Abstract

To help understand the role of long-range, clustered lateral connections in the superficial layers of macaque striate cortex (area V1), we have examined the relationship of the patterns of intrinsic connections to cytochrome oxidase (CO) blobs, interblobs, and ocular dominance (OD) bands, using biocytin based neuroanatomical tracing, CO histochemistry, and optical imaging. Microinjections of biocytin in layer 3 resulted in an asymmetric field (average anisotropy of 1.8; maximum spread—3.7 mm) of labeled axon terminal clusters in layers 1–3, with the longer axis of the label spread oriented orthogonal to the rows of blobs and imaged OD stripes, parallel to the V1/V2 border. These labeled terminal patches (n = 186) from either blob or interblob injections (n = 20) revealed a 71% (132 out of 186) commitment of patches to the same compartment as the injection site; 11% (20 out of 186) to the opposite compartment, and 18% (34 out of 186) to borders of blob-interblob compartments, indicating that the connectivity pattern is not strictly blob to blob, or interblob to interblob (p < 0.005; $$$2) In injections placed within single OD domains (n = 11), 54% of the resulting labeled terminal patches (43 out of 79) fell into the same OD territories as the injection sites, 28% (22 out of 79) into the opposite OD regions, and 18% (14 out of 79) on borders, showing some connectional bias toward same-eye compartments (p < 0.02; ANOVA). Individual injection cases, however, varied in the degree (50–100% for CO patterns, 22–100% for 0D patterns) to which they showed same-compartment connectivity. These results reveal that while connectivity between similar compartments predominates (e.g., blob to blob, right eye column to right eye column), interactions do occur between functionally different regions.