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 no t known. This report uses lesions to study the role of a particular fo rebrain nucleus, IMAN, in the seasonal regeneration of song in adult w hite-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 por tion of the magnocellular nucleus of the anterior neostriatum (lMAN) w as lesioned bilaterally in adult males maintained on short days (8 h o f light). Daylength was increased to 16 h following the surgeries, and all birds were recorded in the post-lesion singing season. Lesioned b irds showed a large decrease in song note frequency following the lesi ons, significantly larger than did intact, age-matched controls. Furth er changes were seen in the post-lesion songs of seven of 11 successfu lly lesioned males. These changes included variability in song pattern , loss of frequency control and addition of new notes, some of which h ad been practiced during juvenile song development. These changes seem ed especially large in birds that had either been acoustically isolate d or had not fully copied a tape-tutor song during juvenile song devel opment. These results are the first to indicate that the motor memorie s for song elements that had been practiced and discarded early in lif e are retained, and they suggest that IMAN affects seasonal song expre ssion by selectively reinforcing a particular song pattern. (C) 1998 E lsevier Science B.V. All rights reserved.