Visually evoked cortical potentials (VERs) to checkerboard stimulation were studied as a function of locus of retinal stimulation, check size, and relative distribution of response over the cortex. Pattern stimuli of checks subtending 7.5, 15, 30, and 60' of arc were presented to the upper, central, lower, and lower-peripheral visual field. Evoked responses were recorded simultaneously from scalp electrodes located approximately 5 cm to the right or left of a point 2.5 cm above the inion, and approximately 2.5, 7.5, and 12.5 cm above the inion. Results obtained from the four electrode locations illustrated the differential effect of visual field stimulation on VER waveform in relation to the topography of the visual cortex. When activity was recorded from electrodes near the inion, VERs decreased as retinal stimulation was moved from the central to the lower-peripheral visual field. Such results indicate only that neural activity in response to peripheral stimulation decreased in the cortical area concerned with macular activity and not that, in general, VERs are less to peripheral than central visual stimulation. Responses at electrodes placed anteriorly over the peripheral projection area increased in amplitude as stimulation was changed from the central to the peripheral visual field
