Influence of Recurrent Excitation and Inhibition on Receptive Field Size and Contrast Sensitivity in Layer 4C of Macaque Striate Cortex

Abstract

Neurons in layer 4C in macaque striate cortex show an increase in receptive fileld size and achromatic contrast sensitivity from the bottom to the top of the layer. Using a computational model which is based on realistic anatomical and physiological data we demonstrate that part of the observed changes can arise from differences in the overall balance between recurrent excitation and lateral inhibition from two different neuron types. The model predicts that - given the above hypotheses - lateral recurrent excitation must come from an increasingly wider range with rise in depth of layer 4C, and lateral inhibition must have higher threshold and gain in upper 4C alpha. The anatomical substrate of recurrent excitation are the stepped projections of spiny stellate cells. As the possible anatomical substrate of differential inhibition we suggest the clutch cell in lower and mid 4C and the alpha-6 (Lund 1987) cell in upper 4C alpha which replaces the clutch cell as a somatic inhibitor.