Adaptation to global structure induces spatially remote distortions of perceived orientation

Abstract

Adapting neurons at early stages of cortical visual processing to an oriented grating pattern suppresses responses to nearby orientations, causing a shift in the population response to subsequently viewed stimuli and an illusory distortion of perceived orientation: the classic tilt aftereffect. Perception of stimuli that are presented at unadapted spatial locations or that have a substantially different spatial frequency to the adapting stimulus remains veridical however by virtue of the fact that they stimulate a population of neurons distinct to those affected by adaptation. Here, we demonstrate that adapting to complex visual patterns containing circular or radial structure induces distortions of perceived orientation with markedly different characteristics to those traditionally reported. These novel effects occur in remote, unadapted spatial regions and are immune to manipulations of spatial frequency, rendering them incompatible with direct orientation-specific adaptation in early visual cortex. Rather, our results are most readily explained by a recurrent network in which global form encoding mechanisms that combine orientation information across space actively inhibit the local orientation detectors over which they pool.