Development of the projections from the dorsal lateral geniculate nucleus to the lateral suprasylvian visual area of cortex in the cat

Autor: Peter D. Spear, Ronald E. Kalil, Lillian Tong
Rok vydání: 1991
Předmět:
Zdroj: The Journal of Comparative Neurology. 314:526-533
ISSN: 1096-9861
0021-9967
DOI: 10.1002/cne.903140309
Popis: In the study reported in the preceding paper, we used retrograde labeling methods to show that the enhanced projection from the thalamus to the posteromedial lateral suprasylvian (PMLS) visual area of cortex that is present in adult cats following neonatal visual cortex damage arises at least partly from surviving neurons in the dorsal lateral geniculate nucleus (LGN). In the C layers of the LGN, many more cells than normal are retrogradely labeled by horseradish peroxidase (HRP) injected into PMLS cortex ipsilateral to a visual cortex lesion. In addition, retrogradely labeled cells are found in the A layers, which normally have no projection to PMLS cortex in adult cats. The purpose of the present study was to investigate the mechanisms of this enhanced projection by examining the normal development of projections from the thalamus, especially the LGN, to PMLS cortex. Injections of HRP were made into PMLS cortex on the day of birth or at 1, 2, 4, or 8 weeks of age. Retrogradely labeled neurons were present in the lateral posterior nucleus, posterior nucleus of Rioch, pulvinar, and medial interlaminar nucleus, as well as in the LGN, at all ages studied. Within the LGN of the youngest kittens, a small number of retrogradely labeled cells was present in the interlaminar zones and among the cells in the A layers that border these zones. Such labeled cells were virtually absent by 8 weeks of age, and they are not found in normal adult cats. Sparse retrograde labeling of C-layer neurons also was present in newborn kittens. The density of labeled C-layer neurons increased 5- to 10-fold between 1 day and 1 week of age and then increased further to adult values by 4 weeks of age. These results indicate that there is not an exuberant projection from the C layers of the LGN to the PMLS cortex in young kittens. This suggests, therefore, that the enhanced projection from the C layers to PMLS cortex after an early visual cortex lesion, described in the preceding paper, is due to new axonal growth. In contrast, at least part of the enhanced projection from the A layers after an early visual cortex lesion may result from the retention of an initially transient projection from the interlaminar zones and immediately adjacent cells in the A layers.
Databáze: OpenAIRE
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