New insights into the auditory processing of communicative signals in the HVC of awake songbirds

In the present study, using a systematic recording method and a variety of stimuli, we determined the proportion of responsive sites and their response features in the vocal control nucleus HVC of awake-restrained starlings, a species with multiple song types. Responsive sites were classified into three groups, according to the number of stimuli to which they responded. Sites in the three groups showed responses to individual-specific songs, with sites in the group that showed responses to only one stimulus responding mostly to a bird's own song. In comparison, very few sites exhibited responses to universal species-specific songs and to artificial nonspecific sounds. By contrast, data obtained in the same birds under urethane anesthesia show that, although the total proportion of responsive sites was similar, numerous responses to a universal species-specific song and to an artificial nonspecific pure tone could be observed.