Comparison of dendritic fields of layer III pyramidal neurons in striate and extrastriate visual areas of the marmoset: a Lucifer yellow intracellular injection.

Basal dendritic field areas of layer III pyramidal neurons were compared between the first (V1), second (V2), dorsolateral (DL) and fundus of the superior temporal (FST) areas in marmoset monkey visual cortex. These areas correspond to early stages of visual processing (V1, V2) and to areas specialized for the analysis of shape (DL) and motion (FST). Neurons in fixed tangential cortical slices (250 microns) were injected with Lucifer Yellow and immunohistochemically processed for a diaminobenzidine reaction product. Dendritic field areas were calculated for layer III pyramidal cells whose complete basal projection was judged to be within the section (n = 189). Borders between different visual areas were established based on cytochrome oxidase immunohistochemistry and myelin patterns in the experimental hemisphere, and electrophysiological recordings in the contralateral hemisphere. Pyramidal neurons in V1 had a mean basal dendritic field area of 1.84 x 10(4) microns2 (SEM = 2.04 x 10(3) microns2; n = 21). Layer III pyramidal cells in V2 had a mean basal dendritic field 1.26 times larger (mean = 2.32 x 10(4) +/- 1.78 x 10(3) microns2; n = 42) than that of V1 neurons. The mean dendritic field area of layer III pyramidal cells in DL (n = 76) was 1.5 times larger than that in V1 (mean = 2.75 x 10(4) +/- 1.59 x 10(3) microns2), and that in FST (n = 50) was 2.3 times larger (mean = 4.26 x 10(4) +/- 2.79 x 10(3) microns2). Our results show that there is a correlation between tangential dendritic field area of basal dendrites of layer III pyramidal neurons and modality of visual processing. The increase in basal dendritic field area of layer III pyramidal cells may allow more extensive sampling of inputs as required by higher-order processing of visual information.