Poster B125, Sunday, March 26, 8:00 – 10:00 am, Pacific Concourse
Neural correlates of guided and unguided motor timing in Parkinson’s disease
Klara Hagelweide1,2, Ellen Binder2, Katja Kornysheva3, Esther A. Pelzer2,4, Marc Tittgemeyer4, Gereon R. Fink2,5, Ricarda I. Schubotz1,2; 1University of Muenster, Germany, 2University Hospital Cologne, Germany, 3University College London, Great Britain, 4Max Planck Institute for Metabolism Research, Cologne, Germany, 5Research Centre Jülich, Germany
The cortico-basal ganglia-thalamo-cortical loop connecting the putamen to the supplementary motor area plays an important role in motor timing. As dopaminergic depletion disrupts this motor loop, patients suffering from Parkinson’s disease (PD) show behavioral deficits and motor loop hypoactivity when tapping in synchronization to a pacing signal. This impairment is increased when tapping is continued without pacing signal and accompanied by compensatory hyperactivity in cerebellum, lateral premotor cortex and prefrontal areas. To disentangle the influence of lacking external guidance from memory-driven time interval production, we extended the classical synchronization – continuation paradigm with a free tapping condition which required tapping at a self-chosen interval. Using this paradigm we measured fourteen PD patients (8 male) ‘on’ and ‘off’ medication and fourteen healthy control participants matched for gender and age in an fMRI study. As hypothesized, patients showed poorer tapping performance compared to healthy controls and ‘off’ compared to ‘on’ medication accompanied by less activity in the motor loop. Interestingly, the expected hyperactivity in cerebellum and lateral premotor cortex in patients was only observed during continued tapping. As tapping deficits were not more pronounced during continuation or free tapping than in synchronization trials, the observed hyperactivity probably reflects a compensatory mechanism not used during free tapping. Instead, in free trials there was a tendency to more negative asynchrony ‘off’ compared to ‘on’ medication, possibly showing that the production of an externally given time interval implies more compensational resources than the production of a self-chosen interval.
Topic Area: PERCEPTION & ACTION: Motor control