THE DISTRIBUTION OF CORTICOTECTAL PROJECTION NEURONS CORRELATES WITH THE INTERBLOB COMPARTMENT IN MACAQUE STRIATE CORTEX

While much attention has been given to the correlation between cytochr ome-oxidase (GO) compartments and patterns of cortico-cortical project ions originating from supragranular layers in the striate cortex, litt le is known in this regard about patterns of cortico-subcortical proje ctions originating from infragranular cortex. We studied the tangentia l distribution of the striate cortex neurons projecting to the superio r colliculus and used two approaches to analyze the relationship of th is distribution to the arrangement of CO ''blobs.'' First, chi-square analysis indicated that significantly fewer labeled neurons were found within the CO blob compartment than the number expected for a random distribution. Second, spatial cross-correlation analysis -which circum vents the inherent subjectivity of delineating blob boundaries reveale d an area around blob centers in which there was a decreased probabili ty of encountering labeled cells. The size of this area compared well with that of our outlines of CO blobs. We conclude that corticotectal projection neurons in the striate cortex are distributed preferentiall y within the interblob compartment of the infragranular striate cortex . These results demonstrate that the spatial distribution of cortico-s ubcortical projection neurons within infragranular cortex can correlat e with the CO architecture of the primary visual cortex.