Response inhibition as measured during a stop-signal task refers to the ability to halt an action that has already been set in motion. Cortical and sub-cortical structures, such as the subthalamic nucleus (STN), that are active during attempts to inhibit action are thought to contribute to a 'stop-process' that must gain dominance over a 'go-process' if inhibition is to be successful. We recorded local field potential activity from the STN of Parkinson's disease patients with implanted deep brain stimulation electrodes during a stop-signal task. In particular we measured activity in the STN that has traditionally been associated with motor action (gamma-band, 60-100 Hz) and inhibition (beta-band, 10-30 Hz). Our data support the idea that beta activity in the STN is related to the inhibition of motor action. Further, we report that gamma oscillatory activity responds robustly to stop-signals as well as go-signals. This unexpected finding might suggest that gamma activity supports a go-process that not only responds to go-signals, but is also sensitive to stimuli that signal stopping.
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