Figure 5.

FoxP2 overexpression disrupts behavior-dependent transitions between low and high variability during learning. a, The approach and hypotheses are schematized. On adjacent days, birds were prevented from singing for 2 h or were allowed to sing undirected song for 2 h. The vocal variability immediately following these two epochs was measured. We predicted transitions between variability states in the GFP birds but not FoxP2+ birds. b, Exemplar syllables are shown here with their individual measurements and entropy CV and self-identity measurements based on 20 renditions of the syllable. c, We found divergent effects of FoxP2 overexpression on feature-specific variability, exemplified here by PG, pitch, and entropy CV. In each example, GFP birds showed significantly elevated variability following vocal practice (UD-UD). In FoxP2+ birds, however, the effect of vocal practice depended on the feature being measured: there was no effect on PG CVs, an increase in pitch CV in UD-UD condition, and a decrease in entropy CV in the UD-UD condition. The net result of these changes is a global practice induced increase in variability in GFP birds, which is blocked in FoxP2+ birds. d, A summary diagram of all the feature-specific and global changes observed. Notably, in GFP birds the semicoordinated practice-induced change in variability across multiple features gives rise to a global increase in variability. In contrast, in FoxP2+ birds feature-specific changes are not coordinated and do not give rise to a global change in variability. The means, confidence intervals, and p values represented here are shown in Table 1.