A silent disco: Persistent entrainment of low-frequency neural oscillations underlies beat-based, but not memory-based temporal expectations
AbstractTemporal expectations (e.g., predicting “when”) facilitate sensory processing, and are suggested to rely on entrainment of low frequency neural oscillations to regular rhythmic input. However, temporal expectations can be formed not only in response to a regular beat, such as in music (“beat-based” expectations), but also based on a predictable pattern of temporal intervals of different durations (“memory-based” expectations). Here, we examined the neural mechanisms underlying beat-based and memory-based expectations, by assessing EEG activity and behavioral responses during silent periods following rhythmic auditory sequences that allowed for beat-based or memory-based expectations, or had random timing. In Experiment 1 (N = 32), participants rated how well probe tones at various time points fitted the previous rhythm. Beat-based expectations affected fitness ratings for at least two beat-cycles, while the effects of memory-based expectations subsided after the first expected time point in the silence window. In Experiment 2 (N = 27), using EEG, we found a CNV following the final tones of memory-based and random, but not beat-based sequences, suggesting that climbing neuronal activity may specifically reflect memory-based expectations. Moreover, we found enhanced power in the EEG signal at the beat frequency for beat-based sequences both during listening and the silence. For memory-based sequences, we found enhanced power at a frequency inherent to the memory-based pattern only during listening, but not during the silence, suggesting that ongoing entrainment of low frequency oscillations may be specific to beat-based expectations. Finally, using multivariate pattern decoding on the raw EEG data, we could classify above chance from the silence which type of sequence participants had heard before. Together, our results suggest that beat-based and memory-based expectations rely on entrainment and climbing neuronal activity, respectively.
