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Updated: Aug 14, 2026

The Gateway to the Brain: Dissecting the Primate Eye
Published on: May 27, 2009
[Morphological differentiation in connection with the functional specialization of the mammalian visual system
Abstract:
In the mammals there are two visual pathways: 1. retino-geniculo-cortical (as a rule area 17) and 2. retino-colliculo-thalamo-(pulvino-) cortical (mainly areas 18 and 19). In connection with the visual specialization the first pathway only shows on the subcortical level (dorsal lateral geniculate nucleus) and on the cortical level (area 17) morphological differentiations. In contrast, the differentiation of parts of the second pathway (pulvinar complex and associative cortex) is the expression of a higher evolution of this system. In the dLGN the input-zones of the ipsi- and contralateral eye are separated more and more. This becomes visible by a cytoarchitectonic lamination of the dLGN. In area 17 layer IV is--in connection with the specialization--increasingly divided in sublayers where the fibers of the X- and Y-system terminate separately.
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