Slow-delta phase concentration marks improved temporal expectations based on the passage of time.

Temporal expectations enhance neural encoding precision, reflected in optimized alignment of slow neural oscillatory phase, and facilitate subsequent stimulus processing. If an event's exact occurrence time is unknown, temporal expectations arise solely from the passage of time. Here, we show that this specific type of temporal expectation is also reflected in neural phase organization. While undergoing magnetoencephalography, participants performed an auditory-delayed matching-to-sample task with two syllables (S1, S2). Critically, S1-onset time varied in the 0.6-1.8-s (i.e., 0.6-1.7 Hz) range. Increasing S1-onset times led to increased slow-delta (0.6-0.9 Hz) phase coherence over right frontotemporal sensors during S1 encoding. Moreover, individuals with higher slow-delta coherence showed decreased alpha power (8-13 Hz) during subsequent memory retention. In sum, temporal expectations based on the passage of time optimize the precise alignment of neural oscillatory phase with an expected stimulus.