UC Berkeley

The zebra finch is a social songbird that lives in large groups and produces vocal communicationcalls to facilitate social interactions. A subset of these calls can be used for individual recognition, via distinct acoustic features that are stereotyped within a bird but individualized across birds. Given their large natural group sizes and the ethological importance of individual recognition, one might expect that zebra finches would have the capacity to recognize the calls of a large number of conspecifics. In this thesis, I describe a set of neuroethological experiments to test the memory of zebra finches for individual conspecifics by their vocalizations. We hypothesized that the caudal nidopallium (NCM), a higher-order auditory region of the avian brain analogous to mammalian auditory association cortex, is involved in the learning and retention of these auditory memories. Using an operant task in which birds were trained to associate the calls of some individuals with food reward, zebra finches were found to have a large capacity for recognizing individuals by their calls and song, and that those associations could be learned with just a few training examples and persist for at least a month without reinforcement. Furthermore, lesions to NCM eliminated previously formed associations but did not prevent re-learning or learning of novel stimuli, in contrast with lesions to vocal pre-motor pathways which had no effect on the recognition ability of the birds. Finally, using the spiking activity from single neurons across the cortical-like auditory regions of the brain, we found that familiar and task-relevant vocalizations elicited more reliable neural responses, with higher information capacity, than in response to unfamiliar and less behaviorally relevant calls.