Pathological attenuation of the right prefrontal cortex activity predicts speech and limb motor timing disorder in Parkinson's disease.

Neurological deficits can cause a wide range of motor symptoms in patients with Parkinson's disease (PD). However, our understanding about the effects of PD on the underlying neural mechanisms of motor function has remained elusive. In the present study, we investigated the relationship between PD pathology and neurological deficits in planning and execution mechanisms of motor timing during speech production and limb movement. We used a combination of behavioral and event-related potential (ERP) measures to characterize motor timing deficits in patients with PD compared with a neurologically intact matched control group during randomized speech vowel vocalization and button press motor reaction time tasks in response to temporally predictable and unpredictable sensory stimuli. Behavioral results indicated slower motor reaction times in PD regardless of motor modality or temporal predictability of sensory stimuli. In addition, our analysis indicated that slower motor reaction times in PD were correlated with pathological attenuation of neural activities within the right precentral and inferior frontal cortex only before the onset of speech production and limb movement. These findings highlight the role of a right-lateralized prefrontal cortical network in motor planning and its relationship with PD pathology during speech and limb movement timing control. Based on these data, we suggest that pathological attenuation of neural activities within this network is a neurophysiological biomarker of general and modality non-specific motor timing deficits in PD. We propose that this right-lateralized prefrontal network is a potential candidate for targeted treatment of speech and limb motor timing disorders in patients with PD.