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Improved characterization of visual evoked potentials in multiple sclerosis by topographic analysis.

ABSTRACT: In multiple sclerosis (MS), the combination of visual, somatosensory and motor evoked potentials (EP) has been shown to be highly correlated with the Expanded Disability Severity Scale (EDSS) and to predict the disease course. In the present study, we explored whether the significance of the visual EP (VEP) can be improved with multichannel recordings (204 electrodes) and topographic analysis (tVEP). VEPs were analyzed in 83 MS patients (median EDSS 2.0; 52 % with history of optic neuritis; hON) and 47 healthy controls (HC). TVEP components were automatically defined on the basis of spatial similarity between the scalp potential fields (topographic maps) of single subjects' VEPs and reference maps generated from HC. Non-ambiguous measures of latency, amplitude and configuration were derived from the maps reflecting the P100 component. TVEP was compared to conventional analysis (cVEP) with respect to reliability in HC, validity using descriptors of logistic regression models, and sensitivity derived from receiver operating characteristics curves. In tVEP, reliability tended to be higher for measurement of amplitude (p = 0.06). Regression models on diagnosis (MS vs. HC) and hON were more favorable using tVEP- versus cVEP-predictors. Sensitivity was increased in tVEP versus cVEP: 72 % versus 60 % for diagnosis, and 88 % versus 77 % for hON. The advantage of tVEP was most pronounced in pathological VEPs, in which cVEPs were often ambiguous. TVEP is a reliable, valid, and sensitive method of objectively quantifying pathological VEP in particular. In combination with other EP modalities, tVEP may improve the monitoring of disease course in MS.

SUBMITTER: Hardmeier M

PROVIDER: S-EPMC3921459 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Evaluation of optic neuropathy in multiple sclerosis using low-contrast visual evoked potentials.

Project description:Contrast acuity (identification of low-contrast letters on a white background) is frequently reduced in patients with demyelinating optic neuropathy associated with multiple sclerosis (MS), even when high-contrast (Snellen) visual acuity is normal. Since visual evoked potentials (VEPs) induced with high-contrast pattern-reversal stimuli are typically increased in latency in demyelinating optic neuropathy, we asked if VEPs induced with low-contrast stimuli would be more prolonged and thus helpful in identifying demyelinating optic neuropathy in MS.We studied 15 patients with clinically definite MS and 15 age-matched normal controls. All subjects underwent a neuro-ophthalmologic assessment, including measurement of high-contrast visual acuity and low-contrast acuities with 25%, 10%, 5%, 2.5%, and 1.25% contrast Sloan charts. In patients with MS, peripapillary retinal nerve fiber layer (RNFL) thickness was determined using optical coherence tomography. Monocular VEPs were induced using pattern-reversal checkerboard stimuli with 100% and 10% contrast between checks, at 5 spatial frequencies (8-130 minutes of arc).VEP latencies were significantly increased in response to low- compared with high-contrast stimuli in both groups. VEP latencies were significantly greater in patients with MS than controls for both high- and low-contrast stimuli. VEP latencies correlated with high- and low-contrast visual acuities and RNFL thickness. VEPs were less likely to be induced with low- than with high-contrast stimuli in eyes with severe residual visual loss.Visual evoked potentials obtained in patients with multiple sclerosis using low-contrast stimuli are increased in latency or absent when compared with those obtained using high-contrast stimuli and, thus, may prove to be helpful in identifying demyelinating optic neuropathy.

| S-EPMC2788801 | biostudies-other

Retinotopic and topographic analyses with gaze restriction for steady-state visual evoked potentials.

Project description:Although the mechanisms of steady-state visual evoked potentials (SSVEPs) have been well studied, none of them have been implemented with strictly experimental conditions. Our objective was to create an ideal observer condition to exploit the features of SSVEPs. We present here an electroencephalographic (EEG) eye tracking experimental paradigm that provides biofeedback for gaze restriction during the visual stimulation. Specifically, we designed an EEG eye tracking synchronous data recording system for successful trial selection. Forty-six periodic flickers within a visual field of 11.5° were successively presented to evoke SSVEP responses, and online biofeedback based on an eye tracker was provided for gaze restriction. For eight participants, SSVEP responses in the visual field and topographic maps from full-brain EEG were plotted and analyzed. The experimental results indicated that the optimal visual flicking arrangement to boost SSVEPs should include the features of circular stimuli within a 4-6° spatial distance and increased stimulus area below the fixation point. These findings provide a basis for determining stimulus parameters for neural engineering studies, e.g. SSVEP-based brain-computer interface (BCI) designs. The proposed experimental paradigm could also provide a precise framework for future SSVEP-related studies.

| S-EPMC6418283 | biostudies-literature

Empirical mode decomposition processing to improve multifocal-visual-evoked-potential signal analysis in multiple sclerosis.

Project description:To study the performance of multifocal-visual-evoked-potential (mfVEP) signals filtered using empirical mode decomposition (EMD) in discriminating, based on amplitude, between control and multiple sclerosis (MS) patient groups, and to reduce variability in interocular latency in control subjects.MfVEP signals were obtained from controls, clinically definitive MS and MS-risk progression patients (radiologically isolated syndrome (RIS) and clinically isolated syndrome (CIS)). The conventional method of processing mfVEPs consists of using a 1-35 Hz bandpass frequency filter (XDFT). The EMD algorithm was used to decompose the XDFT signals into several intrinsic mode functions (IMFs). This signal processing was assessed by computing the amplitudes and latencies of the XDFT and IMF signals (XEMD). The amplitudes from the full visual field and from ring 5 (9.8-15° eccentricity) were studied. The discrimination index was calculated between controls and patients. Interocular latency values were computed from the XDFT and XEMD signals in a control database to study variability.Using the amplitude of the mfVEP signals filtered with EMD (XEMD) obtains higher discrimination index values than the conventional method when control, MS-risk progression (RIS and CIS) and MS subjects are studied. The lowest variability in interocular latency computations from the control patient database was obtained by comparing the XEMD signals with the XDFT signals. Even better results (amplitude discrimination and latency variability) were obtained in ring 5 (9.8-15° eccentricity of the visual field).Filtering mfVEP signals using the EMD algorithm will result in better identification of subjects at risk of developing MS and better accuracy in latency studies. This could be applied to assess visual cortex activity in MS diagnosis and evolution studies.

| S-EPMC5909914 | biostudies-literature

Delayed P100-Like Latencies in Multiple Sclerosis: A Preliminary Investigation Using Visual Evoked Spread Spectrum Analysis.

Project description:Conduction along the optic nerve is often slowed in multiple sclerosis (MS). This is typically assessed by measuring the latency of the P100 component of the Visual Evoked Potential (VEP) using electroencephalography. The Visual Evoked Spread Spectrum Analysis (VESPA) method, which involves modulating the contrast of a continuous visual stimulus over time, can produce a visually evoked response analogous to the P100 but with a higher signal-to-noise ratio and potentially higher sensitivity to individual differences in comparison to the VEP. The main objective of the study was to conduct a preliminary investigation into the utility of the VESPA method for probing and monitoring visual dysfunction in multiple sclerosis. The latencies and amplitudes of the P100-like VESPA component were compared between healthy controls and multiple sclerosis patients, and multiple sclerosis subgroups. The P100-like VESPA component activations were examined at baseline and over a 3-year period. The study included 43 multiple sclerosis patients (23 relapsing-remitting MS, 20 secondary-progressive MS) and 42 healthy controls who completed the VESPA at baseline. The follow-up sessions were conducted 12 months after baseline with 24 MS patients (15 relapsing-remitting MS, 9 secondary-progressive MS) and 23 controls, and again at 24 months post-baseline with 19 MS patients (13 relapsing-remitting MS, 6 secondary-progressive MS) and 14 controls. The results showed P100-like VESPA latencies to be delayed in multiple sclerosis compared to healthy controls over the 24-month period. Secondary-progressive MS patients had most pronounced delay in P100-like VESPA latency relative to relapsing-remitting MS and controls. There were no longitudinal P100-like VESPA response differences. These findings suggest that the VESPA method is a reproducible electrophysiological method that may have potential utility in the assessment of visual dysfunction in multiple sclerosis.

| S-EPMC4699709 | biostudies-literature

Correction: Empirical mode decomposition processing to improve multifocal-visual-evoked-potential signal analysis in multiple sclerosis.

Project description:[This corrects the article DOI: 10.1371/journal.pone.0194964.].

| S-EPMC5929517 | biostudies-literature

Decoding Steady-State Visual Evoked Potentials From Electrocorticography.

Project description:We report on a unique electrocorticography (ECoG) experiment in which Steady-State Visual Evoked Potentials (SSVEPs) to frequency- and phase-tagged stimuli were recorded from a large subdural grid covering the entire right occipital cortex of a human subject. The paradigm is popular in EEG-based Brain Computer Interfacing where selectable targets are encoded by different frequency- and/or phase-tagged stimuli. We compare the performance of two state-of-the-art SSVEP decoders on both ECoG- and scalp-recorded EEG signals, and show that ECoG-based decoding is more accurate for very short stimulation lengths (i.e., less than 1 s). Furthermore, whereas the accuracy of scalp-EEG decoding benefits from a multi-electrode approach, to address interfering EEG responses and noise, ECoG decoding enjoys only a marginal improvement as even a single electrode, placed over the posterior part of the primary visual cortex, seems to suffice. This study shows, for the first time, that EEG-based SSVEP decoders can in principle be applied to ECoG, and can be expected to yield faster decoding speeds using less electrodes.

| S-EPMC6168710 | biostudies-literature

Assessing amblyopia treatment using multifocal visual evoked potentials.

Project description:BackgroundTo evaluate the effect of occlusion treatment for anisometropic amblyopia using multifocal visual evoked potentials (mfVEPs).MethodsThe patients for this study comprised 19 patients (mean age 6.05?±?1.65 years) with anisometropic amblyopia underwent mfVEP analysis using the RETIscan® system before and after occlusion treatment. After dividing the area into six ring areas and four quadrants, we analyzed the amplitudes and latencies of the mfVEPs.ResultsThe amplitudes of ring 1 (central field) in amblyopic eyes after treatment were significantly higher than those in the other rings (p?=?0.001). The mfVEP amplitudes in each of the six rings between amblyopic eyes and fellow eyes at diagnosis and after occlusion treatment showed no significant differences. In quadrant 1 the amplitudes of the amblyopic eyes and fellow eyes were significantly different at the time of diagnosis (p?=?0.005), whereas after occlusion treatment there was no significant difference (p?=?0.888). The amplitudes for each of the six rings at diagnosis and after occlusion treatment in amblyopic eyes versus fellow eyes showed no significant difference. There were also no differences in the amplitudes in each of the four quadrants at the time of diagnosis and after occlusion treatment in amblyopic eyes versus fellow eyes. No significant difference was found in the comparison of latency values in each of the six rings or in each of the four quadrants at diagnosis and after occlusion treatment in amblyopic eyes versus their fellow eyes.ConclusionsThe amplitudes of quadrant 1 in amblyopic eyes compared with those of the fellow eyes at diagnosis were increased after occlusion treatment. Changes of the difference between amblyopic eyes and fellow eyes in quadrant 1 after occlusion treatment could be a useful, objective method for monitoring improvement in visual acuity.

| S-EPMC6090668 | biostudies-literature

Visual Evoked Potentials in Primary Open Angle Glaucoma.

Project description:Visual evoked potentials (VEPs) assess the integrity of the visual pathways from the optic nerve to the occipital cortex. Optic disc cupping and visual field loss have been associated with prolongation of latency of VEP in primary open angle glaucoma (POAG).Pattern reversal and flash VEP tests were done in consenting 20 primary open angle glaucoma eyes and 40 normal control eyes.In POAG cases, the refractive error [3.51 ± 1.88 versus 1.88 ± 1.11, D, p = 0.001], cup-disc ratio in percent [66.00 ± 16.98 versus 28.50 ± 5.80, p = 0.001], intraocular pressure [19.55 ± 2.08 versus 11.65 ± 1.64, mmHg, p = 0.001], and automated visual field pattern standard deviation [4.13 ± 6.96 versus 1.64 ± 0.45, dB, p = 0.001] were significantly more than in control. The visual acuity [0.41 ± 0.29 versus 1.00 ± 0.00, p = 0.001], foveal visual sensitivity [25.92 ± 6.88 versus 33.48 ± 1.75, dB, p = 0.001], and automated visual field mean deviation [-9.63 ± 10.58 versus 0.07 ± 1.54, dB, p = 0.001] were significantly less in cases than in control. Among VEP variables, pattern reversal latency N145 [149.00 ± 15.75 versus 137.52 ± 15.20, ms, p = 0.011], flash amplitude N75 [2.18 ± .57 versus 1.47 ± .38, μV, p = 0.001], and flash amplitude N145 [1.99 ± .39 versus 1.43 ± .38, μV, p = 0.001] were increased in cases. The pattern reversal amplitude N75 [1.97 ± .35 versus 2.47 ± .58, μV, p = 0.001], amplitude P100 [3.09 ± .46 versus 6.07 ± 1.44, μV, p = 0.001], and amplitude N145 [2.21 ± .58 versus 4.45 ± 1.99, μV, p = 0.001] were decreased in cases.POAG caused glaucomatous damage to optic pathway.

| S-EPMC5541795 | biostudies-other

Visual evoked potentials in succinate semialdehyde dehydrogenase (SSADH) deficiency.

Project description:In mammals, increased GABA in the central nervous system has been associated with abnormalities of visual evoked potentials (VEPs), predominantly manifested as increased latency of the major positive component P100. Accordingly, we hypothesized that patients with a defect in GABA metabolism, succinate semialdehyde dehydrogenase (SSADH) deficiency (in whom supraphysiological levels of GABA accumulate), would manifest VEP anomalies. We evaluated VEPs on two patients with confirmed SSADH deficiency. Whereas the P100 latencies and amplitudes for binocular VEP analyses were within normal ranges for both patients, the P100 latencies were markedly delayed for left eye (OS) (and right eye (OD), patient 1) and monocular OS (patient 2): 134-147 ms; normal <118 ms. We hypothesize that elevated GABA in ocular tissue of SSADH patients leads to a use-dependent downregulation of the major GABAergic receptor in eye, GABA(C), and that the VEP recordings' abnormalities, as evidenced by P100 latency and/or amplitude measurements, may be reflective of abnormalities within visual systems. This is a preliminary finding that may suggest the utility of performing VEP analysis in a larger sample of SSADH-deficient patients, and encourage a neurophysiological assessment of GABA(C) receptor function in Aldh5a1(-/-) mice to reveal new pathophysiological mechanisms of this rare disorder of GABA degradation.

| S-EPMC2888988 | biostudies-literature

Pattern visual evoked potentials elicited by organic electroluminescence screen.

Project description:PurposeTo determine whether organic electroluminescence (OLED) screens can be used as visual stimulators to elicit pattern-reversal visual evoked potentials (p-VEPs).MethodCheckerboard patterns were generated on a conventional cathode-ray tube (S710, Compaq Computer Co., USA) screen and on an OLED (17 inches, 320 × 230?mm, PVM-1741, Sony, Tokyo, Japan) screen. The time course of the luminance changes of each monitor was measured with a photodiode. The p-VEPs elicited by these two screens were recorded from 15 eyes of 9 healthy volunteers (22.0 ± 0.8 years).ResultsThe OLED screen had a constant time delay from the onset of the trigger signal to the start of the luminescence change. The delay during the reversal phase from black to white for the pattern was 1.0?msec on the cathode-ray tube (CRT) screen and 0.5?msec on the OLED screen. No significant differences in the amplitudes of P100 and the implicit times of N75 and P100 were observed in the p-VEPs elicited by the CRT and the OLED screens.ConclusionThe OLED screen can be used as a visual stimulator to elicit p-VEPs; however the time delay and the specific properties in the luminance change must be taken into account.

| S-EPMC4147363 | biostudies-literature

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