Intrinsic connections in the caudal subdivision of the dorsolateral visual area (DLC) in squirrel monkeys

✍ Scribed by Weller, Rosalyn E.; White, Dreama M.; Walton, Mark M.G.

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 656 KB
• Volume: 420
• Category: Article
• ISSN: 0021-9967
• DOI: 10.1002/(sici)1096-9861(20000424)420:1<52::aid-cne4>3.0.co;2-o

✦ Synopsis

Patterns of intrinsic connections and features of individual intrinsic axons in the caudal subdivision of the dorsolateral visual area (DL C ) were investigated in four squirrel monkeys (Saimiri) following extracellular injections of the tracers biocytin, biotinylated dextran amine, and wheat germ agglutinin conjugated to horseradish peroxidase. Injections were defined in DL C by reference to architectonic borders and patterns of connections with other cortical areas. Intrinsic connections extended up to 6 mm from an injection and were usually anisotropic, extending farther dorsoventrally than anteroposteriorly. Injections that involved the supragranular layers produced up to 20 mainly supragranular patches of projections that had a width of 285 Ϯ 8 m (mean Ϯ standard error) and area of 0.125 Ϯ 0.016 mm 2 . Seventy-four intrinsic axon segments with a total of 3,290 boutons were drawn and their bouton spacing measured. The sample included axons in layers 1, 2-3, 5, and multiple (Ͼ2) layers; horizontally and vertically oriented axons; and axons in an injection halo, patch, or nonpatch region of projections. There were no differences in bouton spacing for axons in halo, patch, or nonpatch regions. Layer 1 axons (n ϭ 7) had a significantly sparser distribution of boutons (median interbouton interval of 45.2 Ϯ 17.8 m) than the layers 2-3 (n ϭ 35) and layer 5 axons (n ϭ 26), which did not differ in bouton spacing (median interbouton intervals of 8.1 Ϯ 0.4 m and 8.4 Ϯ 0.8 m, respectively). Patterns of intrinsic connections in DL C are related to neural organization and properties reported for DL or visual area V4, and are compared to intrinsic connections of other areas.