Stop-related subthalamic beta activity indexes global motor suppression in Parkinson's disease.

Abstract

Rapid action stopping leads to global motor suppression. This is shown by studies using transcranial magnetic stimulation to measure corticospinal excitability of task-unrelated effectors (e.g., from the hand during speech stopping). We hypothesize that this global suppression relates to the STN of the basal ganglia. Several STN local field potential studies in PD patients have shown increased ß-band power during successful stopping. Here, we aimed to test whether this STN ß-band activity indexes global motor suppression measured by transcranial magnetic stimulation. We studied 9 medicated PD patients (age, 47-67 years; mean, 55.8; 3 female) who were implanted with STN-DBS electrodes. Participants performed a vocal stop-signal task (i.e., they had to occasionally stop a vocal response) while we simultaneously recorded local field potentials from right STN and delivered transcranial magnetic stimulation to primary motor cortex to measure corticospinal excitability from a task-unrelated hand muscle (first dorsal interosseous). Replicating previous results, STN ß-band power was increased (P < 0.005) and corticospinal excitability was reduced (P = 0.024; global motor suppression) during successful stopping. As hypothesized, global motor suppression was greater for successful stop trials with higher STN ß-power (median split: P = 0.043), which was further evident in a negative correlation between single-trial STN ß-power and corticospinal excitability (mean, r = -0.176; P = 0.011). These findings link stopping-related global motor suppression to STN ß-band activity through simultaneous recordings of STN and corticospinal excitability. The results support models of basal ganglia function that propose the STN has broad motor suppressive effects. © 2016 International Parkinson and Movement Disorder Society.