Signatures of time interval reproduction in the human electroencephalogram (EEG)

Accurate timing is essential for coordinating our actions in everyday tasks such as playing music and sport. Although an extensive body of research has examined the human electrophysiological signatures underpinning timing, the specific dynamics of these signals remain unclear. Here, we recorded electroencephalography (EEG) while participants performed a variant of a time interval reproduction task that has previously been administered to macaques, and examined how task performance was predicted by the dynamics of three well-known EEG signals: limb-selective motor preparation in the mu/beta band (8-30 Hz), the Contingent Negative Variation (CNV), and the Centro-Parietal Positivity (CPP) evidence accumulation signal. In close correspondence with single unit recordings in macaques, contralateral mu/beta signals indicated that participants reproduced intervals by adjusting the starting level and build-up rate of motor preparation to reach a response triggering threshold at the desired time. The CNV showed a highly similar pattern with the exception that its pre-response amplitude was increased for faster reproductions. This pattern of results suggests that, rather than tracing a veridical temporal accumulator as had been suggested in earlier work, the CNV more closely resembles a dynamic anticipatory signal. In contrast, the CPP did not exhibit any relationship with reproduction time, suggesting that the evidence accumulation processes guiding perceptual decisions are not involved in generating representations of elapsed time. Our findings highlight close similarities in the dynamics exhibited by intracranial and non-invasive motor preparation signals during interval reproduction while indicating that the CNV traces a functionally distinct process whose precise role remains to be understood.