The effect of stimulus type and tempo on sensorimotor synchronization during finger-tapping in cerebellar ataxia: Behavioral and neural evidence

Sensorimotor synchronization, coordination of movements with external rhythms, occurs daily. Finger-tapping tasks are often used to study biological mechanisms underlying sensorimotor synchronization. This study investigates how deviations in auditory stimulus tempo from spontaneous motor tempo affect sensorimotor synchronization in patients with cerebellar ataxia during active listening and finger-tapping. Specifically, the cerebellum's role in these tasks is investigated by quantifying behavioral and neural dynamics of auditory-motor coupling. Sixteen patients with cerebellar ataxia and 14 healthy controls listened and tapped to music and metronomes at seven tempi (-12%, -8%, -4%, 0%, +4%, +8%, +12% of spontaneous tapping tempo) in randomized order. Sixty-four channel EEG, stimulus beat- and finger-tapping onsets were recorded during each trial. Behavioral synchronization was quantified by synchronization precision and accuracy, whereas neural entrainment was quantified with the stability index. Cerebellar patients displayed higher, more variable spontaneous tapping tempi than controls. Although precision was lower in patients than controls, they achieved high precision values. Differences in synchronizing between metronomes and music were observed for both precision and accuracy, favoring metronomes in both groups. Accuracy was impacted, with lowest asynchrony observed in patients with music, and across groups at the slowest tempi (-12%) and highest tempi (4, 8 and 10%). EEG results revealed greater stability for music during tapping. Although patients with cerebellar ataxia showed synchronization deficits, they could sufficiently synchronize with isochronous metronomes and music containing higher complexity, likely through sensory accumulation as a compensation strategy. These findings support the use of sensorimotor synchronization strategies in rehabilitation for cerebellar disorders.