Source locations of pattern-specific components of human visual evoked potentials. I. Component of striate cortical origin

The measured distributions are compatible with the hypothesis that component C. I, but not C. II, originates in striate cortex, from surface negative cortical activity, and an additive relationship was demonstrated between the half-field and the constituent quadrant VEP distributions.

Abstract

A study was made of the transverse distributions of human scalprecorded potentials evoked by the brief presentation of a pattern into different regions of a continuously illuminated diffuse field. The first two components of these visual evoked potentials (VEPs), designated C.I. (latency 65–80 msec) and C. II (latency 90–110 msec), were both greatly influenced by the retinal location of the stimulus pattern. In an initial study of the VEP waveforms with 12 subjects, followed by a more detailed investigation of the distribution of the individual components in 4 subjects, the following results were found. These results indicate that C. I and C. II have spatially separate sources. Assuming a simple dipolar model based on the known retinotopic organization of the striate cortex, it is shown that the measured distributions are compatible with the hypothesis that component C. I, but not C. II, originates in striate cortex, from surface negative cortical activity.