Relationships between cytochrome oxidase (CO) blobs in primate primary visual cortex (V1) and the distribution of neurons projecting to the middle temporal area (MT)

Abstract

The cytochrome oxidase (CO) blobs and interblobs in layer 3B of primate visual cortex have different sets of corticocortical connections. Cortical layers below layer 3B also project corticocortically, but the relationship of efferent projections from the deeper layers to the overlying blob/interblob architecture is less clear. We studied the tangential organization of neurons projecting from primary visual cortex (V1) to the middle temporal visual area (MT) and their relationship to the CO blobs. MT‐projecting neurons in two primate species, bush babies and owl monkeys, were retrogradely labeled, then charted in tangential sections, and compared to the positions of the overlying CO blobs. In both primate species, MT‐projecting neurons in layer 3C were unevenly distributed in the tangential plane, with dense patches of labeled cells that were aligned with the CO blobs. A novel two‐dimensional spatial correlation method was used to show the colocalization of MT‐projecting cells with the overlying blobs. Chi‐square analyses performed with the cortical surface equally divided into compartments of blob, interblob, and blob/interblob borders showed that blob columns tended to have about 1.5 times more MT‐projecting cells (P < 0.0001) than interblob columns. Similar analyses were applied to published data on V1 cells projecting to area MT in macaque monkey (Shipp and Zeki [1989] Euro J Neurosci 1:310–332). Again, the results showed a significant correlation between the cell distribution and CO blobs. Taken together, these results suggest that layer 3C is not uniform but is made up of a mosaic of cells that project to area MT and cells that project to some other location. These findings also indicate that the mosaic organization of layer 3C is related in some unique way to the overlying CO architecture. J. Comp. Neurol. 409:573–591, 1999. © 1999 Wiley‐Liss, Inc.

Local Circuits of V1 Layer 4B Neurons Projecting to V2 Thick Stripes Define Distinct Cell Classes and Avoid Cytochrome Oxidase Blobs

“…Hierarchical cluster analysis (Cauli et al, 2000;Briggs et al, 2016) was performed to classify neurons based on the percentage of total axon length in L2/3, L4A, L4B, L4C, L5, and L6. Although L4A and L4C generally contained axonal branches passing through to other layers, and L6 was generally not a primary target, all layers were used for this analysis to avoid any subjective biasing of the data.…”

“…The hierarchical cluster analysis plots the position of each cell in an N-dimensional space based on the number of metrics used to describe the cell, which in this study was axon length across six different layers. The distance between cells in this space was calculated using squared Euclidian distance, and linkages between cells were created using the Wards method (Briggs et al, 2016). Statistical comparisons of axon lengths in different layers, for different cell classes identified by the cluster analysis, were performed using a Kruskal-Wallis test corrected for multiple comparisons using Bonferroni's correction, Figure 1.…”

“…Briefly, digitized images of CO-stained tissue were processed using low-pass, equalization, and exponential filters (Image-Pro Plus, Media Cybernetics). The blobs were outlined by segmenting out the darkest 33% of pixels in the gray scale CO image (Boyd and Casagrande, 1999;Sincich and Horton, 2005a). Blob centers were defined as the darkest spot within each blob and the lightest pixels represented interblob centers.…”

“…In this study, to understand how local V1 circuits of L4B cells relate to their target V2 stripe type, we have used a green fluorescent protein (GFP)-expressing G-deleted rabies virus (GdRV; Nassi and Wickersham et al, 2007;Briggs et al, 2016) to obtain Golgilike fills of L4B neurons that specifically project to the thick CO stripes of V2, and have fully reconstructed these cells' dendritic and axonal processes. We find morphological evidence for at least two distinct classes of neurons, including a novel neuron type not previously described.…”

Complete Pattern of Ocular Dominance Columns in Human Primary Visual Cortex

“…Consequently, the center alone is less useful for defining the location of a patch than an algorithm that incorporates information about the entire structure. For this reason, we performed a spatial correlation to quantify the relationship between patches and ocular dominance columns (Lia and Olavarria, 1996;Boyd and Casagrande, 1999;Adams and Horton, 2006b). To define patches, a single CO section was high-pass Fourier filtered to correct for global changes in section density (attributable to small differences in layer 3 depth).…”