FoxP2 regulation during undirected singing in adult songbirds

Abstract

Learned vocal communication, including human speech, is a socially influenced behavior limited to certain animals. This ability requires auditory feedback during vocalization, which allows for on-line evaluation, to achieve the desired vocal output. To date, FOXP2 (forkhead box P2), a transcriptional repressor, is the only molecule directly linked to human speech. Identified FOXP2 mutations cause orofacial dyspraxia accompanied by abnormalities in corticostriatal circuitry controlling voluntary orofacial movements. These observations implicate FOXP2 in the developmental formation of neural circuits used in speech, but whether FOXP2 additionally plays an active role in mature circuitry was unknown. To address this question, we use a songbird, the zebra finch (Taeniopygia guttata), whose learned song and underlying circuitry are well characterized. We show that, when adult males sing, FoxP2 mRNA is acutely downregulated within area X, the specific region of the songbird striatum dedicated to song. Furthermore, we find downregulation in males that sing by themselves (undirected singers) but not in males that sing to females (directed singers). This FoxP2 downregulation cannot be a simple consequence of the motor act because birds sang in both directed and undirected contexts. Our data suggest that FoxP2 is important not only for the formation but also for the function of vocal control circuitry. Social context-dependent, acute changes in FoxP2 within the basal ganglia of adult songbirds also suggest, by analogy, that the core deficits of affected humans extend beyond development and beyond basic central motor control.

Figure 1.

Area X FoxP2 levels vary between mixed singers. a, FoxP2 levels in area X are similar to those of surrounding StM in nonsingers but appear downregulated in many mixed singers. The variability between mixed singers exceeds that between nonsingers (p < 0.05). b, Top, Average pixel density obtained from line scans through representative images of hemicoronal brain sections (bottom) depict FoxP2 levels measured at the widest mediolateral extent. FoxP2 levels in area X of the mixed singer that sang the fewest motifs (88 motifs; right) appear lower than those in the nonsinger (left). c, High ZENK expression in area X of mixed singers (right; same bird as in b, right) indicates that, although housed with females, males sang some undirected songs. Left image from a 100% directed singer is shown for comparison. Schematic above indicates neuroanatomical landmarks. Arrowheads indicate area X. P, Pallium; S, striatum; X, area X.

Figure 2.

FoxP2 levels are low in area X of undirected singers. Representative photomicrographs show lower levels of FoxP2 in area X of an undirected singer detected by both mid-probe and 3`-probes compared with those in a nonsinger or a directed singer.

Figure 3.

Undirected singing acutely downregulates FoxP2 in area X. Bar graphs show group and individual values of FoxP2 expression in area X relative to surrounding StM (mean ± SEM). Levels in undirected singers (white) are lower than in nonsingers (gray) or directed singers (black) (mid-probe, p = 0.0006; 3`-probe, p = 0.0005). Nonsinging data are the same as shown in Figure 1.

Figure 4.

Trends in the correlation between FoxP2 and singing differ between directed (black; p = 0.26) and undirected (white; p = 0.18) singers.