Supra second timing reflects oscillatory and aperiodic EEG dynamics

The perception of timing has been investigated across short and long timescales, with the latter usually underrepresented. Previous accounts of supra-second timing have often emphasised dedicated neural signals, yet whether timing performance over longer durations reflects specialised temporal mechanisms or domain-general neural excitability remains unclear. We examined this question in an interval reproduction task (2 to 4 s) using EEG, decomposing neural activity into oscillatory (alpha, theta) and aperiodic components and relating both to behavioural performance. At the neural level, separate analyses were performed on the interval encoding epoch and the following delay period. Time-resolved analyses revealed a coordinated decrease in posterior alpha power and aperiodic offset during interval encoding. In contrast, interval duration did not produce consistent modulation of oscillatory or aperiodic activity during the delay period, providing limited support for a workload-based account of time duration. Across participants, higher baseline alpha power and aperiodic offset were associated with better timing accuracy, whereas trial-by-trial fluctuations in aperiodic activity, and to a lesser extent alpha power, predicted single-trial reproductions. The results suggest that temporal behaviour in the supra-second range is shaped by domain-general neural activity sustaining goal-directed task engagement, with oscillatory and aperiodic dynamics serving as complementary indices of this broader excitability state.