Neural tracking at theta predicts drumming-induced altered states of consciousness

Altered states of consciousness (ASC) involve shifts in perception, cognition, and awareness, offering a unique lens on the nature of consciousness. Across cultures, rhythmic drumming in the theta range (4-7 Hz) is often used to induce such states, but it remains unclear whether actively enhancing brain rhythms in this range can cause ASC. We tested whether theta-frequency drumming (4 beats per second) selectively induces ASC compared to rhythms in the delta and alpha ranges. Forty participants listened to ten-minute drumming sessions at each rhythm while EEG was recorded. After each session, they completed an altered experience questionnaire and a time estimation task - an implicit ASC measure. Rhythmic neural tracking at theta was linked to stronger altered experience. Furthermore, participants with stronger theta-band neural tracking to 4-bps drumming tended to report higher ASC across all drumming rhythms, suggesting that neural tracking at this rhythm might serve as a neural marker of susceptibility. These rhythm-specific effects indicate a bidirectional relationship between theta activity and ASC: not only do theta activity accompany ASC, it may actively modulate it. These findings shed new light on the neural dynamics of consciousness and suggest that rhythmic stimulation could serve as a non-pharmacological method for modulating conscious states, with potential applications in cognitive neuroscience and therapeutic contexts.