Figure 4

Excitation and inhibition within single subregions of the receptive field. (a) Histogram of absolute values of the push-pull index (bin size = 0.1) with a graphical explanation of the index below. Filled bars, cells with segregated On and Off subregions (overlap index ≤0.09); open bars, cells with overlapping On and Off subfields (overlap index >0.3) or with just one subregion; NR indicates that there was no response to the flash stimulus. The asterisk marks a pyramid in layer 2+3 whose dendrites extended into layer 4 and whose receptive field had push-pull in only one of two subregions. The distribution of values was not unimodal, probability of rejection 0.99 (Hartigan's dip test). (b) Comparison of values of push-pull index for thalamic receptive fields (gray) and simple cortical receptive fields with segregated On and Off subregions (black); bin size = 0.1. (c) Overlap index values of excitatory and inhibitory responses to stimuli of the opposite contrast in thalamic receptive field centers (gray) and in the individual subfields of cortical cells with separated subregions (black); bin size = 0.1.