Laminar and columnar patterns of geniculocortical projections in the cat: Relationship to cytochrome oxidase

Abstract

We examined the laminar and columnar arrangement of projections from different layers of the lateral geniculate nucleus (LGN) to the visual cortex in the cat. In light of recent reports that cytochrome oxidase blobs (which in primates receive specific geniculate inputs) are also found in the visual cortex of cats, the relationship between cytochrome oxidase staining and geniculate inputs in this species was studied. Injections of wheat germ agglutinin-conjugated horseradish peroxidase were made into the anterior "genu" of the LGN, where isoelevation contours of the geniculate layers are distorted due to the curvature of the nucleus. Consequently, anterograde labeling from the various LGN layers was topographically separated across the surface of the cortex, and labeling in a particular isoelevation representation of the cortex could be associated with a specific layer of the LGN. Labeling from the A layers, which contain X and Y cells, was coextensive with layers 4 and 6 in both area 17 and area 18, as previously reported. Labeling from the C layers, which contain Y and W cells, occupied a zone extending from the 4a/4b border to part way into layer 3 in area 17. The labeling extended throughout layer 4 in area 18. There was also labeling in layer 5a and layer 1 in both area 17 and area 18. Except in layer 1, labeling from the C layers was patchy. In the tangential plane, adjacent sections stained for cytochrome oxidase showed that the patches of labeling from the C laminae aligned with the cytochrome oxidase blobs. The cytochrome blobs were visible in layers 3 and 4a, but not in layer 4b in both areas 17 and 18. These results suggest that W cells project specifically to the layer 3 portion of the blobs, while Y cells, at least those of the C layers, project specifically to the layer 4a portion of the blobs in area 17. The heavy synaptic drive of the Y cells is probably the cause of the elevated metabolism, and thus, higher cytochrome oxidase activity, of the blobs.

Anatomical Demonstration of Ocular Dominance Columns in Striate Cortex of the Squirrel Monkey

“…In the cat, the relationship between the CO staining in the upper layers and the ocular dominance columns is unclear (Dyck and Cynader, 1993;Murphy et al, 1995;Boyd and Matsubara, 1996). In the squirrel monkey, we found no correspondence between the patches and the ocular dominance columns.…”

Comparison of the Laminar Distribution of Input from Areas 17 and 18 of the Visual Cortex to the Lateral Geniculate Nucleus of the Cat

“…Furthermore, the area 18, but not the area 17, feedback pathway sends a stronger projection to layer A1 compared with layer A, whereas layer Cm appears to receive equally strong feedback from both ipsilateral and contralateral eye ocular dominance columns. Both of these characteristics recapitulate the patterns seen in the afferent pathways (Höllander and Vanegas, 1977;LeVay and Ferster, 1977;Geisert, 1980Geisert, , 1985Boyd and Matsubara, 1996). Finally, there is evidence that the Y-cell pathway to area 18 relays more heavily via the lower portion of each A layer (Bowling and Michael, 1984;Geisert, 1985), whereas the X-cell pathway to area 17 shows the opposite distribution.…”

“…It has been suggested that a homologous population of cells might be subsumed within the neighboring ipsilateral eye laminae (Boyd and Matsubara, 1996); indeed, this is one possible explanation for the overrepresentation of layer A1 in the afferent pathway to area 18. Assuming that these cells would receive the same mixture of feedback that is characteristic to layer Cm, this might also explain the apparent anomalies in the pattern of input from area 18.…”

“…Nondominant eye responses can be modified by corticofugal feedback (Schmeilau and Singer, 1977;Varela and Singer, 1987;Murphy and Sillito, 1989) and, because they receive a noneye-specific cortical input, it seems likely that layer Cm cells should be especially susceptible to this influence. Given that layer Cm afferents terminate in ipsilat-erally as well as contralaterally driven ocular dominance columns (Boyd and Matsubara, 1996) and that layer Cm responds differently to abnormal binocular competition during development (Kato et al, 1981;Garraghty et al, 1989;Spear et al, 1989), the possibility that this layer plays a special role in binocular image processing is worth addressing.…”

Close Homolog of L1 and Neuropilin 1 Mediate Guidance of Thalamocortical Axons at the Ventral Telencephalon

“…After 24 h of washing with 0.1 M PBS, the sections were incubated all day at room temperature and overnight at 4°C in fluorescein isothiocyanate (FITC)-or tetramethylrhodamine isothiocyanate (TRITC)-conjugated secondary antibodies. For histology experiments, wild-type (WT) and CHL1 Ϫ littermates were anesthetized and perfused and brains were processed for cytochrome oxidase (Boyd and Matsubara, 1996) or Nissl (Demyanenko et al, 1999).…”