Functional specialization in the lower and upper visual fields in humans: Its ecological origins and neurophysiological implications

Abstract

AbstractFunctional specialization in the lower and upper visual fields in humans is analyzed in relation to the origins of the primate visual system. Processing differences between the vertical hemifields are related to the distinction betweennear(peripersonal) andfar(extrapersonal) space, which are biased toward the lower and upper visual fields, respectively.Nonlinear/globalprocessing is required in the lower visual field in order to pergeive the optically degraded and diplopic images in near vision, whereas objects in far vision are searched for and recognized primarily usinglinear/localperceptual mechanisms. The functional differences between near and far visual space are correlated with their disproportionate representations in thedorsalandventraldivisions of visual association cortex, respectively, and in themagnocellularandparvocellularpathways that project to them. Advances in far visual capabilities and forelimb manipulatory skills may have led to a significant enhancement of these functional specializations.