Anisotropy in the representation of direction preferences in cat area 18.

Higher visual cortical areas are involved in the perception of complex stimuli, such as the optic flow created by self-motion. On the other hand, area 18 is thought to extract primitive visual features, feeding higher cortical areas for further processing. In this study, we applied optical imaging of intrinsic signals in the central, lower visual field of cat area 18, and reconstructed direction preference and direction selectivity maps in each hemisphere. We observed a significant overrepresentation of downward and temporal directions, in accordance with previous electrophysiological results. Cardinal orientations were not overrepresented, however. Downward directions were overrepresented at the highest direction selectivity domains. Temporal direction representation, on the other hand, decreased with direction selectivity. Our findings therefore suggest the existence of a neural substrate for the processing of optic flow in cat area 18.