Rhythmic Entrainment Echoes in Auditory Perception

Rhythmic entrainment echoes – rhythmic brain responses that outlast rhythmic stimulation – can evidence endogenous neural oscillations entrained by the stimulus rhythm. We here tested for such echoes in auditory perception. Participants detected a pure tone target, presented at a variable delay after another pure tone that was rhythmically modulated in amplitude. In four experiments involving 154 participants, we tested (1) which stimulus rate produces the strongest entrainment echo and (2) – inspired by audition’s tonotopical organisation and findings in non-human primates – whether these are organized according to sound frequency. We found strongest entrainment echoes after 6-Hz and 8-Hz stimulation, respectively. Best moments for target detection (in or in anti-phase with the preceding rhythm) depended on whether sound frequencies of entraining and target stimuli matched, in line with a tonotopical organisation. However, for the same experimental condition, best moments were not always consistent across experiments. We provide a speculative explanation for these differences that relies on the notion that neural entrainment and repetition-related adaptation might exercise competing, opposite influences on perception. Together, we find rhythmic echoes in auditory perception that seem more complex than those predicted from initial theories of neural entrainment.