Subjective Beat Perception in Musical Rhythms in Adult Listeners

Synchronization to rhythmic stimuli is an everyday experience, whether it is exercising to the beat of music, dancing salsa, or rocking a baby to sleep. Commonly, humans synchronize their movements with the frequency of the beat (a quasi-isochronous pattern of prominent time points). Previous research has shown that the intended beat periodicity of a rhythmic stimulus can be observed in periodic neural activity; however, the extent to which this reflects robust perception of musical rhythm versus purely stimulus-driven activity is unknown. In Experiment 1 and 2, I investigated how long listeners can maintain a percept of the beat once the stimulus evidence becomes beat-ambiguous. In Experiment 3, I used electroencephalography (EEG) to investigate whether steady state-evoked potentials (SS-EPs, the electrocortical activity from a population of neurons resonating at the frequency of a periodic stimulus) arising from auditory cortex reflect beat perception when the physical information in the stimulus is ambiguous and supports two possible beat patterns. In both experiments, participants listened to a musical excerpt that strongly supported a particular beat pattern (context), followed by an ambiguous rhythm consistent with either beat pattern (ambiguous phase). During the final probe phase, listeners indicated whether a superimposed drum matched the beat. We found that participants perceived probes that matched the beat of the context as better fitting the ambiguous rhythm, compared to probes that did not match the beat of the context. We also found that SS-EPs during the ambiguous phase had higher amplitudes at frequencies corresponding to the beat of the preceding context. These findings support the idea that SS-EPs arising from auditory cortex reflect perception of musical rhythm and not just stimulus encoding of temporal features