Turn-taking and the rapid adaptation of an individual’s actions to respond appropriately to those of their social partner are key components of many social interactions, including human conversation. Okobi, Banerjee et al. now demonstrate the role of the motor cortex in the precise timing of complex acoustic exchanges in ‘singing’ mice.

Credit: Jennie Vallis/Springer Nature Limited

Our understanding of the neural basis of human social exchange has been limited, in part, by the scarcity of animal models that can mimic the features and complexities of human conversation. The authors here propose a new rodent model of vocal communication: Alston’s singing mouse is a native of Central American cloud forests that communicates with its social partners through a rapid exchange of ‘songs’, the timing of which resembles human conversation.

The authors found that the acoustic characteristics of the songs produced by an individual mouse were highly stereotyped when recorded in isolation. However, when the same mouse (the ‘recruit’) was transferred into a room in which they could hear, but not see, a ‘resident’ mouse, it sang more often and its songs were more variable. Moreover, in order to engage in coordinated turn-taking, the recruit mice were able to precisely start and stop their songs to avoid overlap with the resident’s songs.

The authors next sought to identify the neural mechanisms responsible for such ‘countersinging’ and found that intracortical microstimulation of the orofacial motor cortex (OMC) activated the jaw muscles involved in song production. Thermoelectric cooling of the OMC slowed cortical dynamics and led to prolonged songs without dilating individual notes. Furthermore, electrical stimulation of this region briefly ‘paused’ spontaneous singing, with mice picking up at the point in the song sequence at which they had stopped when the stimulation was removed.

These findings indicated that the OMC controls the timing of singing rather than the song structure, which may be generated by subcortical circuits. This suggests that the OMC might contribute to the effects of social interaction on song timing. Indeed, the authors found that muscimol-induced inhibition of the OMC reduced responses to playback of a conspecific mouse’s song.

Alston’s singing mouse … communicates with its social partners through a rapid exchange of ‘songs’, the timing of which resembles human conversation

This study provides evidence for an executive role of the motor cortex in the rapid and precise control of vocal responses, enabling social exchange. Comparative studies are required to determine whether similar control mechanisms operate in humans; however, the authors speculate that the singing mouse model might provide information relevant to the study of disorders in which communication is affected, such as autism or stroke.