Deafening-induced rapid changes to spine synaptic connectivity in the adult avian vocal basal ganglia.

The basal ganglia have been implicated in auditory-dependent vocal learning and plasticity in human and songbirds, but the underlying neural phenotype remains to be clarified. Here, using confocal imaging and three-dimensional electron microscopy, we investigated striatal structural plasticity in response to hearing loss in Area X, the avian vocal basal ganglia, in adult male zebra finch (Taeniopygia guttata). We observed a rapid elongation of dendritic spines, by approximately 13%, by day 3 after deafening, and a considerable increase in spine synapse density, by approximately 61%, by day 14 after deafening, compared with the controls with an intact cochlea. These findings reveal structural sensitivity of Area X to auditory deprivation and suggest that this striatal plasticity might contribute to deafening-induced changes to learned vocal behavior.