Thalamic inputs to cytochrome oxidase-rich regions in monkey visual cortex.

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Abstract
In primate primary visual cortex, staining for cytochrome oxidase reveals a regular array of blob-like structures, most prominent in layers II and III but also present in layers V and VI. In an attempt to learn more about the input to these blobs, the lateral geniculate bodies of macaques [Macaca fascicularis] and squirrel monkeys [Saimiri sciureus] were injected with [3H]proline or horseradish peroxidase [HRP]. The cortex was looked into for transported label. As expected, label was present in layers IVa, IVc.alpha., IVc.beta. and VI. Both methods revealed an array of puffs deep in layer III. Seen in tangential sections, the puffs precisely matched the cytochrome blobs. A projection from the lateral geniculate body to the blob regions deep in layer II/III is indicated, either indirect via layer IV or more likely direct. In area 18 stained for cytochrome oxidase, complex banding patterns were observed; these were remarkably similar to the pattern found after [3H]proline or HRP injection and were also similar to the pattern produced with 2-deoxyglucose labeling after stimulation with vertical or horizontal stripes; the proline and peroxidase labels probably represent a projection from the pulvinar to area 18.