Functional representation of learned communication signals in the songbird brain

Abstract

International audience

Birdsong, like speech, is a learned vocal behaviour whose development critically depends on social interactions. In highly social songbirds such as starlings, the lack of direct social contacts with adult conspecifics severely impacts the development of song behaviour. This raises the question of what functional representation of their vocalizations such deprived animals develop and what are the neural consequences of such abnormal development. We have recently observed, in the caudo-medial nidopallium (NCM) of adult male starlings, differential neuronal responses to distinct classes of sounds that have different functions and social values, and that are produced separately and differentially according to context. This suggests that this non-primary, associative auditory area that is analogous to the mammalian secondary auditory cortex could be the place for sorting sounds into functional categories in the songbird brain. Here we show that the development of these response properties is experience-dependent: young starlings that we raised without any direct contact with adults not only failed to differentiate starlings' typical song classes in their vocalizations but also failed to develop differential neural responses to these songs. The fact that song classes showing species-typical acoustic morphology were not differentiated in the experimental birds' vocalizations suggests that the observed deficit in neuronal responses to these song classes is likely to be linked to a failure to acquire songs' functions and may provide a model for abnormal development of communicative skills, including speech.