Song selectivity in the pallial-basal ganglia song circuit of zebra finches raised without tutor song exposure

Acoustic experience critically influences auditory cortical development as well as emergence of highly selective auditory neurons in the songbird sensorimotor circuit. In adult zebra finches, these song-selective neurons respond better to the bird's own song (BOS) than to songs of other conspecifics. Birds learn their songs by memorizing a tutor's song and then matching auditory feedback of their voice to the tutor song memory. Song-selective neurons in the pallial-basal ganglia circuit called the anterior forebrain pathway (AFP) reflect the development of BOS. However, during learning, they also respond strongly to tutor song and are compromised in their adult selectivity when birds are prevented from matching BOS to tutor, suggesting that selectivity depends on tutor song learning as well as sensorimotor matching of BOS feedback to the tutor song memory. We examined the contribution of sensory learning of tutor song to song selectivity by recording from AFP neurons in birds reared without exposure to adult conspecifics. We found that AFP neurons in these isolate birds had highly tuned responses to isolate BOS. The selectivity was as high, and in the striato-pallidal nucleus Area X, even higher than that in normal birds, due to abnormally weak responsiveness to conspecific song. These results demonstrate that sensory learning of tutor song is not necessary for BOS tuning of AFP neurons. Because isolate birds develop their song via sensorimotor learning, our data further illustrate the importance of individual sensorimotor learning for song selectivity and provide insight into possible functions of song-selective neurons.