Document Type

Article

Embargo Period

7-1-1983

Publication Date

7-1-1983

Abstract

We used horseradish peroxidase (HRP) to orthogradely label afferent axons in macaque striate cortex. Of the 38 axons that we recovered, nine were recorded intracellularly before being filled with HRP. Light microscope and computer reconstructions of filled processes reveal highly stereotyped patterns of arborization and suggest that there are at least five discrete populations of lateral geniculate nucleus (LGN) afferent axon: (1) those to layer 4Cβ, which have extremely circumscribed, dense terminal fields (small branches of which occasionally intrude into 4Cα) but which have not been shown to project to other laminae; (2) afferents to layer 4A, which in some cases send fine ascending collaterals into layer 2-3 and which do not, apparently, send collaterals to other laminae; (3) afferents to layer 1, which are fine, extend over large distances horizontally, and send collaterals to layer 6A; (4) afferents to the lower two-thirds of layer 4Cα, which have few or no collaterals in layer 6; and (5) afferents to the upper half of layer 4Cα, which have arborizing collaterals in layer 6B. Of the nine axons that were recorded intracellularly, those with projections to layer 4Cβ (two axons) and to layer 1 (one axon) had color-selective properties, whereas those (six axons) which arborized in 4Cα all had transient, broad band and highly contrast-sensitive receptive fields. These properties are consistent with derivations from somata in the parvocellular and magnocellular divisions of the LGN, respectively. Afferents to 4Cα were found to cover approximately 6 times as much surface area as afferents to 4Cβ. The preterminal trunks of all axons were found to follow tortuous paths through the neuropil-paths that may derive from axon segregation during development. The wide ranging, patchy distributions of single afferents in 4Cα suggest that individual 4Cα axons supply more than one ocular dominance stripe. In one case where the terminal arborization of a 4Cα axon was mapped against the transneuronally determined pattern of ocular dominance, three separate patches of terminal boutons were indeed found to coincide with the bands of one eye.

Journal

Journal of Neuroscience

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