Hemifield VEPs and Bilateral Cortical Representation of the Fovea

Ocular dependence of hemifield visual evoked potentials: Relevance to bilateral cortical representation of central vision

Jonathan D. Victor, Mary M. Conte and Costantino Iadecola

Clinical Vision Sciences 4, 261-276 (1991)

Summary

In primates there are cells in the nasal half of the fovea which project to the ipsilateral LGN, and from there presumably to the ipsilateral primary visual cortex (Leventhal et al., 1988; Science, 240, 66-67). Accordingly, the pattern of cortical activation produced by monocular vbiewing of a single hemifield should depend on the eye which is stimulated. We studied visual evoked potentials (VEPs) elicted by monocular hemifield stimulation in man to determine whether such interocular differences could be detected. Such a difference was indeed present, and (according to a resampling technique) was unlikely to be due to chance alone in 5 of 6 subjects. Dipole modeling showed that this difference was consistent with the pattern of retino-calcarine projections described in primates. We conclude that the bilateral cortical representation of the nasal half of foveal retina found in primates is likely to be present also in man. These results are discussed in relation to binocular vision near the vertical meridian.
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