Figure 10. Infusion of the D1 receptor antagonist SCH23390 in Area X abolishes differences in song variability due to social context. A, Example of a song spectrogram of bird 1. This bird displayed five subsyllabic elements with a clear harmonic structure. The dashed ellipse indicates the subsyllabic element considered in C. B, cresyl violet staining of a 50 μm parasagittal brain section showing the track of the cannula used to infuse drugs in the behaving bird. Solid gray lines denote the position of the cannula. Area X contours are outlined with white arrows, while LMAN is outlined with black arrows. The dashed white line outlines the pallial–subpallial lamina, which separates the BG from pallial structures. C, Distribution of the frequency of the lowest harmonic of the subsyllabic element highlighted in A in four different conditions: in the absence of female before surgery (dotted dashed black line), in the presence of a female before surgery (solid black line), in the presence of a female during SCH23390 infusion in Area X (solid red line), and in the presence of a female during saline infusion in Area X (blue line, following the SCH23390 infusion). D, Context-dependent changes in song variability in three different conditions. In each paired graph, the left column refers to singing in the absence of female, while the right column refers to singing in the presence of a female. Left, Before surgery; middle, during the infusion of SCH23390; right, during saline infusion. Saline infusion followed SCH infusion in three of four birds. The two social contexts are associated with different song variability before surgery and during saline infusion, while SCH infusion abolishes differences in variability related to social context. E, Relative song variability in the three behavioral conditions for the 12 subsyllabic elements displayed context-related changes in variability. The relative song variability is calculated as the SD of the lower harmonic frequency when the bird was singing to a female in each condition divided by the SD of the lowest harmonic frequency when singing alone before surgery. Left, Before surgery; middle, during the infusion of SCH23390; right, during saline infusion. In D and E, the red discs indicate values corresponding to the subsyllabic element shown in A and C.