Subthalamic nucleus stimulation effects on single and combined task performance in Parkinson's disease patients: a PET study

Subthalamic nucleus deep brain stimulation (STN-DBS) represents one of the most efficacious treatments for Parkinson's disease, along with L-dopa therapy. The objective of the present work was to identify the cerebral networks associated with hand movement and speech production tasks performed alone and simultaneously, as well as the effects of STN-DBS on these profiles. Clinical, behavioral, and neuroimaging (oxygen 15-labeled water and Positron Emission Tomography) investigations were used to study single and combined performances of unilateral hand movements and speech production in 11 unmedicated individuals with PD, both off and on STN-DBS. Specifically, a flexible factorial design with the tasks (hand movement, speech production, combined task) and the STN-DBS conditions (off, on) as main factors was chosen for brain activation statistical analysis, using a Family-Wise Error corrected p-value at the cluster level of at least 10 contiguous voxels. Increased activation of fronto-parietal and cingulate areas was observed under STN-DBS for hand movement in single and combined tasks, respectively, reflecting a partial restoration of cortico-sub-cortical connections. The lack of results for speech production for both off and on STN-DBS could illustrate its relatively poor response to the treatment. STN-DBS tended to restore the additive function capacity that can be achieved when performing the combined task. We confirmed with original neuroimaging data that speech is much less responsive to STN-DBS than any other motor function and we concluded that speech outcomes following STN-DBS can be different from those observed pre-operatively following L-dopa administration.