Field studies of monocularly evoked cerebral potentials in bitemporal hemianopsia

W A number of studies’-” have documented the fact that, in normal subjects, the visual evoked response (VER) may be of higher voltage over the cerebral hemisphere opposite the visual field in which the photic stimulus is situated. Bitemporal hemianopsia provides a clinical situation that offers an additional opportunity to assess the components affected and the extent of the variations caused by differential hemispheric inputs, since the central connections of the intact visual half-field of each eye project to the ipsilateral visual area. VER data in individual cases have been reported previously by Vaughan and Katztnan” and Lehmann and associates. A scalp-wide plotting technic has been used in the present study to define the spatial characteristics of each major component of the VER. It is shown that ( 1 ) the voltage maxima of several, but not all, components of the VER are maximal ipsilateral to the eye being stimulated, (2) the observed asymmetries involve late components, as well as early ones, and (3) successive components have distinctive areal distributions.