COMPARISON OF DENDRITIC FIELDS OF LAYER-III PYRAMIDAL NEURONS IN STRIATE AND EXTRASTRIATE VISUAL AREAS OF THE MARMOSET - A LUCIFER YELLOW INTRACELLULAR INJECTION STUDY

Basal dendritic field areas of layer III pyramidal neurons were compar ed between the first (V1), second (V2), dorsolateral (DL) and fundus o f the superior temporal (FST) areas in marmoset monkey visual cortex. These areas correspond to early stages of visual processing (V1, V2) a nd to areas specialized for the analysis of shape (DL) and motion (FST ). Neurons in fixed tangential cortical slices (250 mu m) were injecte d with Lucifer Yellow and immunohistochemically processed for a diamin obenzidine 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 a reas were established based on cytochrome oxidase immunohistochemistry and myelin patterns in the experimental hemisphere, and electrophysio logical recordings in the contralateral hemisphere. Pyramidal neurons in V1 had a mean basal dendritic field area of 1.84 x 10(4) mu m(2) (S EM = 2.04 x 10(3) mu m(2); n = 21). Layer III pyramidal cells in V2 ha d a mean basal dendritic field 1.26 times larger (mean = 2.32 x 10(4) +/- 1.78 x 10(3) mu m(2); n = 42) than that of V1 neurons. The mean de ndritic field area of layer III pyramidal cells in DL in = 76) was 1.5 times larger than that in V1 (mean = 2.75 x 10(4) +/- 1.59 x 10(3) mu m(2)). and that in FST (n = 50) was 2.3 times larger (mean = 4.26 x 1 0(4) +/- 2.79 x 10(3) mu m(2). Our results show that there is a correl ation between tangential dendritic field area of basal dendrites of la yer III pyramidal neurons and modality of visual processing. The incre ase in basal dendritic field area of layer III pyramidal cells may all ow more extensive sampling of inputs as required by higher-order proce ssing of visual information.