Primate ACC encodes natural vocal interactions in a ‘cocktail party’

The Cocktail Party Problem (CPP)—extracting meaningful signals amid competing voices—remains poorly understood at the neural level, particularly in real-world contexts where it emerges naturally. We investigated the role of the anterior cingulate cortex (ACC) to resolve the CPP, a structure implicated in social monitoring but rarely examined in relation to audition, in freely-moving marmoset monkeys engaged in vocal exchanges with conspecifics in a noisy ecological environment. Analyses revealed that this neural substrate is seemingly integral to resolving the CPP. Not only did neurons encode the calls of either the conversational partner or background callers (i.e. figure/ground separation), but this selectivity persisted even with overlapping background sounds, a hallmark of the CPP. ACC was also sensitive to conversational dynamics by encoding turn-taking structure. These findings reveal that the ACC regulates dynamic vocal interactions in complex social soundscapes in which parsing meaningful calls from competing sounds is essential for effective communication.