Abstract

Since the introduction of sine wave gratings in electrophysiology [Campbell and Green, J. Physiol. 181, 573 (1965)], properties of spatial visual processing have been investigated and expressed in terms of spatial frequency channels. Such channels have also been found in human psycho­physics, leading to models of spatial vision such as that of Wilson and Bergen [Vision Res. 19, 19 (1979)]. The physiological substrate of such models in man is unknown but is generally thought to be situated early along the visual pathway. To test the nature of spatial frequency processing in striate visual cortex in primates, visually evoked potentials were recorded subdurally in alert rhesus monkeys. Two-dimensional (checkerboard) stimuli, in which spatial frequency components could be modulated independently, were presented. Our data show that neuronal responses to modulation of one spatial frequency component are highly dependent on the presence of (stationary or modulated) components with spatial frequencies at intervals up to two octaves. These interactions occur both for transient and for steady-state stimuli and are mutual, although not symmetric. They can best be modeled as mutual adaptations of localized spatial filters; a few populations of such filters, with bandwidths of 1–2 octaves, could account for the data.

© 1986 Optical Society of America