5 - Relationship of LGN Afferents and Cortical Efferents to Cytochrome Oxidase Blobs

Abstract

The demonstration of cytochrome oxidase (CO) blobs in the cat allows investigators to address the organization of processing streams through the visual system of the cat, and whether the CO architecture is as important to cortical organization in this species as it is in primates. This chapter focuses on examining CO blobs in the cat visual cortex, and the way in which they are related to processing streams linking the lateral geniculate nucleus (LGN) inputs and corticocortical outputs. Segregated processing streams exist in the visual cortex of the cat, and these are intimately associated with the CO blobs in areas 17 and 18. Areas 17 and 18 are strongly interconnected, and both make strong projections to area 19, a belt of cortex which borders area 18 laterally. Areas 17 and 18 also project strongly to an area located on the medial bank of the lateral suprasylvian sulcus (LS area), and to area 21a, a small area located on the crown of the suprasylvian gyrus. The patchiness of most or all of these projections results from the projections of adjacent columns of primary visual cortex diverging to innervate separate columns in the target area.