Basal ganglia function, stuttering, sequencing, and repair in adult songbirds.

A pallial-basal-ganglia-thalamic-pallial loop in songbirds is involved in vocal motor learning. Damage to its basal ganglia part, Area X, in adult zebra finches has been noted to have no strong effects on song and its function is unclear. Here we report that neurotoxic damage to adult Area X induced changes in singing tempo and global syllable sequencing in all animals, and considerably increased syllable repetition in birds whose song motifs ended with minor repetitions before lesioning. This stuttering-like behavior started at one month, and improved over six months. Unexpectedly, the lesioned region showed considerable recovery, including immigration of newly generated or repaired neurons that became active during singing. The timing of the recovery and stuttering suggest that immature recovering activity of the circuit might be associated with stuttering. These findings indicate that even after juvenile learning is complete, the adult striatum plays a role in higher level organization of learned vocalizations.

Song-related dopamine receptor regulation in Area X of zebra finch male.

Song learning and production have many parallels with speech and the mechanisms of their control have been studied extensively. There is an increasing amount of evidence that the dopaminergic system is involved in song learning and maintenance. Dopamine receptors show distinct expression in most of the song nuclei and the highest levels in Area X of the striatum. Here we have investigated whether the mRNA expressions for D1A, D1B, and D2 receptors in Area X are associated with quantitative and/or qualitative characteristics of zebra finch song. We found that quantitative parameters of song such as the amount of songs sang, motif duration, and numbers of distinct syllables and/or notes per motif did not correlate with expression of D1A, D1B nor D2 receptors in Area X or surrounding striatum. However, the mean accuracy of the song correlated negatively with D1A receptor expression levels and the sequential match correlated positively with D2 receptor expression levels in Area X relative to the surrounding striatum. These data suggest that dopamine receptor densities in Area X are associated with song variability.