IDENTIFICATION AND VISUOTOPIC ORGANIZATION OF AREAS PO AND POD IN CEBUS MONKEY

Two visual areas of the anterior bank of the parietooccipital sulcus, areas PO and POd, were identified and their visual field representatio ns were studied in six anesthetized and paralyzed Cebus monkeys. The d efinition of these areas was based on electrophysiological mapping and myeloarchitecture. PO is located in the ventral aspect of the anterio r bank of the parietooccipital sulcus and ventral precuneate gyrus. It borders area V2 posteriorly and ventrally in the depth of the parieto occipital sulcus, area V3d laterally, and another undescribed visual a rea medially. POd was located dorsal to area PO and ventral to archite ctonic area PE. The representations of the visual field in areas PO an d POd are complex. In each hemisphere, these areas have a virtually co mplete representation of the contralateral visual hemifield. Different from the previously described visual areas, in PO and POd there is a precise organization of isopolar lines and a complex organization of t he isoeccentric ones. In PO, as well as in POd, the representation of the horizontal meridian runs dorsoventrally along the parietooccipital sulcus. The upper visual quadrant is represented medially and the low er visual quadrant laterally. A large and complex representation of th e periphery, from 20 degrees to 60 degrees eccentricity is present at the lateral and medial portions of these areas. By contrast, the repre sentation of the central 20 degrees is very small in both PO and POd. The central visual field is represented ventrally in PO and dorsally i n area POd. Area POd shows a more stratified myeloarchitectonic patter n than PO and both areas can be distinguished from other surrounding a reas by their heavier myelinated pattern. (C) 1994 Wiley-Liss, Inc.