Transient Visual Evoked Potentials Research Articles

Visual cortical area contributions to the transient, multifocal and steady-state VEP: A forward model-informed analysis

Abstract Central to our understanding of how visual-evoked potentials (VEPs) contribute to visual processing is the question of where their anatomical sources are. Three well-established measures of low-level visual cortical activity are widely used: the first component (“C1”) of the transient and multifocal VEP, and the steady-state VEP (SSVEP). Although primary visual cortex (V1) activity has often been implicated in the generation of all three signals, their dominant sources remain uncertain due to the limited resolution and methodological heterogeneity of source modelling. Here, we provide the first characterisation of all three signals in one analytic framework centred on the “cruciform model”, which describes how scalp topographies of V1 activity vary with stimulus location due to the retinotopy and unique folding pattern of V1. We measured the transient C1, multifocal C1, and SSVEPs driven by an 18.75 Hz and 7.5 Hz flicker, and regressed them against forward models of areas V1, V2, and V3 generated from the Benson-2014 retinotopy atlas. The topographic variations of all four VEP signals across the visual field were better captured by V1 models, explaining between 2 and 6 times more variance than V2/V3. Models with all three visual areas improved fit further, but complementary analyses of temporal dynamics across all three signals indicated that the bulk of extrastriate contributions occur considerably later than V1. Overall, our data support the use of peak C1 amplitude and SSVEPs to probe V1 activity, although the SSVEP contains stronger extrastriate contributions. Moreover, we provide elaborated heuristics to distinguish visual areas in VEP data based on signal lateralisation as well as polarity inversion.

Patterned edge-illuminated display for clinical examination of visual evoked potentials using simultaneous magnetic resonance imaging

PurposeCommonly used technologies for visual pattern stimulation cannot operate in a magnetic resonance imaging room because they can interfere with the operation of the scanner and are vulnerable to its electromagnetic and magnetic fields. The aim of this single-center prospective observational study was to introduce a novel, structurally uncomplicated, easy-to-maintain, patterned edge-illuminated display (PEID) device for visual pattern-reversal stimulation, compare it with a commonly used cathode ray tube screen, and verify the equivalence of quantitative assays. Materials and methodsThe left and right eyes of 36 healthy participants with undilated pupils were examined on a commercial visual evoked potential (VEP) apparatus and on the PEID device, where pattern-reversal transient VEPs were elicited by checkerboard stimuli with large (0.89°; 0.86°–0.92°) and small (0.21°; 0.20°–0.23°) checks. ResultsThe PEID device demonstrated the required reliability and dynamic characteristics, as well as precise time-locking required for a VEP diagnosis. The results of Deming's correlation analysis showed that both the commercial cathode ray tube monitor and the PEID device produced identical VEP results within the context of experimental uncertainty. The standard deviation of Deming's regression may indicate the uncertainty of the VEPs measured in clinical practice. The Bland-Altman analysis of the mean showed no significant difference in the amplitude and peak time of VEPs measured on the PEID device compared to that of the commercial cathode ray tube monitor. ConclusionsThe presented PEID device meets all the required standards and can be easily installed in various types of commercial magnetic resonance imaging scanners.

Is the prolongation latency of visual evoked potentials a pathological sign in children with Down’s syndrome without ocular abnormalities? Case–control study of children with Down’s syndrome

ObjectiveTo evaluate retino-cortical function in children with Down’s syndrome (DS) and no evident ocular abnormalities beyond mild refractive error, by recording visual evoked potentials (VEP) in response to pattern-reversal stimuli...

Temporal frequency dependence of the polarity inversion between upper and lower visual field in the pattern-onset steady-state visual evoked potential

PurposeAccording to the cruciform model, the upper and lower halves of the visual field representation in the primary visual cortex are located mainly on the opposite sides of the calcarine sulcus. Such a shape would have consequences for the surface-recorded visual evoked potential (VEP), as V1 responses to stimulation of the upper and lower hemifield manifest with opposite polarity (i.e., polarity inversion). However, the steady-state VEP results from a complex superposition of response components from different cortical sources, which can obscure the inversion of polarity. The present study assesses the issue for different stimulation frequencies which result in different patterns of superposition in the steady-state response.MethodsSequences of brief pattern-onset stimuli were presented at different stimulation rates ranging from 2 Hz (transient VEP) to 13 Hz (steady-state VEP). The upper and lower hemifields were tested separately and simultaneously. The data were assessed both in the time domain and in the frequency domain.ResultsComparing the responses to the stimulation of upper and lower hemifield, polarity inversion was present within a limited time interval following individual stimulus onsets. With increasing frequency, this resulted in an approximate inversion of the full steady-state response and consequently in a phase shift of approximately 180° in the time-domain response. Polarity inversion was more prominent at electrode Pz, also for transient responses. Our data also demonstrated that the sum of the hemifield responses is a good approximation of the full-field response.ConclusionWhile the basic phenomenon of polarity inversion occurs irrespective of the stimulus frequency, its relative impact on the steady-state response as a whole is the largest for high stimulation rates. We propose that this is because longer-lasting response components from other visual areas are not well represented in the steady-state VEP at higher frequencies.

Visual Evoked Potential Abnormalities in Phelan-McDermid Syndrome.

The current study used visual evoked potentials (VEPs) to examine excitatory and inhibitory postsynaptic activity in children with Phelan-McDermid syndrome (PMS) and the association with genetic factors. PMS is caused by haploinsufficiency of SHANK3 on chromosome 22 and represents a common single-gene cause of autism spectrum disorder (ASD) and intellectual disability. Transient VEPs were obtained from 175 children, including 31 with PMS, 79 with idiopathic ASD, 45 typically developing controls, and 20 unaffected siblings of children with PMS. Stimuli included standard and short-duration contrast-reversing checkerboard conditions, and the reliability between these 2 conditions was assessed. Test-retest reliability and correlations with deletion size were explored in the group with PMS. Children with PMS and, to a lesser extent, those with idiopathic ASD displayed significantly smaller amplitudes and decreased beta and gamma band activity relative to TD controls and PMS siblings. Across groups, high intraclass correlation coefficients were obtained between standard and short-duration conditions. In children with PMS, test-retest reliability was strong. Deletion size was significantly correlated with P60-N75 amplitude for both conditions. Children with PMS displayed distinct transient VEP waveform abnormalities in both time and frequency domains that might reflect underlying glutamatergic deficits that were associated with deletion size. A similar response pattern was observed in a subset of children with idiopathic ASD. VEPs offer a noninvasive measure of excitatory and inhibitory neurotransmission that holds promise for stratification and surrogate endpoints in ongoing clinical trials in PMS and ASD.

The clinical application of intraoperative visual evoked potential in recurrent craniopharyngiomas resected by extended endoscopic endonasal surgery

ObjectiveThe protection of visual function is a major challenge for recurrent craniopharyngioma due to the interface between tumor and surrounding structure (esp. optic nerve) is more unclear. Intraoperative visual evoked potential (VEP) has been integrated into transsphenoidal surgery for pituitary adenomas and primary craniopharyngiomas in the prediction of postoperative visual outcome. In the present study, we firstly analyzed the clinical value of the VEP in the prediction of postoperative visual outcome for recurrent craniopharyngiomas by extended endoscopic endonasal surgery (EEES). MethodsThirty-six patients with recurrent craniopharyngiomas who underwent EEES with intraoperative VEP monitoring were retrospectively reviewed. The association between the changes in the VEP amplitude and postoperative visual outcome was determined. In addition, other potential prognostic factors with regard to postoperative visual outcomes were also included in the analysis. ResultsGross total resection (GTR) was achieved in 32 patients (88.9%). Reproducible and stable VEP was recorded in 72 eyes. We recorded that there were 29 eyes remained stable VEP amplitude intraoperation, 4 (13.8%) of which suffered new visual acuity (VA) and 5 (17.2%) suffered new visual field (VF) defects after surgery. A transient VEP decrease was recorded in 41 eyes, 8 (19.5%) of which suffered from visual deterioration. Of 2 eyes with a permanent VEP decrease, 2 (100%) experienced postoperative visual impairment. Clinical variable analyses revealed a significant correlation between recurrent craniopharyngioma and age, adhesion with optic nerve, postoperative VA, and intraoperative VEP amplitude. Unstable VEP amplitude during operation and tight adhesion were independent risk factors for postoperative VA. Tight adhesion and a larger tumor volume were independent risk factors for postoperative VF defects. ConclusionsEEES provides a unique view for the lesions under and behind the chiasm and achieve higher rates of GTR with improved visual outcomes. Tight adhesion and unstable VEP amplitude were strong predictors of postoperative visual impairment. Recurrent craniopharyngiomas are more likely to adhere to the optic nerve, VEP is more likely to be unstable during operation, and the improvement rate of postoperative visual function is lower than primary craniopharyngiomas. So intraoperative VEP is more necessary for recurrent craniopharyngiomas.

The predictive value of intraoperative visual evoked potential for visual outcome after extended endoscopic endonasal surgery for adult craniopharyngioma.

Due to the proximity of craniopharyngioma to the optic apparatus, one of the most common complications after surgery is visual deterioration. Intraoperative visual evoked potential (VEP), as a means of real-time visual function monitoring, has been integrated into transsphenoidal surgery for pituitary adenoma to predict postoperative visual outcome. Compared with pituitary tumor, craniopharyngioma often adheres to optic nerves, with increased risk of postoperative visual impairment. Furthermore, extended endoscopic endonasal surgery (EEES) can provide direct visualization of the surgical plane between the craniopharyngioma and the optic nerves, which contributes to analysis of the mechanism of real-time VEP changes during surgery. Therefore, VEP monitoring applied during EEES for craniopharyngioma may have more clinical value. However, only 9 patients who underwent EEES with VEP monitoring for craniopharyngioma have been sporadically reported to date. In this paper, the authors present the largest series to date analyzing the clinical value of VEP to predict postoperative visual outcome in adult patients with craniopharyngioma. Sixty-five adult patients who underwent EEES with intraoperative VEP monitoring for primary craniopharyngioma were retrospectively reviewed. The association between changes in VEP amplitude and postoperative visual outcome was determined. In addition, other potential prognostic factors with regard to postoperative visual outcomes were included in the analysis. Gross-total resection was achieved in 59 patients (90.8%). Reproducible and stable VEP was recorded in 128 of 130 eyes (98.5%). During surgery, VEP remained stable in 108 eyes, 10 (9.3%) of which had new visual acuity (VA) and/or visual field (VF) defects after surgery. Transient VEP decrease was recorded in 15 eyes, 4 (26.7%) of which had visual deterioration. Of the 5 eyes with permanent VEP decrease, 3 (60%) experienced postoperative visual impairment. Permanent VEP decrease (OR 19.868, p = 0.007) and tight adhesion (OR 6.104, p = 0.040) were independent adverse factors for postoperative VA deterioration. Tight adhesion (OR 7.150, p = 0.002) and larger tumor volume (OR 1.066, p = 0.001) were significant risk factors for postoperative VF defects. Intraoperative VEP monitoring can serve as a real-time warning to guide surgeons to avoid postoperative visual impairment. It effectively predicted VA changes in adult patients with craniopharyngioma after EEES. Tight adhesion and larger tumor volume were also strong predictors of postoperative visual impairment.

Which Comes First in Sports Vision Training: The Software or the Hardware Update? Utility of Electrophysiological Measures in Monitoring Specialized Visual Training in Youth Athletes.

In the present study we combined popular methods of sports vision training (SVT) with traditional oculomotor protocols of Optometric Vision Therapy (OVT) and electrophysiological indexes of EEG and VEP activity to monitor training progress and changes in performance of youth ice hockey players without the history of concussion. We hypothesized that administration of OVT protocols before SVT training may result in larger performance improvements compared to the reverse order due to the initial strengthening of visual hardware capable of handling greater demands during training of visuomotor integration and information processing skills (visual software). In a cross-over design 53 youth ice hockey players (ages 13–18) were randomly assigned to one of the two training groups. Group one (hardware-software group) completed 5 weeks of oculomotor training first followed by 5 weeks of software training. For group 2 (software-hardware) the order of procedures were reversed. After 10 weeks of training both groups significantly improved their performance on all but one measure of the Nike/Senaptec Sensory station measures. Additionally, the software-hardware training order resulted in significantly lower frontal theta-to-gamma amplitude ratios on the Nike/Senaptec test of Near-Far Quickness as well as in faster P100 latencies. Both training orders also resulted in significant decreases in post-treatment P100 amplitude to transient VEP stimuli as well as decreased theta-gamma ratios for perception span, Go/No-Go and Hand Reaction time. The observed changes in the electrophysiological indexes in the present study are thought to reflect greater efficiency in visual information processing and cognitive resource allocation following 10 weeks of visual training. There is also some evidence of the greater effectiveness of the software-hardware training order possibly due to the improved preparedness of the oculomotor system in the youth athletes for administration of targeted protocols of the Optometric Vision Therapy.

Waveform feature extraction and signal recovery in single-channel TVEP based on Fitzhugh–Nagumo stochastic resonance

Objective. Transient visual evoked potential (TVEP) can reflect the condition of the visual pathway and has been widely used in brain–computer interface. TVEP signals are typically obtained by averaging the time-locked brain responses across dozens or even hundreds of stimulations, in order to remove different kinds of interferences. However, this procedure increases the time needed to detect the brain status in realistic applications. Meanwhile, long repeated stimuli can vary the evoked potentials and discomfort the subjects. Therefore, a novel unsupervised framework was developed in this study to realize the fast extraction of single-channel TVEP signals with a high signal-to-noise ratio. Approach. Using the principle of nonlinear aperiodic FitzHugh–Nagumo (FHN) model, a fast extraction and signal restoration technology of TVEP waveform based on FHN stochastic resonance is proposed to achieve high-quality acquisition of signal features with less average times. Results: A synergistic effect produced by noise, aperiodic signal and nonlinear system can force the energy of noise to be transferred into TVEP and hence amplifying the useful P100 feature while suppressing multi-scale noise. Significance. Compared with the conventional average and average-singular spectrum analysis-independent component analysis(average-SSA-ICA) method, the average-FHN method has a shorter stimulation time which can greatly improve the comfort of patients in clinical TVEP detection and a better performance of TVEP waveform i.e. a higher accuracy of P100 latency. The FHN recovery method is not only highly correlated with the original signal, but also can better highlight the P100 amplitude, which has high clinical application value.

Offset characteristic of transient and steady‐state flash visual evoked potentials

PurposeIn ISCEV flash stimulations, the brief stimuli onset time results in an overlap of the onset and offset response in the recorded visual evoked potential (VEP). However, the influence of a prolonged onset time in flash stimulation has not been studied yet. The aim of our study was to investigate the effect of the onset time on the transient and steady‐state VEP.MethodsWe studied 8 healthy subjects (3 m, 26 ± 3.6 years) using flash stimuli (d = 10°, luminance = 350 cd/m2, contrast = 99%). For transient stimulations, stimuli were presented with an onset time of 16 ms, 34 ms, 67 ms, and 200 ms at 1Hz for 180 sweeps. The amplitudes and latencies of P2 and P3 peaks were used for analysis. For steady‐state stimulations, stimuli were presented with an onset time of 16 ms, 33 ms, and 67 ms at 7.5 Hz for 5 sweeps with 30 cycles each. The amplitudes at 7.5Hz and the ratio of the amplitudes at 7.5 Hz and 15 Hz were evaluated. VEPs were recorded using electrodes at Oz (active), FCz (reference) and FPz (ground). For statistical analysis, Friedman's test and Wilcoxon Post‐Hoc tests (α = 0.05) were used.ResultsFor transient stimulations, significant differences (p = 0.000*) were found for latencies of the P3 peaks (median: 201 ms, 216 ms, 230 ms, 319 ms; p*16/67 = 0.0078, p*16/200 = 0.0078, p*33/200 = 0.0078, p*67/200 = 0.0078). The P2 peak amplitude (17.6 µV, 18.1 µV, 16.6 µV, 16.2 µV; p = 0.3476), P3 peak amplitude (5.1 µV, 3.4 µV, 5.3 µV, 8.0 µV; p = 0.0917) and P2 peak latency (103 ms, 105 ms, 106 ms, 104 ms; p = 0.2453) showed no significant differences. For steady‐state stimulations, no significant differences were found for amplitudes at stimulation frequency (2.0 µV/Hz, 1.5 µV/Hz, 1.1 µV/Hz; p = 0.197) and amplitude ratio (0.5, 0.6, 0.3; p = 0.093).ConclusionsA prolonged onset time leads to a significant increase of the P3 peak latency in transient VEP. No significant influence of the onset time was found for steady‐state VEP. Thus, the steady‐state VEP seems to be dominated by the onset response of the flash stimulation.

Design of an Online Brain-Computer Interface System Based on Field Programmable Gate Array

In the article, an online brain-computer interface (BCI) demo system based on Field Programmable Gate Array (FPGA) was designed. A colour visual stimulator based on a Video Graphics Array (VGA) monitor controlled by FPGA is designed to produce transient visual stimulations. An electroencephalography (EEG) acquisition module including active electrodes and driven-right-leg circuit is used to acquire the visual evoked potential (VEP) signal; Finite impulse response (FIR) filtering combined with an averaging method allows for extraction of the weak VEP signals. The template matching method is used in target identification. The FPGA is successfully used in the BCI system to complete multiple tasks such as the VGA controller, analog to digital (AD) converter controller, VEP signal processor and electronic device controller. Experiments show that the subjects’ transient VEP can successfully activate the electronic devices by the online BCI system which has relatively high identification accuracy. All these results show that the real time BCI demo system based on FPGA is feasible and effective.

Recognising the threat of vision loss in people living with HIV on antiretroviral therapy without retinitis

Background: People living with HIV (PLHIV) on antiretroviral therapy (ART) without retinitis may not have a healthy retinal structure. Aim: To examine the impact of the virus together with the ART medication in PLHIV without retinitis. Methods: This review used the following databases: PubMed, Google Scholar and EBSCOhost. Search terms included: HIV and/or retinal nerve fibre layer (RNFL); perimetry; colour vision; contrast sensitivity (CS); visual evoked potentials (VEPs); electroretinograms (ERGs); and the brain. All peer-reviewed studies related to PLHIV on ART without retinitis, up until September 2019, were included. Results: The mean RNFL thickness, and superior and inferior zones showed thinning. Affected visual functions include transient pattern VEP and ERG; contrast sensitivity; reduced total error scores on colour vision evaluation; and reduced mean deviation and pattern standard deviations on perimetry. Studies also showed concurrent thinning of the peripapillary retinal nerve fibre layer (ppRNFL) and perimetry, contrast sensitivity and colour vision. All these significant observations were seen at a cluster of differentiation 4 (CD4) count of less than 200 cells/mm 3 in PLHIV on ART with no retinitis. Further to this, studies have also related the retina to grey and white matter changes in PLHIV in the era of ART. A gap in research involves studies on the vascular impact of ART on the retina, which should be factored into studies going forward when studying PLHIV on ART. Conclusion: The decrease in visual function, the RNFL changes and neuro-ophthalmic involvement in PLHIV allow us to recognise the threat to vision loss when factoring in the expected longer lifespan that PLHIV on ART are afforded today.

An idle state-detecting method based on transient visual evoked potentials for an asynchronous ERP-based BCI

BackgroundAn asynchronous brain-computer interface (BCI) allows subject to freely switch between the working state and the idle state, improving the subject’s comfort. However, using only the event-related potential (ERP) to detect these two states is difficult because of the small amplitude of the ERP. MethodOur previous study finds that an odd-ball paradigm could evoke transient visual evoked potentials (TSVEPs) simultaneously with ERPs. This study adopts the TSVEP and the ERP to detect the idle state in the design of an asynchronous TSVEP-ERP-based BCI (T-E BCI). The T-E BCI extracts time and frequency features from brain signals and uses a novel probability-based fisher linear discriminant analysis (P-FLDA) to combine the classification results of the ERP and the TSVEP. ResultTen subjects perform visual speller and video watching experiments, and their brain signals are measured under the working and idle states. The main results show that the T-E BCI achieves a higher accuracy than the ERP-based BCI when judging the subject’s intentions and the two states. The P-FLDA performs better than the FLDA in combining the classification results. ConclusionsThe study demonstrates that adding the TSVEP can substantially reduce the number of wrongly detected trials. The T-E BCI provides a new way of designing an asynchronous BCI without adding any additional visual stimuli, which makes the BCI more practical.

Research progression of visual evoked potential in glaucomatous visual function evaluation

Visual evoked potential (VEP) is often used for the objective evaluation for impairment of visual function. Although these VEP-related tests have good results in the assessment of glaucoma, their application as routine tests in the clinical diagnosis of glaucoma is limited due to the time consumption and easy interference by the environment and the reliance on the experience of the doctors. However, several new VEP detection modes have emerged in the past decade, such as short-duration transient VEP and isolated check VEP. Preliminary studies have shown that both of them have good diagnostic ability in glaucoma, and more studies on the clinical application of these latest technologies are conducive to further understanding of their value in the visual function evaluation and follow-up of glaucoma. (Chin J Ophthalmol, 2020, 56: 61-65).

A BCI Gaze Sensing Method Using Low Jitter Code Modulated VEP.

Visual evoked potentials (VEPs) are used in clinical applications in ophthalmology, neurology, and extensively in brain–computer interface (BCI) research. Many BCI implementations utilize steady-state VEP (SSVEP) and/or code modulated VEP (c-VEP) as inputs, in tandem with sophisticated methods to improve information transfer rates (ITR). There is a gap in knowledge regarding the adaptation dynamics and physiological generation mechanisms of the VEP response, and the relation of these factors with BCI performance. A simple, dual pattern display setup was used to evoke VEPs and to test signatures elicited by non-isochronic, non-singular, low jitter stimuli at the rates of 10, 32, 50, and 70 reversals per second (rps). Non-isochronic, low-jitter stimulation elicits quasi-steady-state VEPs (QSS-VEPs) that are utilized for the simultaneous generation of transient VEP and QSS-VEP. QSS-VEP is a special case of c-VEPs, and it is assumed that it shares similar generators of the SSVEPs. Eight subjects were recorded, and the performance of the overall system was analyzed using receiver operating characteristic (ROC) curves, accuracy plots, and ITRs. In summary, QSS-VEPs performed better than transient VEPs (TR-VEP). It was found that in general, 32 rps stimulation had the highest ROC area, accuracy, and ITRs. Moreover, QSS-VEPs were found to lead to higher accuracy by template matching compared to SSVEPs at 32 rps. To investigate the reasons behind this, adaptation dynamics of transient VEPs and QSS-VEPs at all four rates were analyzed and speculated.

Enhanced Plasticity of Human Evoked Potentials by Visual Noise During the Intervention of Steady-State Stimulation Based Brain-Computer Interface.

Neuroplasticity, also known as brain plasticity, is an inclusive term that covers the permanent changes in the brain during the course of an individual's life, and neuroplasticity can be broadly defined as the changes in function or structure of the brain in response to the external and/or internal influences. Long-term potentiation (LTP), a well-characterized form of functional synaptic plasticity, could be influenced by rapid-frequency stimulation (or “tetanus”) within in vivo human sensory pathways. Also, stochastic resonance (SR) has brought new insight into the field of visual processing for the study of neuroplasticity. In the present study, a brain-computer interface (BCI) intervention based on rapid and repetitive motion-reversal visual stimulation (i.e., a “tetanizing” stimulation) associated with spatiotemporal visual noise was implemented. The goal was to explore the possibility that the induction of LTP-like plasticity in the visual cortex may be enhanced by the SR formalism via changes in the amplitude of visual evoked potentials (VEPs) measured non-invasively from the scalp of healthy subjects. Changes in the absolute amplitude of P1 and N1 components of the transient VEPs during the initial presentation of the steady-state stimulation were used to evaluate the LTP-like plasticity between the non-noise and noise-tagged BCI interventions. We have shown that after adding a moderate visual noise to the rapid-frequency visual stimulation, the degree of the N1 negativity was potentiated following an ~40-min noise-tagged visual tetani. This finding demonstrated that the SR mechanism could enhance the plasticity-like changes in the human visual cortex.

Visual Evoked Potentials and Glaucoma.

Visual evoked potentials (VEP) can be used to assess the function of the visual system objectively. Research on VEP testing as a method of glaucoma evaluation has been performed for many years. Pattern VEP has shown good specificity and sensitivity in the detection of glaucoma in some studies, but other studies have not shown similar efficacy. Multifocal VEP can produce a topographical measure of glaucomatous damage and has been shown to be able to detect a similar number of defects in patients with glaucoma or ocular hypertension as compared with the visual field test. Despite promising data on these VEP test modalities in the assessment of glaucoma, multiple aspects of test administration make their routine use impractical in a clinical setting. New VEP testing modalities, such as short-duration transient VEP and isolated-check VEP, allow the test to be performed more quickly and easily. Further research on these more recent technologies may allow us to use VEP effectively in the diagnosis and management of glaucoma.

Short-duration transient visual evoked potentials and color reflectivity discretization analysis in glaucoma patients and suspects.

To evaluate the use of short-duration transient visual evoked potentials (VEP) and color reflectivity discretization analysis (CORDA) in glaucomatous eyes, eyes suspected of having glaucoma, and healthy eyes. The study included 136 eyes from 136 subjects: 49 eyes with glaucoma, 45 glaucoma suspect eyes, and 42 healthy eyes. Subjects underwent Humphrey visual field (VF) testing, VEP testing, as well as peripapillary retinal nerve fiber layer optical coherence tomography imaging studies with post-acquisition CORDA applied. Statistical analysis was performed using means and ranges, ANOVA, post-hoc comparisons using Turkey's adjustment, Fisher's Exact test, area under the curve, and Spearman correlation coefficients. Parameters from VEP and CORDA correlated significantly with VF mean deviation (MD) (P<0.05). In distinguishing glaucomatous eyes from controls, VEP demonstrated area under the curve (AUC) values of 0.64-0.75 for amplitude and 0.67-0.81 for latency. The CORDA HR1 parameter was highly discriminative for glaucomatous eyes vs controls (AUC=0.94). Significant correlations are found between MD and parameters of short-duration transient VEP and CORDA, diagnostic modalities which warrant further consideration in identifying glaucoma characteristics.

Atypical waveform morphology in schizophrenia-visual evoked potential as a promising endophenotype.

Background:Electrophysiological research has provided measures of dysfunction of visual pathway in schizophrenia through the use of visual evoked potential (VEP) as the neurophysiologic tool.Objective:The main objective of this study is to examine the morphology and topography of VEP responses in schizophrenic patients and to explore the potentiality of VEP as an endophenotype.Materials and Methods:The study included 20 patients of schizophrenia who were recruited from the outpatient and inpatient department of psychiatry of a tertiary care rural hospital. The patients were assessed by tools such as Positive and Negative Symptoms Assessment Scale and Clinical Global Impression Scale for Severity. Transient Pattern Reversal VEP recordings were taken using an Evoked Potential Recorder (RMS EMG EP MARK II), and it was a cross-sectional study.Results:The mean age of patients was 45.95 ± 10.14 years in the range of 35–60 years. Qualitative analysis of VEP waveforms in people with schizophrenia was performed. Abnormal waveform morphology was observed in 14/20 (70%) of the study population and all of them were the chronic and severe cases. Six out of 15 (40%) showed lack of differentiation of the evoked complex so that the three waves (negative–positive-negative [NPN] complex) could not be identified. In 5 of 15 (33.33%) VEP records, a distinct altered waveform with extinguished second negative component of NPN complex was obtained.Conclusion:Qualitative morphometric findings of this study in terms of pattern-reversal VEP waveform abnormalities emerged as a tool to provide evidence of relationship for emerging as first potential biomarker for diagnosing schizophrenia.

Transient型VEP解析手法を用いた脳波インタフェースにおける指標点灯間隔および輝度の変化を利用した多選択肢化の検討

Transient型VEP解析手法を用いた脳波インタフェースにおける指標点灯間隔および輝度の変化を利用した多選択肢化の検討