Fig. 1
Seasonal song plasticity in the canary. a Diagram of the song circuits. The posterior vocal pathway and the anterior forebrain pathway (pallial–basal ganglia–thalamic circuit) are represented as solid and dotted white lines, respectively. HVC (proper name); RA, robust nucleus of the arcopallium; Area X, Area X of the striatum; DLM, dorsal lateral nucleus of the medial thalamus; LMAN, lateral magnocellular nucleus of the anterior nidopallium; nXIIts, tracheosyringeal portion of the hypoglossal nucleus. d/v/a/p, dorsal/ventral/anterior/posterior. b (Top) Timeline of song sensorimotor learning period of the zebra finch, a closed-ended vocal learner. phd, post-hatching day. (Middle) Early plastic and crystallized songs of a zebra finch. (Bottom) Typical singing-driven expressions of Arc mRNA (white) in the song nuclei, HVC, RA, LMAN, and Area X of zebra finch juveniles (silent, 52 phd; singing, 47 phd) and adults (silent, 124 phd; singing, 112 phd). Total singing duration(s) before brain sampling is shown in the panel. White dots: Arc mRNA expression. Red: cresyl violet counterstain. Scale bar = 1.5 mm. Arc expressions in RA were enlarged with a white outline. All images are adapted from Hayase et al. 2018 PLoS Biology [41]. c (Top) Timeline of the song sensorimotor learning period of the canary, an open-ended vocal learner. (Bottom) Seasonal changes in song plasticity of canary songs. Colored lines: crystallized repetitive phrases of the structured song in second spring. d Mean similarity scores between adjacent syllables in first fall (n = 4 birds), second spring (n = 6 birds), and second fall (n = 6 birds) (300 syllable sets/bird). e CV of similarity scores between adjacent syllables in first fall, second spring, and second fall. For (D) and (E), one-way ANOVA with Scheffe’s F test. *p < 0.05, **p < 0.01. f The mean cumulative singing duration (sec) in 30-min singing sessions before brain sampling from singers in first fall (n = 4 birds), second spring (n = 6 birds), and second fall (n = 6 birds). One-way ANOVA. n.s.p > 0.05