Document Detail

Visuotopic organization of corticocortical connections in the visual system of the cat.
MedLine Citation:
PMID:  1629397     Owner:  NLM     Status:  MEDLINE    
It has recently been demonstrated that, in contrast with the retinogeniculocortical projection, the corticocortical connections in the cat present a high degree of convergence and divergence. This suggests that some corticocortical connections link nonvisuotopically corresponding regions. Using fine-grain electrophysiological mapping and anatomical tracing, we have set out to test this possibility by placing a small injection of retrograde tracer in area 17 and by comparing the extent of visual field encoded in the region of area 18 containing labeled cells and that represented in the uptake zone. The results demonstrate that the size of the labeled region on the surface of area 18 is independent of eccentricity and that, despite its anisotrophy, this region of labeling encodes a broadly circular region of visual field that is larger than that encoded in the uptake zone of the tracer in area 17. For example, in the representation of lower visual field, a virtual point in area 17 that encodes a visual field region 4 degrees in diameter receives afferents from a region of area 18 encoding a region 11 degrees wide. Examination of the density of labeled cells in the labeled zone in area 18 reveals that the highest density is observed in a region in visuotopic correspondence with the injection site. However, high labeling density is also occasionally found in patches that do not represent the same visual field region as the injection site. Many receptive fields of neurons recorded in the labeled zone in area 18 only partially overlap or fail to overlap the visual field region encoded by the injection site. The results also demonstrate that the extent of visual field encoded in the labeled zone in area 18 is the same as that represented in the region of intrinsic labeling in area 17. It is suggested that cortical afferents coming from several cortical areas and converging on a column of cells in area 17 cover the same extent of visual field and that this cortical network constitutes the structural basis for the modulatory regions of the receptive field as well as the synchronization of neurons in different cortical areas.
P A Salin; P Girard; H Kennedy; J Bullier
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The Journal of comparative neurology     Volume:  320     ISSN:  0021-9967     ISO Abbreviation:  J. Comp. Neurol.     Publication Date:  1992 Jun 
Date Detail:
Created Date:  1992-08-18     Completed Date:  1992-08-18     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0406041     Medline TA:  J Comp Neurol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  415-34     Citation Subset:  IM    
INSERM 94, Bron, France.
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MeSH Terms
Brain Mapping
Cats / physiology*
Cell Count
Neurons / cytology
Visual Cortex / cytology,  physiology*
Visual Fields
Visual Pathways / physiology*

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