Individual vocal recognition and the effect of partial lesions to HVc on discrimination, learning, and categorization of conspecific song in adult songbirds

Among songbirds, the capacity to associate particular songs with particular singers (i.e., vocal recognition) forms the cognitive basis for more complex communication behaviors such as female choice and territoriality. In the present study, we combine operant conditioning techniques and excitotoxic lesions to the forebrain nucleus HVc to examine the role of this region in the discrimination, associative learning, and categorization of conspecific song. We trained adult male and female European starlings, Sturnus vulgaris, to recognize simultaneously the songs of several conspecific males. Then, using a series of transfer procedures, we demonstrate that correct recognition does not generalize to song bouts containing novel motifs from familiar singers. This suggests that starlings do not make use of individually invariant source or filter characteristics for vocal recognition. We then lesioned a portion of HVc bilaterally with ibotenic acid, and exposed the birds to a series of manipulations testing the discrimination, associative learning, and categorization of conspecific song. The lesions attenuated song production among males, but retention of the basic recognition task (i.e., maintenance of the discrimination) was unaffected. However, when the response contingencies were reversed-as a test of associative learning independent of discrimination-the initial performance and subsequent learning rate were negatively correlated with the size of the HVc lesions. This suggests that HVc plays a role in the formation of associations between a song and some referent. The results of this study are discussed in light of earlier claims regarding the role of HVc in the perceptual processing of conspecific song.