Spatio-temporal visually evoked scalp potentials in response to partial-field patterned stimulation.

Visually evoked scalp potentials (VESP) have been recorded at 40 electrode sites from each of 3 subjects. Pattern appearance/disappearance was used for whole field and partial field stimulation. The data are displayed as equipotential maps. The topographical features of the equipotential maps show periods of stable organization followed by periods of relatively rapid change. The structure of the maps changes in a consistent pattern with the region of the retina stimulated; the first peak fits well within the framework of the cruciform model of striate cortex. The first and second peaks of the VESP appear to be caused by independent neural generators. The work reported in this paper shows major agreement with other authors and reconciles some points of disagreement between them.