Delta Oscillations in Human Communication.

Slow brain oscillations in the delta-band (0.5 - 4Hz) may play an important role in social interactions, given available evidence across areas of perception, action and social neuroscience. The aim of this review is to theoretically integrate empirical evidence related to intra- and inter-brain delta-band rhythms under a social cognition umbrella, proposing that delta oscillations provide a temporal scaffold for human communication. In the first part we synthesise evidence related to intra-brain activity, highlighting that the delta-band aligns to the timing of verbal communication and speech rhythm. Beyond speech, delta-band activity has been reliably associated with emotion processing, as well as social and movement perception, all of which support nonverbal communication. Moreover, delta-band activity is linked to event expectation across modalities including rhythm and groove perception. In the second part we discuss recent interpersonal neural synchrony (INS) evidence showing that delta-band activity is linked to social interaction, particularly cooperation, and modulated by individual differences. In naturalistic settings, delta-band INS is associated with verbal and nonverbal communication. Linking the cognitive neuroscience of communication to engagement with the performing arts, we review relevant evidence reporting delta-band INS in music and dance. We discuss a social function of slow wave brain activity in the context of an ongoing debate about the origins of rhythmical brain activity and INS. Finally, we outline research questions that may provide a greater empirical footing in support of a putative role of delta oscillations for human communication.