Effects of Excitatory and Inhibitory LIFUS of GPi in Parkinsonian Patients Without DBS

The goal of this study is to evaluate the effects of two different deep brain LIFUS protocols on task performance in PD patients. We will use two different protocols (5 Hz theta Burst vs 10 Hz inhibitory), bilaterally on the GPi of PD patients in two different sessions and evaluate their performance in visuomotor tasks using stop signal paradigm. We will also use active sham in a separate session bilaterally on the occipital cortex, more specifically Brodmann area 19 to compare differences in tremor activity. We will record behavioral performance of the patients to disentangle effects of different TUS protocols on PD patients. We will also use finger accelerometer on the tremor dominant hand, to evaluate possible changes in tremor.

For each participant, there will be four visits. In the first visit, a structural MRI scan will be obtained. In the subsequent three visits, the LIFUS experiments including the behavioral tasks on the computer, UPDRS motor scoring, and finger accelerometry recordings will be conducted in random order. In these visits, the task performance (stop-signal task) will be recorded before and after applying the 3 different LIFUS paradigms: 1) theta burst TUS of the GPi in one session, 2) 10Hz TUS of the GPi in one session, and 3) active sham condition in the occipital cortex (bilateral) where we will use theta burst LIFUS to the Brodmann area 19 at a TPO distance of ~30mm. Visits 2, 3, and 4 will be separated by at least 1 week each and theta burst TUS (2 minutes x2 =4 min), 10 Hz protocol (Burst length 30ms, period 1000, 30% dc. Total Time: 40 seconds x2= 80 seconds) and sham theta bust TUS will be tested in random order.