The effects of monocular deprivation on cytochrome-oxidase (CO) expression were used to reveal ocular dominance columns in flatmounts of the striate cortex in macaque (Macaca fascicularis) and talapoin (Miopithecus talapoin) monkeys. This procedure allowed the first direct visualization of the complete pattern of ocular dominance bands in macaque monkeys, and less complete reconstructions in talapoin monkeys. In a second macaque monkey, the ocular dominance organization was revealed by injecting wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) into one eye.

The organization of ocular dominance columns in the macaque monkeys conforms to previous descriptions, but the flat-mounted hemispheres provide accurate details on (1) the arrangement of columns, (2) the orientation of the representation of the optic disc, and (3) the breakdown of the bands in the cortex between the optic disc and monocular representations into a pattern of dots activated by the ipsilateral eye and larger surrounds related to the contralateral eye.

Talapoin monkeys, the smallest of Old World monkeys, have sharply segregated ocular dominance bands. The columns in talapoins are narrower than those in macaques, so that even with less striate cortex than macaques, talapoins have more ocular dominance hypercolumns.