Cortical Connections of Visual Area V4 in the Macaque
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V4 is a visual area in the macaque cortex located on the prelunate gyrus and extending onto the anterior bank of the lunate sulcus and the posterior bank of the superior temporal sulcus. Previous investigations in area V4 have shown that neurons in this visual area send projections into the inferior temporal cortex, which has been shown to mediate the recognition of objects. It has been hypothesized that area V4 is part of a hierarchical pathway which begins in the primary visual cortex, V1, and continues through other visual areas, V2 and V3, both of which send projections to V4. Moving progressively through the pathway, it has been shown that the complexity of the visual stimulus needed to drive these neurons also increases. These facts are presumably due to the convergence of input from earlier visual areas to subsequent projection fields. While the cortical connections of visual areas such as striate cortex, V2 and V3 have been extensively studied, those of V4 have not. It was the intention of this study to further elucidate the anatomical connections of visual cortex, especially those of area V4. These results showed that area V4 receives input from V2 and V3 and provides afferents to parts of the inferior temporal cortex. Whereas foveal or central representations of V4 appeared to project to both anatomical areas TEO and TE in the inferior temporal cortex, more peripheral representations of V4 projected only to TE. Additional cortical connections of V4 were found in the depths of the intraparietal and the superior temporal sulci and in the frontal eye fields. The most intriguing result was the heavier and more extensive input to inferior temporal cortex from the foveal sites in V4 relative to the peripheral sites and the heavier and more extensive input to the posterior parietal cortex from the peripheral sites in V4 relative to the fovial sites. These results suggest that inputs for foveal, or central, vision may be sent preferentially to the inferior temporal cortex while inputs for peripheral vision may be sent preferentially to the posterior parietal cortex. This finding is consistent with the object recognition and visuospatial function of these two respective cortices.