Optimal conditions for multifocal VEP recording for normal Japanese population established by receiver operating characteristic analysis

Abstract

The purpose of this study was to establish optimal conditions for recording multifocal visual evoked potentials (mVEPs) in Japanese individuals, whose skull frame presumably differs from Caucasians. The scalp point that was extended from the calcarine fissure was identified using magnetic resonance imaging scans of 200 subjects. MVEPs were recorded from 56 individuals using three single channels and combinations of vertical and horizontal channels. Five electrodes were placed at the inion, 4cm above the inion, 2.5cm below the inion, 4cm to the left or 4cm to the right of the inion. The signal-to-noise ratio (SNR) was obtained by measuring the root-mean-square (RMS) amplitude of a signal window (45-150ms) from each of 60-local responses that was divided by the average of the 60 RMS amplitudes of the noise window (325-430ms). Receiver operating characteristic (ROC) analyses were performed based on the proportion of mVEP responses that exceeded a specific SNR criterion, calculated for both the signal window and the noise window. The position of the calcarine fissure relative to the inion was significantly lower than the value reported for Caucasians. The ROC analyses disclosed that bi-channel combinations (one vertical and one horizontal) had significantly better performance to discriminate signal from noise in 60-local mVEP responses compared to any single channel and performed similarly to the tri-channel combination. Two sets of perpendicular channels should be simultaneously used in recording mVEP responses from Japanese people, among whom skull frame characteristics differ from those observed in Caucasians.