Interruption of a basal ganglia-forebrain circuit prevents plasticity of learned vocalizations

Birdsong, like speech, is a learned vocal behaviour that relies greatly on hearing; in both songbirds(1) and humans(2) the removal of auditory feedbac k by deafening leads to a gradual deterioration of adult vocal production. Here we investigate the neural mechanisms that contribute to the processing of auditory feedback during the maintenance of song in adult zebra finches . We show that the deleterious effects on song production that normally fol low deafening can be prevented by a second insult to the nervous system-the lesion of a basal ganglia-forebrain circuit. The results suggest that the removal of auditory feedback leads to the generation of an instructive sign al that actively drives nonadaptive changes in song; they also suggest that this instructive signal is generated within (or conveyed through) the basa l ganglia-forebrain pathway. Our findings provide evidence that cortical-ba sal ganglia circuits may participate in the evaluation of sensory feedback during calibration of motor performance, and demonstrate that damage to suc h circuits can have little effect on previously learned behaviour while con spicuously disrupting the capacity to adaptively modify that behaviour.