Termination of afferent axons in macaque striate cortex

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 intracelhrlarly 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 4Cp, which have extremely circumscribed, dense terminal fields (small branches of which occasionally intrude into 4Ca) 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 4Ca, which have few or no collaterals in layer 6; and (5) afferents to the upper half of layer 4Ca, which have arborizing collaterals in layer 6B. Of the nine axons that were recorded intracellularly, those with projections to layer 4Cp (two axons) and to layer 1 (one axon) had color-selective properties, whereas those (six axons) which arborized in 4Ca 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 4Ca were found to cover approximately 6 times as much surface area as afferents to 4Cp. 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 4C~u suggest that individual 4& axons supply more than one ocular dominance stripe. In one case where the terminal arborization of a 4Ca 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.The primate visual system is characterized by successive and discrete transformations in the neural representation of visual space. One such transformation occurs between the lateral geniculate nucleus (LGN) and cells in the thalamo-recipient laminae of striate cortex. Even though the receptive fields of cells in layer 4C-the layer that receives most of the LGN input-lack orientation selectivity and to some extent resemble those of the LGN, the transfer of information seems not to occur in

Context-sensitive binding by the laminar circuits of V1 and V2: A unified model of perceptual grouping, attention, and orientation contrast

“…V1layer 6 cells, :c;jb receive input from the LGN (Blasdel & Lund, 1983), which, as described above, is represented by the contrast-polarity pooled oriented input, Cijk· They also receive two types of folded-feedbnck excitation. The first type is intracortical feedback from above-threshold pyramidal cells in V1layer 2/3, Zijb as shown in Figure 6c Kisvarday et al, 1989).…”

Biological image motion processing: A review

“…Furthermore, it is known that such cells have well defined target sublaminae of striate cortex, terminating in layer IV C alpha (Blasdel and Lund, 1983) and that a major projection from this lamina goes (via layer IVB) to MT, an extrastriate area specialized for motion.…”

A Fast, Reciprocal Pathway between the Lateral Geniculate Nucleus and Visual Cortex in the Macaque Monkey

“…In the primate, magnocellular and parvocellular LGN neurons give rise to axons that terminate most densely in layer 4C of the V1 and less densely in layer 6 (Hubel and Wiesel, 1972;Hendrickson et al, 1978;Blasdel and Lund, 1983). Corticogeniculate feedback arises exclusively from neurons with cell bodies in layer 6 Hendrickson et al, 1978;Fitzpatrick et al, 1994).…”