Objectives/Aims To examine the causal role of the subthalamic nucleus (STN) in externally cued or internally generated decisions to execute or withhold an action by recording and stimulating neural activity in this region using deep brain stimulation (DBS) electrodes implanted for the treatment of Parkinson’s disease (PD).
Methods 20 PD patients completed an intentional inhibition task in which they were instructed by visual cues to go, stop or choose to go or stop. Each cue was on the screen until the patient pressed a button with their left thumb or for a maximum of 1500 ms and was preceded by a fixation cross for 1000–1500 ms. Local field potentials (LFP) were simultaneously recorded from the left STN and stimulated in the right STN at the clinical frequency of 130Hz or theta frequency 7Hz for 500 ms prior to the onset of the cue on half of the choice trials.
Results On non-stimulation choice trials, analysis of the LFP’s showed a significant decrease in theta activity when patients chose to stop compared to go. This difference began prior to the onset of the response. Behaviourally, patients chose to respond less when the STN was stimulated at a frequency of 7 hz for 500 ms prior to the onset of the cue but not at 130 Hz.On non-stimulation choice trials, analysis of the LFP’s also showed that there was a significant decrease in theta activity when patients chose to stop compared to go. This difference began prior to the onset of the response.
Conclusions The findings suggest that pre-existing theta activity in the STN may bias one’s pre-disposition to choose to initiate an action and that stimulation of this activity may interfere with this process.
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