RESUMO
Visual receptive fields (RFs) were mapped inside and outside the cortical representation of the optic disk in the striate cortex (area V1) of anesthetized and paralyzed Cebus monkeys. Unexpectedly, most cells were found to be binocularly driven, and the RFs mapped with contralateral-eye stimulation progressed in a topographically appropriate fashion as the optic disk sector was crossed. Activation of these neurons by the contralateral eye was shown to depend on stimulation of the parts of the retina around the optic disk. Outside the optic disk representation, a similar effect was demonstrated by obstructing the "classical" RF with masks 5-10 times larger in size. In all cases, visual stimuli presented around the mask could be used to accurately interpolate the position of the hidden RF. These properties reflect, at a cellular level, the process of "filling in" that allows for completion of the visual image across natural and artificially induced scotomas.
Assuntos
Córtex Visual/fisiologia , Percepção Visual , Animais , Mapeamento Encefálico , Cebus , Retina/fisiologia , Córtex Visual/anatomia & histologia , Campos VisuaisRESUMO
1. The topographic organization of the cortical visual areas in the Cebus monkey and their anatomical connections support the subdivision of the visual pathways into ventral and dorsal streams of visual information processing. 2. We propose that the dorsal stream, as defined by Ungerleider and Mishkin (In: Ingle DJ, Goodale MA and Mansfield RJW (Editors), Analysis of Visual Behavior. MIT Press, Boston, 1982), be subdivided into dorsolateral and dorsomedial streams, which are concerned with different aspects of the processing of motion and spatial perception. 3. The data support the hypothesis of concurrent, modular processing of visual attributes in cortical visual areas in the different streams, and highlight some features of the visual field representation in each area which may reflect functional specialization of these streams. 4. The visual topography is locally disrupted in some cortical areas by the existence of functionally different modules. However, a global visuotopic organization is preserved in most areas. 5. The visuotopic organization may provide the address of space coordinates to integrate information concerning the same retinotopic locus across different visual areas.
Assuntos
Córtex Visual/anatomia & histologia , Campos Visuais , Vias Visuais/anatomia & histologia , Animais , Cebus/anatomia & histologia , Complexo IV da Cadeia de Transporte de Elétrons/metabolismo , Histocitoquímica , Córtex Visual/enzimologia , Percepção VisualRESUMO
1. The topographic organization of the cortical visual areas in the Cebus monkey and their anatomical connections support the subdivision of the visuaol pathways into ventral and dorsal streams of visual information provessing. 2. We propose that the dorsal stream, as defined by Ungerleider and Mishkin (In: Ingle DJ, Goodale MA and Mansfield RJW (Editors), Analysis of Visual Behavior, MIT Press, Boston, 1982), be subdivided into dorsolateral and dorsomedial streams, which are concerned with different aspects of the processing of motion and spatial perception. 3. The data support the hypothesis of concurrent, modular processing of visual attributes in cortical visual areas in the different streams, and highlight some features of the visual field representation in each area which may reflect functional specialization of these streams. 4. The visual topography is locally disrupted in some cortical areas by the existence of functionally different modules, However, a global visuotopic organization is preserved in most areas. 5. The visuotopic organization may provide the address of space coordinates to integrate information concerning the same retinotopic across different visual areas
Assuntos
Animais , Córtex Visual/anatomia & histologia , Campos Visuais , Vias Visuais/anatomia & histologia , Cebus/anatomia & histologia , Complexo IV da Cadeia de Transporte de Elétrons/metabolismo , Histocitoquímica , Córtex Visual/enzimologiaRESUMO
The presence of ocular dominance (OD) stripes in layer IVc of striate cortex (V1) is characteristic of all Old World simians so far studied. In contrast, some species of New World monkeys do not have ocular dominance stripes, and in those that do, the pattern of stripes may be different from that shown in Old World monkeys. This difference has led to the suggestion that OD stripes evolved independently in both groups. We have mapped the entire system of OD stripes in the New World monkey Cebus, by means of cytochrome oxidase histochemistry after monocular enucleation. A striking similarity was found between the patterns in Cebus and Macaca, which is suggestive of common ancestry, rather than parallel evolution.