Investigating LFP Correlates of TUS in Patients With Movement Disorders (TUS-LFP)

Investigating Local Field Potential Correlates of Transcranial Ultrasound Stimulation in Patients With Movement Disorders

Transcranial Ultrasound Stimulation (TUS) is an emerging non-invasive brain stimulation(NIBS) technique that can be used on both superficial and deep brain targets with a high spatial resolution as small as a few cubic millimeters. Neural correlates of TUS have yet been elucidated. To date, no intracranial recordings (i.e., local field potential [LFP]) have been captured during or after TUS in patients with movement disorders. In this study, we are aiming to profile basal ganglia LFP activity during and after TUS by using a DBS system that is capable of recording LFP. This can shed light on mechanisms of TUS, as well as allow identification of a neurophysiological biomarker that can be used to tune the TUS sonication parameters for future clinical trials.

Experiment 1: Subjects will be randomly assigned to either the sham or active stimulation group during the first study visit. In the second study visit, there will be a crossover between the groups, with all subjects undergoing one sham and one active stimulation visit before the study is completed. During the active stimulation visit, a theta burst protocol (Isppa: 30 W/cm2, burst length: 20 ms, period: 200 ms, frequency 500 kHz) will be used to sonicate the bilateral primary motor cortices (M1) or globus pallidus interna (GPi) for 2 minutes. The sham group involves sonications performed with the power set to 0 watts over bilateral M1s/GPis. In both groups, the subjects will be masked using white noise transmitted through earbuds. The targets will be identified anatomically using structural MRIs and a neuronavigation system. The Percept PC DBS system will be used to record local field potentials (LFPs) from the subthalamic nucleus (STN) or globus pallidus internus (GPI) at various time points: before (baseline) and during the sonications, as well as at 10-, 30-, and 45-minute intervals after the sonications. These recordings will be obtained while the subjects engage in a finger tapping task monitored by an accelerometer, as well as during resting periods. The power of LFPs across different frequencies will be compared and correlated with the velocity observed during the finger tapping task. Following the completion of sham and active stimulation visits, the subjects will have the opportunity to participate in an optional control group visit, which entails sonication of the occipital cortex utilizing the theta burst protocol. Experiment 2: TUS will be utilized to target the area directly over the DBS lead, while concurrently recording LFPs to identify any stimulation artifact indicative of target area-sonication engagement.

The subject will be blind to stimulation condition (sham/active TUS). The assessor will be blind to stimulation condition (sham/active TUS) while analyzing LFPs. The UPDRS examination will be video-recorded and blindly assessed by a research team member.

NeuroFUS device stimulation with 4 channel transducer Stimulation target = M1/GPi Stimulation parameters = Theta burst protocol and 30 Watts

NeuroFUS device stimulation with 4 channel transducer Stimulation target = M1/GPi Stimulation parameters = Theta burst protocol and 0 Watts

Bilateral M1s/GPis will be sonicated using NeuroFUS device for two minutes per hemisphere with theta burst protocol and 30 W/cm2 Isppa

Bilateral M1s/GPis will be sonicated using NeuroFUS device for two minutes per hemisphere with theta burst protocol and 0 W/cm2 Isppa

5 minutes long recordings during both study visits at 1) Baseline (20-30 minutes before sonication), 2) during sonication, 3) 10 minutes after sonication, 4) 30 minutes after sonication, and 5) 45 minutes after sonication

Two assessments will be conducted during each study visit: one at baseline (within the first minute of the study) and the other upon completion of the study visit (between 120 and 130 minutes after the study visit initiation).

Correlation of LFP power change with the velocity change during finger tapping task as recorded by an accelerometer

LFPs during finger tapping will be recorded at each visit for half minute at 1) Baseline (20-30 minutes before sonication), 2) 10 minutes after sonication, 3) 30 minutes after sonication, and 4) 45 minutes after sonication

Inclusion Criteria: Adult patients with movement disorders (diagnosed by a movement disorder specialist) Implantation of a Percept PC DBS system at least one month before the sonications Stable dopaminergic medication dose for a minimum of 4 weeks Exclusion Criteria: Concomitant neurological conditions (stroke, seizure, dementia, major depression / psychiatric disorders, active drug abuse/addiction and major neuromuscular/musculoskeletal diseases) Declined cognitive scores (MoCA score < 22) Implants (cardiac pacemaker, implantable cardioverter-defibrillator, intracranial devices other than DBS system such as shunts and MR-unsafe devices) History of intracranial lesioning procedures Major systemic illness, infection or pregnancy