Distribution of pattern-evoked potentials in the facial area.

We studied the spatial distribution of the pattern-evoked potentials on the face with a simultaneous 16-channel recording system. The results showed that the responses had their first positive component at the peak latency of 52.0 +/- 1.9 (S.E.) msec. The maximum potential value within the equipotential maps was in the region around the stimulated eye in eight normal subjects. One patient with one enucleated eye showed the maximum value within the map only around the fellow eye; much later, at a peak latency of approximately 100 msec, we obtained a response with a maximum on the scalp around the inion. In another patient with long-standing optic nerve disease, the pattern-evoked potentials were absent but the flash-evoked potentials were normal, showing the maximum value in the region near the stimulated eye.