Effect of different stimulus configurations on the visual evoked potential (VEP)

Abstract

The purpose of this study was to assess changes in the response profile of the pattern visual evoked potential (VEP) using three stimulus configurations simulating visual-field scotomas: central circular and central blank fields increasing incrementally in diameter from 1° to 15°, hemi-field, and quadrant patterns. Five visually normal adult subjects (ages 22-68 years) were tested binocularly at 1 m for each stimulus configuration on 5 separate days. A checkerboard test pattern (64 × 64 black-and-white checks, 85% contrast, 64 cd/m(2) luminance, 20 s of stimulus duration, 2-Hz temporal frequency) was used. The group mean VEP amplitude increased in a linear manner with increase in the central circular diameter (y = 0.805x + 2.00; r = 0.986) and decrease in central blank field diameter (y = -0.769x + 16.22; r = 0.987). There was no significant change in latency in nearly all cases. The group mean coefficient of variability results indicated that the VEP amplitude was repeatable for the different stimulus configurations. The finding of VEP response linearity for the circular stimulus fields, and repeatability for all stimulus configurations, suggests that the clinician may be able to use the VEP technique with the suggested test patterns as a rapid and simple tool for objective assessment for several types of visual-field defects for a range of abnormal visual conditions and special populations.

Optimization of the pattern visual evoked potential (VEP) in the visually-normal and mild traumatic brain injury (mTBI) populations

“…The VEP is an objective, rapid, repeatable, and non-invasive method to assess functionality and integrity of the retinal and earlyafferent, visuo-cortical pathways [1,2]. It has been used clinically since at least 1970 [3].…”

Objective assessment of visual attention in mild traumatic brain injury (mTBI) using visual-evoked potentials (VEP)

“…In addition, three correlations were performed: between each subject's ASRS Part A score and their alpha AR, between each subject's VSAT percentile score and their alpha AR and between each subject's ASRS and VSAT scores. Lastly, the coefficient of variation (CV ¼ standard deviation 7 mean) of the alpha wave responses was calculated to assess repeatability [28,29,45,53]. GraphPad Prism 5 software was used to perform the analyses.…”

“…amplitude and latency) [19,45,46] and alpha band (8-13 Hz) power [28,29,40]. This system was used to generate an alternating checkerboard stimulus pattern, record the cortical responses and analyse the data.…”

“…active, reference and ground) (Grass Technologies, Astro-Med, Inc., West Warwick, RI), each 1 cm in diameter [19,28,29,40,45,46]. The active, reference and ground electrodes were placed at the Oz, Fz, and Fp2 scalp positions, respectively.…”

Objective Assessment of Eye Dominance Using the VEP

“…This check size optimally stimulates the cumulative cone population, and thus produces maximal responsivity and repeatability. 33 The checkerboard pattern had a Michelson contrast of 85% and a mean luminance of 74 cd/m 2 . For each trial, the checkerboard pattern had a temporal frequency of 1 Hz (2 reversals per second).…”