Synchronization to auditory and visual beats in Parkinson's disease.

The ability to move in synchrony with a perceived regular beat in time is essential for humans to interact with environments in an anticipatory manner, and the basal ganglia have been shown to be preferentially involved in beat processing. Auditory beats are often adopted in assessing the sensorimotor deficiency of patients with Parkinson's disease (PD), which is characterized by basal ganglia dysfunction. Whereas beat synchronization has long been considered to be specific to the auditory modality, recent studies employing moving instead of static visual stimuli have shown comparable synchronization performances of auditory and visual beats. Here, we show that compared with control subjects, synchronization stability of PD patients significantly decreased for beats composed of visual contracting rings but not for beats consisting of auditory tones or static visual flashes. The results revealed specific impairment of visual beat synchronization in PD. Considering the common experience of visuomotor interactions in daily lives of PD patients, the present finding emphasizes the importance of evaluation of visuomotor timing deficiency in PD by employing moving visual stimuli that have ecological relevance.