Lateralization of social signal brain processing correlates with the degree of social integration in a songbird

Group cohesion relies on the ability of its members to process social signals. Songbirds provide a unique model to investigate links between group functioning and brain processing of social acoustic signals. In the present study, we performed both behavioral observations of social relationships within a group of starlings and individual electrophysiological recordings of HVC neuronal activity during the broadcast of either familiar or unfamiliar individual songs. This allowed us to evaluate and compare preferred partnerships and individual electrophysiological profiles. The electrophysiological results revealed asymmetric neuronal activity in the HVC and higher responsiveness to familiar than to unfamiliar songs. However, most importantly, we found a correlation between strength of cerebral asymmetry and social integration in the group: the more preferred partners a bird had, the more its HVC neuronal activity was lateralized. Laterality is likely to give advantages in terms of survival. Our results suggest that these include social skill advantages. Better knowledge of links between social integration and lateralization of social signal processing should help understand why and how lateralization has evolved.