The Temporal Constraints of the Cerebellum's Timekeeping
The cerebellum plays a central role in generating temporal predictions from past sensory regularities, yet the temporal boundaries of this predictive capacity remain unclear. Using magnetoencephalography (MEG), we investigated somatosensory and cerebellar responses to omissions within rhythmic somatosensory stimulation trains across six inter-stimulus intervals (ISIs) ranging from 0.5 to 5.5 seconds. We hypothesised that cerebellar prediction signals would follow a logistic decay pattern, remaining robust at short ISIs before declining beyond a 2-4-second temporal threshold. As a first step, we validated the omission paradigm by confirming the expected SI and SII response pattern to stimulations and the preservation of the SII response to omissions. Cerebellar source reconstruction revealed consistent beta band (14-30 Hz) responses to omissions peaking at 40-50 ms post-omission in right lobule VI, replicating previous findings. Critically, cerebellar activation to omissions was compatible with a logistic decay pattern with increasing ISI, with the inflexion point estimated within the hypothesised 2-4-second window, though precise localisation of this threshold warrants further investigation. Together, these findings establish empirical boundaries for cerebellar temporal prediction, suggesting that the cerebellum operates as a precise but duration-limited internal clock with implications for understanding the brains timing mechanisms and their functional consequences for perception.