The patchy pattern of retrograde labeling produced
by injections of anatomical tracers into the lateral suprasylvian
(LS) visual area was compared to the cytochrome oxidase
(CO) blobs in cat visual cortex. Following large injections
of anatomical tracers in LS, retrograde labeling formed
an irregular lattice of patches with a spacing of slightly
less than 1 mm in area 17, and slightly greater than 1
mm in area 18. By comparing labeling in alternate serial
sections, patches of LS-projecting cells in both areas
were found to align with CO blobs. The conclusion of alignment
between CO blob columns and patches of LS-projecting cells
was confirmed by a quantitative analysis which showed a
significant correlation between the local density of LS-projecting
cells in reconstructions of charted cells and the intensity
of CO staining in the CO-reacted sections. As for areas
17 and 18, labeling in other afferent areas of LS was also
patchy with a spacing on the order of 1 mm except for area
19 where we found patches of LS-projecting cells with a
larger spacing, roughly 2 mm. No matching fluctuations
in CO density could be discerned in area 19, however. In
conjunction with recent evidence that CO blob columns in
cats receive strong input from Y-cells of the lateral geniculate
nucleus (Boyd & Matsubara, 1996; Shoham, et al., 1996),
these data support the hypothesis (Shipp & Grant, 1991)
that the patches of LS-projecting cells correspond to Y-cell
input columns. As a relationship between the CO architecture
and certain classes of efferent cells has previously been
shown in primates, these findings show new similarities
between CO blobs in different mammalian species.
Rewiring of Transcortical Projections to Middle Suprasylvian Cortex Following Early Removal of Cat Areas 17 and 18