Fig. 2.

Blocking inhibition reveals an excitatory bias for learned songs in dorsal NCM. A: song spectrograms and response PSTHs for learned songs (left) and unfamiliar songs (right) for an example site in dorsal NCM. Solid red denotes PSTH with inhibition blocked. Black line denotes PSTH with inhibition intact. B: histograms of average firing-rate (FR) differences between learned and unfamiliar songs for all dorsal sites with inhibition intact (top) and inhibition blocked (bottom right). Scatter plot (bottom left) shows that inhibition increases the firing-rate difference between learned and unfamiliar songs for nearly all sites. C: mean (±SE) song firing rates in dorsal NCM normalized by the SD of firing rates to all songs (z-scores). The average effect of blocking inhibition has been subtracted from these numbers. Significant differences between learned and unfamiliar songs are only observed when inhibition is blocked. sp/s, spikes/s. Paired t-tests: *P < 0.05; **P < 0.01.