SPACING OF CYTOCHROME-OXIDASE BLOBS IN VISUAL-CORTEX OF NORMAL AND STRABISMIC MONKEYS

Some models of visual cortical development are based on the assumption that the tangential organization of V1 is not determined prior to vis ual experience. In these models, correlated binocular activity is a ke y element in the formation of visual cortical columns, and when the de gree of interocular correlation is reduced the models predict an incre ase in column spacing. To examine this prediction we measured the spac ing of columns, as defined by cytochrome oxidase (CO) blobs, in the vi sual cortex of monkeys whose binocular vision was either normal or dis rupted by a strabismus. The spatial distribution of blobs was examined in seven normal and five strabismic macaques. Tangential sections thr ough the upper layers of the visual cortex were stained to reveal the two-dimensional (2D) pattern of CO blobs. Each blob was localized and their center-to-center spacing, packing arrangement and density were c alculated using 2D nearest-neighbor spatial analyses. The mean center- to-center spacing of blobs (590 mu m for normally reared and 598 mu m for strabismic macaques) and the mean density of blobs (3.67 blobs/mm( 2) for normally reared and 3.45 blobs/mm(2) for strabismic macaques) w ere not significantly different. In addition, the 2D packing arrangeme nt of the blobs was not affected by strabismus. While it is clear that neural activity plays a key role in the elaboration and refinement of ocular dominance cortical modules, we conclude that it does not deter mine the spatial period of the pattern of CO blobs, This suggests that aspects of the neural circuitry underlying the columnar architecture of the visual cortex are established prenatally and its fundamental pe riodicity is not modifiable by experience.