Effects of lesions of the central nucleus of the anterior archistriatum oncontact call and warble song production in the budgerigar (Melopsittacus undulatus)

We studied the effects of both unilateral and bilateral lesions of the cent ral nucleus of the anterior archistriatum (AAc) on the production of contac t calls and warble song in adult male and female budgerigars. Birds were so rted into three experimental groups based on the percentage of AAc destroye d and whether lesions were unilateral or bilateral. The experimental groups were Unilateral Lesion (N = 8), Partial Bilateral Lesion (N = 5), and Bila teral Lesion birds (N = 12). Each group contained both sexes. Unilateral le sions had no demonstrable effects on contact call or warble song production . Bilateral lesions resulted in immediate and permanent disruption of all l earned temporal and spectral characteristics of contact calls, although cal l initiation was not dependent on the AAc. Partial bilateral lesion effects varied with lesion size and location. At least 20-30% sparing of the AAc, including sparing portions of both the dorsal (AAcd) and ventral (AAcv) sub divisions on the same side of the brain, is necessary for production of pre lesion contact call patterns. Warble song was absent in birds with complete bilateral destruction. Two birds with large yet incomplete lesions of the AAc sang after surgery, although the warble song of these birds was extreme ly impoverished and contained only a few of the typical warble song element s. Lesion results indicate that the AAc mediates the production of learned vocal features in male and female budgerigars, with each hemisphere capable of supporting a normal vocal repertoire. (C) 2000 Academic Press.