Presentation Information
[P1-05]Temporally distorted cortical neural dynamics of explicit timing following cerebellar dysfunction
*Chiara Zanonato1,2, Richard Ivry3,4, Assaf Breska1,3 (1. Max Planck Institute for Biological Cybernetics, Tübingen (Germany), 2. University of Tübingen (Germany), 3. Department of Psychology, University of California, Berkeley, CA (United States of America), 4. Helen Willis Neuroscience Institute, University of California, Berkeley, CA (United States of America))
Keywords:
explicit timing,interval timing,cerebellum,cerebellar ataxia,EEG
The ability to quantify temporal intervals, known as explicit timing, relies on a distributed brain network, with the cerebellum playing a key role, as suggested by brain stimulation and neuropsychology studies. Yet, how the cerebellum impacts cortical dynamics of explicit timing, and at which stage of temporal information processing, remains unexplored. Here, we addressed this using scalp electroencephalography (EEG) in cerebellar ataxia (CA) patients (N=15) and healthy controls (N=10) performing a temporal discrimination task. In separate blocks, participants judged whether the duration of a fixed standard (700ms or 1200ms) matched or differed from that of a subsequent comparison spanning between the short and long standard durations. This design allowed us to dissociate comparison judgments anchored to the standard from those anchored to the comparison set’s bisection point (BP). Behaviorally, temporal sensitivity was reduced in patients, replicating previous studies. Neurally, during the comparison interval, the contingent negative variation (CNV) potential failed to show adjusted ramping based on the standard interval in both groups. Instead, the CNV in controls peaked at the BP and resolved afterwards, in line with a BP mechanism. Conversely, in CA patients, it continued ramping negatively beyond the BP, indicating a lack of sensitivity to this anchor. Analysis of delta-band activity (0.54-2.18Hz) phase dynamics in the same time period revealed increased phase alignment before the earliest possible comparison in both groups. However, this was stronger in controls than in patients, consistent with previous findings in implicit timing. Importantly, evoked responses to standard onset were comparable between groups, ruling out group differences due to noisy or generally reduced brain responsivity in patients. Overall, these results uncover the cerebellar role in shaping cortical dynamics of explicit timing, specifically through the adjustment of anchor-dependent anticipatory activity