Figure 2.

Verifications for the PIR hypothesis. A, Identified putative connections between all single units from one experiment. Color code: blue, no connection; red, inhibition; green, excitation; and orange, PIR. Some target neurons that display rebound upon inhibition from some interneurons (e.g., interneurons number 18 and 30 onto neuron 17) also receive excitatory connections from some principal cells (e.g., principal cells 8, 12, 15, and 21 onto neuron 17). B, Comparison between average values of the rebound strength and the extent of overlap between two sets of spikes of the target cell: those contributing to the statistically significant peaks in the PIR CCGs and those contributing to the statistically significant peaks in the CCGs for normal excitations. The low strength of overlap suggests that identified excitatory connections cannot account for the rebound excitation observed in the CCG of PIR pairs. The bar diagram considers all PIR pairs in which the target cell is also the target in at least one excitatory connection.