Overall patterns of eye-specific retino-geniculo-cortical projections to layers III, IV, and VI in primary visual cortex of the greater galago (Otolemur crassicudatus), and correlation with cytochrome oxidase blobs.
Jaime F Olavarria, Huixin Qi, Toru Takahata, Jon H Kaas
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引用次数: 0
Abstract
Studies in the greater galago have not provided a comprehensive description of the organization of eye-specific retino-geniculate-cortical projections to the recipient layers in V1. Here we demonstrate the overall patterns of ocular dominance domains in layers III, IV, and VI revealed following a monocular injection of the transneuronal tracer wheat germ agglutinin conjugated with horseradish peroxidase (WGA-HRP). We also correlate these patterns with the array of cytochrome oxidase (CO) blobs in tangential sections through the unfolded and flattened cortex. In layer IV, we observed for the first time that eye-specific domains form an interconnected pattern of bands 200-250 μm wide arranged such that they do not show orientation bias and do not meet the V1 border at right angles, as is the case in macaques. We also observed distinct WGA-HRP labeled patches in layers III and VI. The patches in layer III, likely corresponding to patches of K lateral geniculate nucleus (LGN) input, align with layer IV ocular dominance columns (ODCs) of the same eye dominance and overlap partially with virtually all CO blobs in both hemispheres, implying that CO blobs receive K LGN input from both eyes. We further found that CO blobs straddle the border between layer IV ODCs, such that the distribution of CO staining is approximately equal over ipsilateral and contralateral ODCs. These results, together with studies showing that a high percentage of cells in CO blobs are monocular, suggest that CO blobs consist of ipsilateral and contralateral subregions that are in register with underlying layer IV ODCs of the same eye dominance. In macaques and humans, CO blobs are centered on ODCs in layer IV. Our finding that CO blobs in galago straddle the border of neighboring layer IV ODCs suggests that this novel feature may represent an alternative way by which visual information is processed by eye-specific modular architecture in mammalian V1.
期刊介绍:
Visual Neuroscience is an international journal devoted to the publication of experimental and theoretical research on biological mechanisms of vision. A major goal of publication is to bring together in one journal a broad range of studies that reflect the diversity and originality of all aspects of neuroscience research relating to the visual system. Contributions may address molecular, cellular or systems-level processes in either vertebrate or invertebrate species. The journal publishes work based on a wide range of technical approaches, including molecular genetics, anatomy, physiology, psychophysics and imaging, and utilizing comparative, developmental, theoretical or computational approaches to understand the biology of vision and visuo-motor control. The journal also publishes research seeking to understand disorders of the visual system and strategies for restoring vision. Studies based exclusively on clinical, psychophysiological or behavioral data are welcomed, provided that they address questions concerning neural mechanisms of vision or provide insight into visual dysfunction.