Abstract
To understand binocular integration in the human brain, it is vital to have a clear description of how inputs serving each eye are united in the primary visual cortex. Hubel and Wiesel showed in the macaque that the axon terminals of cells in the lateral geniculate nucleus are not randomly distributed in layer 4C. Instead, they are clustered into alternating bands, called ocular dominance columns, serving either the right eye or the left eye. To label the ocular dominance columns in the human brain, the occipital lobes were obtained after death from six adult subjects with a history of monocular visual loss. Flatmounts were processed for cytochrome oxidase (CO) to reveal metabolic activity in V1 and V2. Mean V1 surface area was 2,643 mm2 (range 1986–3477 mm2). Ocular dominance columns were present in all cases, having a mean width of 863 µm. There were 78–126 column pairs along the V1 perimeter. Human column patterns were highly variable, but in at least one person they resembled a scaled-up version of macaque columns. CO patches in the upper layers were centered on ocular dominance columns in layer 4C, with one exception. In this individual, the columns in a local area resembled those present in the squirrel monkey, and no evidence was found for column/patch alignment. In every subject, the contralateral eye's blind spot was conspicuous as an oval region without ocular dominance columns. It provided a precise landmark for delineating the central 15° of the visual field. A mean of 53.1% of striate cortex was devoted to the representation of the central 15°. This fraction was less than the proportion of striate cortex allocated to the representation of the central 15° in the macaque. Within the central 15°, each eye occupied an equal territory. Beyond this eccentricity, the contralateral eye predominated, occupying 63% of the cortex. In one subject, monocular visual loss began at age 4 months, causing shrinkage of ocular dominance columns. In V2, which had a larger surface area than V1, CO stripes were present but could not be classified as thick or thin.
Supported by the National Eye Institute