Neural correlates of speech and limb motor timing deficits revealed by aberrant beta band desynchronization in Parkinson's disease.

Objective: We used a classical motor reaction time paradigm to examine the effects of Parkinson's disease (PD) on the mechanisms of speech production and upper limb movement.

Methods: Electro-encephalography (EEG) signals were recorded in PD and control groups during speech vowel production and button press tasks in response to temporally predictable and unpredictable visual stimuli.

Results: Motor reaction times were slower in PD vs. control group independent of stimulus timing and movement modality. This effect was accompanied by stronger desynchronizations of low beta (13-18 Hz) and high beta (18-25 Hz) band neural oscillations in PD vs. control prior to the onset of speech and hand movement. In addition, pre-movement desynchronization of beta band oscillations were correlated with motor reaction time in control subjects with faster responses associated with weaker beta band desynchronizations during the planning phase of movement. However, no such effect was found in the PD group.

Conclusions: We suggest that the aberrant pattern of beta band desynchronization is a neural correlate of speech and upper limb motor timing deficits as a result of cortico-striatal pathology in PD.

Significance: These findings motivate interventions targeted toward normalizing beta band activities for improving speech and upper limb movement timing in PD.