Retinotopic organization within the cat's posterior suprasylvian sulcus and gyrus

The organization of extrastriate visual areas of the cat's posterior suprasylvian sulcus and gyrus was studied with electrophysiological mapping methods. Analysis of retinotopic organization confirmed the presence of dorsal lateral and ventral lateral suprasylvian (DLS, VLS) visual areas (Palmer et al., '78, J. Comp. Neurol. 177:237-256) and demonstrated new features of organization. Areas DLS and VLS occupy the upper two-thirds of the posterior suprasylvian sulcus, with DLS wholly confined to the upper bank and VLS straddling the sulcal fundus. Both areas contain a partial representation of the lower quadrant of the visual field. A narrow strip of visually responsive cortex (periauditory belt) was identified adjoining DLS on the posterior ectosylvian gyrus; its organization and extent were not explored in detail. The organization of the posterior suprasylvian areas (PS) (Updyke, '82, Soc. Neurosci. Abst. 8:810) was explored in detail. Area PS lies inferior to areas VLS and 21b in the lower third of the posterior suprasylvian sulcus and gyrus, extending onto the fusiform gyrus. PS contains a partial representation of the lower quadrant of the visual field. It shares a representation of horizontal meridian with area 21b and a representation of central gaze with area VLS. Analysis of the PS/20 border region indicates that the representation of the lower quadrant periphery is common to the borders of PS, 20a, and 20b rather than lying internal to areas 20a and 20b as suggested by Tusa and Palmer ('80, J. Comp. Neurol. 193:147-164).