulation group (6.53±0.73ms) was significantly shorter than that in the contralesional stimulation group after the treatment.Conclusion:Bilateral rTMS over the swallowing motor cortex combined with conventional dysphagia training can significantly improve the swallowing of dysphagic stroke survivors.

Brain-computer interface coding method based on high-frequency dual-frequency SSVEP / 国际生物医学工程杂志

Objective:To improve the users’ comfort of steady-state visual evoked potential (SSVEP)-based brain-computer interface (BCI) through high-frequency stimulation and overcome the problem of accuracy decline caused by high frequency by combining dual-frequency encoding.Methods:Two dual-frequency high-frequency 60-instruction paradigms based on left and right visual fields and checkerboard stimuli were designed based on the 25.5 - 39.6 Hz frequency. Thirteen subjects participated in the experiment, and spectrum and spatial characteristics analyses were performed on SSVEP signals. The filter bank parameters were optimized based on the spectrum characteristics. Extended canonical correlation analysis (eCCA), ensemble task-related component analysis (eTRCA), and task-discriminant component analysis (TDCA) were used for SSVEP recognition.Results:Stable SSVEP was successfully induced in both the left and right visual fields and the checkerboard grid paradigm. The left and right visual fields had high signal-to-noise ratios for the fundamental frequency and its harmonics and weak signal-to-noise ratios for intermodulation components, whereas the intermodulation components of the 2 stimulus frequencies of the checkerboard grid, f1 + f2, had significantly higher signal-to-noise ratios than the second harmonic components above 30 Hz, and there was also a f2 ? f1 component and a 2 f1 ? f2 component. Combined with brain topography, it can be seen that the f1 and f2 response components of the left and right visual fields are located on opposite sides of the visual field, while the checkerboard grids are both concentrated in the center of the occipital region. Regarding the lateralization of brain topography amplitude and signal-to-noise ratio, the mean values of the PO3 and PO4 signal-to-noise ratios at the stimulation frequency of the left and right visual fields are consistent with the contralateral response characteristics. The 5 fb ? 1 method is the optimal filter set setting method, and the recognition correctness rate of TDCA for the left and right visual fields is the highest. However, the comparison of the recognition correctness rate of tessellated lattice eTRCA and TDCA is not statistically significant ( P > 0.05). The information transmission rates of the three algorithms all increase and then decrease with the increase in data length. Conclusions:The designed dual-frequency, high-frequency SSVEP-BCI paradigm is able to better balance performance and comfort and provides a basis for practical large instruction set BCI design methods.

Advances in brain-computer interface based on high-frequency steady-state visual evoked potential / 生物医学工程学杂志

Steady-state visual evoked potential (SSVEP) has been widely used in the research of brain-computer interface (BCI) system in recent years. The advantages of SSVEP-BCI system include high classification accuracy, fast information transform rate and strong anti-interference ability. Most of the traditional researches induce SSVEP responses in low and middle frequency bands as control signals. However, SSVEP in this frequency band may cause visual fatigue and even induce epilepsy in subjects. In contrast, high-frequency SSVEP-BCI provides a more comfortable and natural interaction despite its lower amplitude and weaker response. Therefore, it has been widely concerned by researchers in recent years. This paper summarized and analyzed the related research of high-frequency SSVEP-BCI in the past ten years from the aspects of paradigm and algorithm. Finally, the application prospect and development direction of high-frequency SSVEP were discussed and prospected.

The Value of VR-PVEP in Objective Evaluation of Monocular Refractive Visual Impairment / 法医学杂志

OBJECTIVES@#To study the virtual reality-pattern visual evoked potential (VR-PVEP) P100 waveform characteristics of monocular visual impairment with different impaired degrees under simultaneous binocular perception and monocular stimulations.@*METHODS@#A total of 55 young volunteers with normal vision (using decimal recording method, far vision ≥0.8 and near vision ≥0.5) were selected to simulate three groups of monocular refractive visual impairment by interpolation method. The sum of near and far vision ≤0.2 was Group A, the severe visual impairment group; the sum of near and far vision <0.8 was Group B, the moderate visual impairment group; and the sum of near and far vision ≥0.8 was Group C, the mild visual impairment group. The volunteers' binocular normal visions were set as the control group. The VR-PVEP P100 peak times measured by simultaneous binocular perception and monocular stimulation were compared at four spatial frequencies 16×16, 24×24, 32×32 and 64×64.@*RESULTS@#In Group A, the differences between P100 peak times of simulant visual impairment eyes and simultaneous binocular perception at 24×24, 32×32 and 64×64 spatial frequencies were statistically significant (P<0.05); and the P100 peak time of normal vision eyes at 64×64 spatial frequency was significantly different from the simulant visual impairment eyes (P<0.05). In Group B, the differences between P100 peak times of simulant visual impairment eyes and simultaneous binocular perception at 16×16, 24×24 and 64×64 spatial frequencies were statistically significant (P<0.05); and the P100 peak time of normal vision eyes at 64×64 spatial frequency was significantly different from the simulant visual impairment eyes (P<0.05). In Group C, there was no significant difference between P100 peak times of simulant visual impairment eyes and simultaneous binocular perception at all spatial frequencies (P>0.05). There was no significant difference in the P100 peak times measured at all spatial frequencies between simulant visual impairment eyes and simultaneous binocular perception in the control group (P>0.05).@*CONCLUSIONS@#VR-PVEP can be used for visual acuity evaluation of patients with severe and moderate monocular visual impairment, which can reflect the visual impairment degree caused by ametropia. VR-PVEP has application value in the objective evaluation of visual function and forensic clinical identification.

Application Progress of Objective Audiological Detection Techniques in Forensic Clinical Medicine / 法医学杂志

The qualitative, quantitative, and localization analysis of hearing loss is one of the important contents of forensic clinical research and identification. Pure-tone audiometry is the "gold standard" for hearing loss assessment, but it is affected by the subjective cooperation of the assessed person. Due to the complexity of the auditory pathway and the diversity of hearing loss, the assessment of hearing loss requires the combination of various subjective and objective audiometric techniques, along with comprehensive evaluation based on the case situation, clinical symptoms, and other examinations to ensure the scientificity, accuracy and reliability of forensic hearing impairment assessment. Objective audiometry includes acoustic impedance, otoacoustic emission, and various auditory evoked potentials. The frequency-specific auditory brainstem response (ABR), 40 Hz auditory event related potential, and auditory steady-state response are commonly used for objective hearing threshold assessment. The combined application of acoustic impedance, otoacoustic emission and ABR can be used to locate hearing loss and determine whether it is located in the middle ear, cochlea, or posterior cochlea. This article reviews the application value of objective audiometry techniques in hearing threshold assessment and hearing loss localization, aiming to provide reference for forensic identification of hearing loss.

Objective Assessment of Visual Field Defects Caused by Optic Chiasm and Its Posterior Visual Pathway Injury / 法医学杂志

OBJECTIVES@#To investigate the characteristics and objective assessment method of visual field defects caused by optic chiasm and its posterior visual pathway injury.@*METHODS@#Typical cases of visual field defects caused by injuries to the optic chiasm, optic tracts, optic radiations, and visual cortex were selected. Visual field examinations, visual evoked potential (VEP) and multifocal visual evolved potential (mfVEP) measurements, craniocerebral CT/MRI, and retinal optical coherence tomography (OCT) were performed, respectively, and the aforementioned visual electrophysiological and neuroimaging indicators were analyzed comprehensively.@*RESULTS@#The electrophysiological manifestations of visual field defects caused by optic chiasm injuries were bitemporal hemianopsia mfVEP abnormalities. The visual field defects caused by optic tract, optic radiation, and visual cortex injuries were all manifested homonymous hemianopsia mfVEP abnormalities contralateral to the lesion. Mild relative afferent pupil disorder (RAPD) and characteristic optic nerve atrophy were observed in hemianopsia patients with optic tract injuries, but not in patients with optic radiation or visual cortex injuries. Neuroimaging could provide morphological evidence of damages to the optic chiasm and its posterior visual pathway.@*CONCLUSIONS@#Visual field defects caused by optic chiasm, optic tract, optic radiation, and visual cortex injuries have their respective characteristics. The combined application of mfVEP and static visual field measurements, in combination with neuroimaging, can maximize the assessment of the location and degree of visual pathway damage, providing an effective scheme for the identification of such injuries.

Recognition of high-frequency steady-state visual evoked potential for brain-computer interface / 生物医学工程学杂志

Coding with high-frequency stimuli could alleviate the visual fatigue of users generated by the brain-computer interface (BCI) based on steady-state visual evoked potential (SSVEP). It would improve the comfort and safety of the system and has promising applications. However, most of the current advanced SSVEP decoding algorithms were compared and verified on low-frequency SSVEP datasets, and their recognition performance on high-frequency SSVEPs was still unknown. To address the aforementioned issue, electroencephalogram (EEG) data from 20 subjects were collected utilizing a high-frequency SSVEP paradigm. Then, the state-of-the-art SSVEP algorithms were compared, including 2 canonical correlation analysis algorithms, 3 task-related component analysis algorithms, and 1 task discriminant component analysis algorithm. The results indicated that they all could effectively decode high-frequency SSVEPs. Besides, there were differences in the classification performance and algorithms' speed under different conditions. This paper provides a basis for the selection of algorithms for high-frequency SSVEP-BCI, demonstrating its potential utility in developing user-friendly BCI.

The ontogenetic model for CVA rehabilitation with transcranial stimulation

Currently, transcranial stimulation for CVA treatment is based on the interhemispheric rivalry model. This model has proven to have many anomalies, necessitating a new paradigm. Spontaneous recovery from post-CVA hemiplegia has an ontogenetic pattern. We reanalyzed the 2008 longitudinal London study and found that cortical disinhibition is the mechanism for ontogenetic CVA recovery. We propose that transcranial stimulation with 10 Hz rTMS or anode electrical microstimulation can produce CVA recovery similar to spontaneous recovery. (Acta Med Colomb 2022; 47. DOI:https://doi.org/10.36104/amc.2022.2466).

Actualmente la aplicación de la estimulación transcraneal para el tratamiento del ACV se realiza con base en el modelo de rivalidad interhemisférica. Este modelo ha mostrado muchas anomalías que hacen necesario un nuevo paradigma. La recuperación espontánea de la hemiplejia post-ACV tiene patrón ontogénico. Reanalizamos el estudio longitudinal de Londres 2008 y encontramos que su propuesta corresponde al mecanismo de recuperación ontogénica del ACV. Planteamos que la estimulación transcraneal, utilizando EMTr a 10 Hz o microestimulación eléctrica anódica, podría recuperar el ACV de manera similar a la recuperación espontánea. (Acta Med Colomb 2022; 47. DOI:https://doi.org/10.36104/amc.2022.2466).

Dysthyroid optic neuropathy: Demographics, risk factors, investigations, and management outcomes

Purpose: To analyze the clinical presentations, risk factors, and management outcomes in patients presenting with dysthyroid optic neuropathy (DON). Methods: This is a retrospective, single?center study carried out on consecutive patients presenting with DON over a period of 4 years (2013–2016). The VISA classification was used at the first visit and subsequent follow?ups. The diagnosis was based on optic nerve function tests and imaging features. Demographic profiles, clinical features, risk factors, and management outcomes were analyzed. Results: Thirty?seven eyes of 26 patients diagnosed with DON were included in the study. A significant male preponderance was noted (20, 76.92%). Twenty patients (76.9%, P = 0.011) had hyperthyroidism, and 15 (57.69%, P = 0.02) were smokers. Decreased visual acuity was noted in 28 eyes (75.6%). Abnormal color vision and relative afferent pupillary defects were seen in 24 (64.86%) eyes, and visual field defects were seen in 30 (81.01%) eyes. The visual evoked potential (VEP) showed a reduced amplitude in 30 (96.77%, P = 0.001) of 31 eyes and delayed latency in 20 (64.51%, P = 0.0289) eyes. Twenty?six (70.27%) patients were treated with intravenous methyl prednisolone (IVMP) alone, whereas 11 (29.72%) needed surgical decompression. The overall best?corrected visual acuity improved by 0.2 l logMARunits. There was no statistically significant difference in outcome between medically and surgically treated groups. Four patients developed recurrent DON, and all of them were diabetics. Conclusion: Male gender, hyperthyroid state, and smoking are risk factors for developing DON. VEP, apical crowding, and optic nerve compression are sensitive indicators for diagnosing DON. Diabetics may have a more defiant course and are prone to develop recurrent DON.

Comparative study of brainstem auditory evoked responses in females having premenstrual symptoms with normal population

Background: Premenstrual symptoms (PMS) have largely been ignored, because ages so present study are done in females specifically having PMS comparing with females with no PMS. Very little work has been done in past in this field, because females revealing menstrual history are a big taboo in our society. Aim and Objective: The aim of this study was to study brainstem auditory evoked potential (BAEP) in females having premenstrual symptoms and comparing it with females having no premenstrual symptoms. Materials and Methods: BAEP was conducted on 60 females age group of 18–40 years in two groups in Research laboratory, Department of Physiology, Lala Lajpat Rai Memorial Medical College in collaboration with SVBP Hospital, Meerut for 6 months. The subjects were divided into two groups, Group A having premenstrual symptoms and Group B having no premenstrual symptoms. The test was conducted in later part of luteal phase 23rd–25th day of menstrual cycle. The absolute latencies (ALs) and interpeak latencies (IPLs) were the parameters measured for the analysis of BAEP. Results: IPL, that is, interpeak latencies I–III and III–V in age group 18–25 years, showed statistically significant decrease in luteal phase in females having premenstrual syndrome (PMS) as compared to normal cycling females. Conclusion: Premenstrual symptoms females are showing few significant changes in auditory responses at mid brain level as recorded by BAEP study which can be due to the modulatory effect of female gonadal hormones progesterone and estrogen on neurotransmitters (serotonin, gamma-aminobutyric acid, and glutamate) in central nervous system.

Evaluation of the effect of myopia on visual evoked potential in medical students

Background: Visual evoked potentials (VEPs) are electrical potential differences recorded from the occipital lobe in response to different visual stimulus. In myopic individuals, there is blurring of the stimuli, causing defocusing which tends to affect the VEP parameters. Aim and Objective: The study was designed and done to evaluate the effect of various degrees of myopia on VEP in medical students of age 18–24 years. Materials and Methods: A total of 120 subjects were included in this study, consist of 60 individuals without having any refractive disorders and 60 individuals having various degree of myopia, that is, 22 subjects with mild myopia of <?3D, 26 subjects with moderate myopia of ?3 to ?6D, and 12 subjects with severe myopia of > ?6D. The study was approved by Ethical and Research Committee, Govt. Medical College, Patiala. Results: In the present study, mean values for P100 latency were significantly high in myopic group as than in control group. Furthermore, mean values for N75 latency were significantly high in the myopic group as compared to the control group and mean values for N145 latency were significantly high in the myopic group as compared to the control group for both the right and left eyes. Mean values for amplitude (N75-P100) was significantly lower for the myopic group as compared to the control group for both the left and right eyes. There is prolongation of latencies in myopic individuals as compared to the control and latencies increase with the increase in degree of myopia. Furthermore, there is decrease in the amplitude in myopic individuals and it decreases with the increase in degree of myopia. Conclusion: The mean values for latencies were found to be comparable and the mean values of latencies were found to be increasing with increase of degree of myopia. Probably, the reason behind this result may be the optical blurring of the stimulus which lead to defocusing, therefore causes the prolongation of latency. The mean values for amplitude were found to be comparable and the mean values of amplitude were found to be decreasing with increase of degree of myopia. Probably, the reason for our finding is that in a pattern reversal VEP, the amplitude relies on the visual system’s ability to determine the pattern and on the degree of retinal image focus.

Recording of motor and somatosensory evoked potential in an anaesthetised Wistar rat using digital polyrite system

Objectives: The aim of this article is to explain the detailed methodology to record Motor evoked potential (MEP) and somatosensory evoked potential (SSEP) in adult albino Wistar rat, male (200–250 g) which has not been defined previously. Materials and Methods: We have standardised recording of both MEP and SSEP in these rats under anaesthesia on ADI digital polyrite system. Results: Evoked potentials have been widely studied in spinal cord injured patients to estimate the degree of injury and to establish a predictive measure of functional recovery. MEPs and SSEPs, arising from the motor cortex or peripheral nerve and generated either by direct electrical stimulation or by transcranial magnetic stimulation, have been advocated as a reliable indicator of descending and ascending pathway integrity. In the rat brain, there is a physical overlap between the motor and somatosensory cortex. Hence, our objective was to identify the exact area for stimulation in the cortex where we could record maximum response with the application of minimum electrical stimulation. Conclusion: The recording of MEP and SSEP together provides a powerful neurological technique to monitor the tracts of the spinal cord.

Alteration in pattern reversal visual evoked potential in pediatric population with amblyopia and spherical refractive errors

Purpose: To study the effect of refractive errors on pattern visual evoked potential (VEP) recordings in the pediatric population. Methods: This cross?sectional observational study assessed 240 eyes of 120 participants attending the outpatient department of a tertiary care center in North India. Participants were between 8 and 18 years of age; 30 participants each were recruited into four groups, namely emmetropia, myopia, hypermetropia, and amblyopia. They were then subjected to pattern reversal VEP, with P?100 amplitude and latency recorded for each participant. Results: The emmetropic group in this study provided normal values of P?100 parameters, namely P?100 latency and P?100 amplitude with readings of 115.78 ± 10.19 ms and 11.11 ± 4.08 ?V, respectively. P?100 amplitude was significant compared to P?100 latency in detecting the presence or absence of a specific type of refractive error. It was found that there was a significant association between severity of myopia and P?100 latency (both unaided and aided) with P < 0.05. The severity of hypermetropia showed a significant association with P?100 amplitude (unaided) (P < 0.05). Receiver operating characteristics analysis revealed P?100 amplitude to be a good predictor of refractive error and the cut?offs were calculated. Conclusion: The P?100 parameters of the pediatric Indian population were comparatively higher than conventional values. P?100 latency seemed to better correlate with myopia, while hypermetropia correlated with P?100 amplitude. P?100 amplitude appears to be the most significant predictor of the presence of refractive error in an individual.

Brain stem auditory evoked potential response in neonates after recovery from hyperbilirubinemia: A neurophysiological approach to screening neuronal hearing loss

Objectives: Neonatal hyperbilirubinemia leads to neurological damages including encephalopathy and hearing loss. This study aimed to screen and evaluate the hearing loss in neonates after recovery from hyperbilirubinemia using the Brainstem evoked response audiometry (BERA) test. Materials and Methods: This cross-sectional comparative study was conducted in Physiology Department at Chitwan Medical College, Nepal. It included 20 age and sex-matched neonates recently recovered from hyperbilirubinemia and 20 normal healthy controls. The external acoustic canals of subjects were checked for any blockage or collapse before BERA testing. The BERA recordings were performed after the neonate’s natural sleep following a standard lab protocol explained by Taylor’s Evoked Potential in Clinical Testing. Results: The BERA wave latencies were delayed with a higher number of case group neonates I (IL-75%, IR-80%), III (IIIL-70%, III R-80%), and V (VL- 80%, VR-85%) than those of controls. The percentage of neonates with delayed interwave latencies was comparable between groups. The neonate’s hearing sensitivity assessed using the grades of hearing impairment by WHO revealed slight (threshold of hearing left ear [THL]-25% and threshold of hearing right ear [THR]-30%) and moderate (THL-40% and THR-35%) grades among cases whereas no impairment (THL-60% and THR-55%) in controls. The hearing thresholds were more in cases. Conclusion: The auditory pathway is highly sensitive to elevated serum bilirubin. BERA detects even a minute degree of hearing damage seen after complete treatment of hyperbilirubinemia. Therefore, BERA is a helpful tool in the early screening of hearing impairment in neonates. This improves prognosis by early management so that the neurosensory systems develop to their full extent and one can enjoy a normal social life.

Relationship between optical coherence tomography angiography and visual evoked potential in patients with multiple sclerosis

Purpose: This study aimed to identify an easy?to?apply biomarker by correlating visual evoked potential (VEP) with optical coherence tomography angiography (OCTA) results in multiple sclerosis (MS). Methods: Our study was planned prospectively. Patients with MS were divided into two groups, VEP prolonged group 1 and VEP normal group 2. Age?matched and gender?matched healthy individuals (group 3) were included as the control group. Vascular density (VD) of the optic nerve head (ONH) and radial peripapillary capillaries (RPCs) were measured and recorded by OCTA. The optic nerve damage of patients was measured and recorded with a VEP device. Results: Thirty?two eyes were included in group 1, 50 eyes were included in group 2, and 51 healthy eyes were included in group 3. In terms of visual acuity, group 1 was significantly lower than the other groups (P < 0.001). Regardless of the prolongation of p100 latency in patients with MS, whole image, inside disc ONH VD and in the same sectors in RPC VD were found to be significantly lower than the control group (P < 0.05). Retinal nerve fiber layer thickness was found to be significantly lower in group 1 than in group 2 and group 3 (P < 0.05). There was a significant correlation between low ONH VD and RPC VD and prolonged VEP P100 (P < 0.05). Conclusion: VEP measurements can be correlated with OCTA measurements in patients with MS and can be used as a biomarker to determine the degree of optic nerve damage

Study of visual evoked potentials in asymptomatic HIV-positive persons

Background: Visual Evoked Potentials (VEPs) was studied in asymptomatic Human Immunodeficiency Virus (HIV) positive persons and corresponding controls to detect subclinical visual system involvement in the early stage of HIV. Aim and Objectives: To study VEPs in asymptomatic HIV-positive persons and corresponding controls. Materials and Methods: In this study,100 participants in the age group 25–45 years were recruited, fifty were HIV positive and asymptomatic (CD4 count >350 cells/mm3) and were not on Anti-Retroviral Treatment, and 50 were healthy age-matched individuals who were HIV negative. Results: P 100 latency was significantly prolonged in the study group than in the control group. No significant difference was observed between the control group and study group for the amplitude of VEP. Conclusion: Study of VEPs in asymptomatic HIV positive persons suggests subclinical visual nervous system involvement in early stages of HIV, as evidenced by prolonged P 100 latency. Hence, VEPs is important to detect subclinical nervous system involvement in the early stages of HIV.