Patterned distribution of immunoreactive astroglial processes in the striate (V1) cortex of new world monkeys

The possibility of a modular organization of non‐neuronal elements was analyzed in the opercular region of the striate neocortex in adult New World monkeys. For this purpose, and in order to follow possible correlations in the general organization of neuronal and astroglial elements, immunocytochemical procedures for Glial Fibrillary Acid Protein (GFAP) and Microtubule Associated Protein 2 (MAP‐2), in addition to cytochrome oxidase (COX) histochemistry, were applied to tangential and coronal sections and analyzed by using computer‐assisted procedures. Astroglial interlaminar processes stemming from superficial laminae did not traverse lamina IVA, and thus did not appear in deeper layers. Clearly definable interlaminar processes were predominantly concentrated in laminae II–III. A honeycomb‐ like lattice was observed in tangential sections, with a “cell” size distribution similar to the MAP‐2‐IR lattice, suggesting an intimate association with the pyramidal columns. Additionally, analysis of similar sections disclosed the periodic appearance of large patches with high density of interlaminar processes, indicating a nonhomogeneous distribution of GFAP‐IR processes in the striate cortex. COX “blobs” appeared frequently to coincide with areas expressing high density of GFAP‐IR elements. These findings add a new perspective to current concepts of astroglial organization in the striate cortex of primates and reveal the existence of a non‐neuronal modular organization in the primate striate cerebral cortex, and suggest that possible correlations between relative distributions of neuronal and astroglial elements should be further analyzed in cortical areas with a clear modular organization such as the striate cortex. GLIA 25:85–92, 1999. © 1999 Wiley‐Liss, Inc.