(A) Diagram of the song system, as in Figure 2A. Recordings were performed in Area X, NBQX/APV were applied in LMAN. (B) PSTH representing the firing rate of a pallidal neuron around DCN stimulation before (black) and during (red) drug application in LMAN. (C) Population data showing no change in response strength before and during LMAN glutamatergic blockade (n = 12 pallidal neurons in 6 birds, paired Wilcoxon test, non-significant). The red curve represents the example shown in B. Inset: confirmation of drugs efficiency by applying drugs around the recorded pallidal neuron (n = 5 pallidal neurons in 5 birds, paired Wilcoxon test, p<0.01). (D) Diagram of the song system. Recordings were performed in Area X, NBQX/APV were applied in MMAN, a nucleus projecting to HVC. (E) PSTH representing the firing rate of pallidal neuron before (black) and during (red) drug application in MMAN. (F) Population data showing the evolution of response strength before and during glutamatergic blockade in MMAN (n = 5 pallidal neurons in 2 birds, paired Wilcoxon test, non-significant). The red curve represents the example shown in E. Inset: confirmation of drug efficiency by applying drug on the recorded pallidal neuron (n = 5 pallidal neurons in 2 birds, paired Wilcoxon test, p<0.05).