Electrophysiological signature of explicit and implicit timing

Abstract

Temporal processing in the millisecond-to-seconds range underpins many cognitive and motor functions and can be engaged either explicitly or implicitly. Yet, the neural mechanisms distinguishing explicit and implicit timing remain debated. This study aimed to directly compare the electrophysiological (EEG) correlates of explicit and implicit timing. Participants performed an explicit timing task (time bisection task) and an implicit timing task (foreperiod task), matched for sensory and response demands. Analyses focused on early event-related potentials (N1/P2 complex), the Contingent Negative Variation (CNV), and beta-band oscillatory activity, all time-locked to cue onset and associated with anticipatory processes. Behavioural results confirmed robust foreperiod effects in implicit timing and accurate temporal discrimination in explicit timing. EEG results revealed larger N1/P2 and CNV amplitudes in the implicit timing task, particularly for longer intervals, suggesting greater expectation processes and motor preparatory demands. Time-frequency analyses showed stronger beta desynchronization during implicit timing. Furthermore, both N1/P2 and CNV amplitudes predicted behavioural performance across tasks, with CNV correlating more with sensitivity than perceived duration. These findings support largely overlapping neural dynamics for explicit and implicit timing with a prominent role of expectation and motor preparation processes, especially under implicit temporal task demands.