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Abstract

Humans keep track of temporal intervals for different goals, from explicitly reporting perceived magnitudes to implicitly orienting attention in time. Whether overlapping or segregated timing mechanisms subserve these timing processes is a key neuroscientific question. Neuroimaging studies revealed goal-dependent functional dissociations, mostly at the cortical level. However, recent behavioral work hints to computational overlap. Moreover, separate lines of research have implicated the cerebellum in both explicit and implicit interval timing, but whether this reflects one shared or two context-specific cerebellar mechanisms is unknown. Here, we investigated how the cerebellum might act as a central timing circuit in both tasks and causally control cortical neural dynamics. Cerebellar Ataxia (CA) patients (N=20) and age-matched neurotypical controls (N=12) performed explicit (temporal discrimination) and implicit (temporally cued speeded detection) interval timing tasks while recording scalp EEG. Two intervals (S1, S2) were sequentially presented: S1 was either short (700ms) or long (1200ms), while S2 spanned between the short and long S1. Behaviorally, CA patients were impaired compared to healthy controls in both tasks, showing lower temporal sensitivity in temporal discrimination and smaller validity effect in temporal orienting. Critically, the degree of impairment significantly correlated in the patient group when S1 was short. Moreover, EEG analysis revealed that S1-dependent adjustment of proactive ramping activity (i.e. CNV potential) was abolished in patients in explicit timing, mirroring previous findings in implicit timing. These findings point towards the cerebellum as a central sub-second interval timing hub, affecting the encoding of intervals independently of the final timing purpose.