20 Hz beta stimulation of the subthalamic nucleus improves response inhibition in Parkinson's disease.

High-frequency deep brain stimulation of the subthalamic nucleus is used to treat motor symptoms in patients with Parkinson's disease. There is evidence that low-frequency stimulation in the range of 4-10 Hz may improve cognitive functions. This study investigates whether low-frequency deep brain stimulation of the subthalamic nucleus in the beta band (20 Hz) frequency can improve response inhibition in patients with Parkinson's disease. In a double-blind crossover design, N = 17 participants with Parkinson's disease performed four neuropsychological experiments, while on their usual dopaminergic medication, under no, standard high-frequency and 20 Hz beta low-frequency deep brain stimulation. The experiments consisted of a response selection task (response execution), a flanker task (conflict monitoring), a Go-NoGo task (automatic inhibition) and a stop-change task (controlled inhibition). Reaction time and response accuracy were analysed using Bayesian mixed-effect models. Participants responded [m = 33.6 ms, Bayes factor (BF) = 129.6] slower and [m = 6.0%, BF > 1000] more accurately under low-frequency than high-frequency stimulation but not under no stimulation during the response selection task. In the flanker task, participants responded slower under low-frequency than high-frequency stimulation [m = 77.0 ms, BF > 1000] but not under no stimulation [m = 18.3 ms, BF = 0.1]. We found no performance differences by the stimulation condition of the congruency effect. In the Go-NoGo task, we found low-frequency stimulation slowed responses on uncertain Go trials compared to no stimulation [m = 136.8 ms, BF = 30.3] and high-frequency stimulation [m = 105.2 ms, BF = 2.5]. Additionally, participants committed fewer errors under low-frequency stimulation than under no and high-frequency stimulation, suggesting that 20 Hz subthalamic nucleus stimulation may improve automatic inhibition. Lastly, in the stop-change task, we found no performance modulation by low-frequency stimulation compared to no and high-frequency stimulation. Our results show that low-frequency beta stimulation may improve aspects of automatic response inhibition in patients with Parkinson's disease.