The presence of an audience modulates responses to familiar call stimuli in the male zebra finch forebrain.

The ability to recognize familiar individuals is crucial for establishing social relationships. The zebra finch, a highly social songbird species that forms lifelong pair bonds, uses a vocalization, the distance call, to identify its mate. However, in males, this ability depends on social conditions, requiring the presence of an audience. To evaluate whether the presence of bystanders modulates the auditory processing underlying recognition abilities, we assessed, by using a lightweight telemetry system, whether electrophysiological responses driven by familiar and unfamiliar female calls in a high-level auditory area [the caudomedial nidopallium (NCM)] were modulated by the presence of conspecific males. Males had experienced the call of their mate for several months and the call of a familiar female for several days. When they were exposed to female calls in the presence of two male conspecifics, NCM neurons showed greater responses to the playback of familiar female calls, including the mate's call, than to unfamiliar ones. In contrast, no such discrimination was observed in males when they were alone or when call-evoked responses were collected under anaesthesia. Together, these results suggest that NCM neuronal activity is profoundly influenced by social conditions, providing new evidence that the properties of NCM neurons are not simply determined by the acoustic structure of auditory stimuli. They also show that neurons in the NCM form part of a network that can be shaped by experience and that probably plays an important role in the emergence of communication sound recognition.