Source locations of pattern-specific components of human visual evoked potentials. II. Component of extrastriate cortical origin

Experiments indicating that C.I and C.II are influenced differently by pattern pre-exposure provide supporting evidence for the separability of these components and suggest that they are produced in functionally different cortical regions.

Abstract

Further studies are reported on the influence of retinal stimulus location on the surface distributions of individual pattern-related VEP components. The following results were observed for stimulation of different central and annular regions of the upper and lower field in four subjects: These results again indicate that C.I and C.II have spatially separate sources. The longitudinal distributions of C.II are shown to conform with those of a simple dipolar model based on the retinotopic organization of the extrastriate cortex on the outer surfaces of the occipital lobes. Also, the longitudinal distributions of C.I appear consistent with its proposed striate cortical origin. Both C.I and C.II are thought to originate from surface negative cortical activity. Experiments indicating that C.I and C.II are influenced differently by pattern pre-exposure provide supporting evidence for the separability of these components and suggest that they are produced in functionally different cortical regions. The implications of this work are discussed.