Fig. 2

Seasonal changes in singing-driven Arc expression in the song nuclei of canaries. a Singing-driven Arc mRNA expression in first fall, second spring, and second fall groups. (Upper panels) Total singing duration (s) before brain sampling is shown on the panels of each bird. White dots: Arc mRNA expression. Red: cresyl violet counterstain. Scale bar = 1.5 mm. (Lower panels) Higher-magnification images of Arc mRNA expression in HVC, RA, Area X, and LMAN from the same birds represented in the upper panels. Scale bar = 200 μm. b Arc mRNA expression in HVC, RA, Area X, and LMAN in the 30-min singing session. Orange circles: first fall (silent n = 4 and singing n = 4 birds); blue circles: second spring (silent n = 3 and singing n = 6 birds); and orange triangles: second fall (silent n = 3 and singing n = 6 birds). ANCOVA. *p < 0.05, **p < 0.01. c Induction response of Arc mRNA expression in song nuclei after singing in first fall (light orange, n = 4), second spring (blue, n = 6), and second fall (dark orange, n = 6) singers. Two-way ANOVA with Scheffe’s F test. *p < 0.05, **p < 0.01. d Selective expression of singing-driven Arc mRNA in excitatory glutamatergic neurons with Vglut2 in RA (green and red, respectively). DAPl-stained nuclei are shown in blue. Scale bar = 40 μm