Figure 4. The involvement of the forebrain's nucleus RA during the food begging behavior.

(A) Food begging calls induced the expression of immediate early gene c-fos only in RA but not HVC, lMAN, or AreaX. Subsong induced c-fos expression in all four song nuclei. Four telencephalic song system nuclei can be identified by using androgen receptor as a marker. Calibration bar  = 1 mm. (B) Saggital view of the forebrain song system. (C) C-fos expression ratio (song nucleus/surrounding regions) was significantly different in nucleus RA, but not in three other song nuclei, between begging males and non-begging controls (left panel of 4C; Friedman two-way ANOVA; X ² = 25.1; P<0.02); the c-fos expression ratios was higher in all 4 major song nuclei of the birds producing subsong than in birds there were silent (right panel of 4C; Friedman two-way ANOVA; X ² = 37.9; P<0.01). (D) Electrolytic lesion of RA reduced acoustic variability of the food begging calls. The food begging calls of 3 juveniles males before and after electrolytic lesion of nucleus RA. Male 8 is a sham-control male.