Functional anatomy of the second visual area (V2) in the macaque.

To study the functional organization of secondary visual cortex (V2) in the primate, 14C-2-deoxy-d-glucose (DG) was injected while macaque monkeys were shown specific visual stimuli. Wherever possible, patterns of DG uptake were compared with the position of dark and light cytochrome oxidase (cytox) stripes (Tootell et al., 1983). Often, the DG effects of 2 different stimuli were compared in the same hemisphere to eliminate ambiguities inherent in between-animal comparisons. Data were obtained from a large number of animals in conjunction with related DG studies in area V1 (primary visual or striate cortex). The following conclusions were reached: (1) in some macaque monkeys, dark cytox stripes were faint or absent. Although this could conceivably be due to poor staining technique, some evidence suggests that the lack of enzyme stripe pattern is real. In all animals, including those that showed poor or no cytox staining evidence for stripes, the functional architecture revealed by the DG was consistently present and robust. (2) Uniform gray stimuli produce a relatively uniform pattern and minimal stimulus-related DG uptake. (3) Eye movements per se produce some uptake in the V2 stripes. (4) Very generalized visual stimulation conditions (e.g., binocular stimulation with a grating of varied orientation and varied spatial frequency) produced a pattern of uptake that is greatest in both sets of dark cytox stripes and lighter in the light cytochrome stripes. (5) In both the DG and cytox results, the V2 "stripes" are more accurately described as stripe-shaped collections of patches. (6) In almost all cases, DG patterns were columnar in shape, extending from white matter to cortical surface. The boundaries of the columns were most sharply defined, and the contrast was highest, in layers 3B/4, becoming slightly more blurry and lower in contrast in other layers. Laminar differences between DG patterns in V2 were almost negligible, compared with the profound laminar differences in macaque V1. (7) There is no DG evidence for, and much against, the possibility of an ocular dominance architecture in V2. (8) There are orientation columns in macaque V2. DG-labeled orientation columns are spaced further apart than those in V1, by a factor of about 1.6, but the columns are not correspondingly wider. (9) Spatially diffuse variations in color produce high uptake confined, at least largely, to the thin cytox stripes. (10) There is evidence for spatially antagonistic color surrounds in color cells in the thin stripes.(ABSTRACT TRUNCATED AT 400 WORDS)