Anterior forebrain pathway is needed for stable song expression in adult male white-crowned sparrows (Zonotrichia leucophrys)

The anterior forebrain pathway of the avian song system is involved in juvenile song learning, but its function in adult song behavior is not known. This report uses lesions to study the role of a particular forebrain nucleus, IMAN, in the seasonal regeneration of song in adult white-crowned sparrows (Zonotrichia leucophrys oriantha). White-crowned sparrows, even when acoustically isolated as juveniles, crystallize a single song which they maintain throughout adulthood. The lateral portion of the magnocellular nucleus of the anterior neostriatum (1MAN) was lesioned bilaterally in adult males maintained on short days (8 h of light). Daylength was increased to 16 h following the surgeries, and all birds were recorded in the post-lesion singing season. Lesioned birds showed a large decrease in song note frequency following the lesions, significantly larger than did intact, age-matched controls. Further changes were seen in the post-lesion songs of seven of 11 successfully lesioned males. These changes included variability in song pattern, loss of frequency control and addition of new notes, some of which had been practiced during juvenile song development. These changes seemed especially large in birds that had either been acoustically isolated or had not fully copied a tape-tutor song during juvenile song development. These results are the first to indicate that the motor memories for song elements that had been practiced and discarded early in life are retained, and they suggest that 1MAN affects seasonal song expression by selectively reinforcing a particular song pattern.