Subthalamic nucleus oscillations correlate with vulnerability to freezing of gait in patients with Parkinson's disease

Freezing of gait (FOG) is a debilitating symptom in advanced Parkinson's disease, yet its underlying neural mechanisms remain poorly understood. This study investigates whether specific oscillatory activities within the subthalamic nucleus (STN)—a key target for deep brain stimulation—correlate with a patient's susceptibility to freezing during walking tasks.

The researchers recorded local field potentials (LFP) from the STN of 15 patients with Parkinson's disease while they performed single-task (ST) and dual-task (DT) walking. To objectively quantify gait vulnerability, the team used an index of freezing (iFOG) derived from trunk accelerometry. This index allowed the researchers to compare neural activity during periods of normal gait versus periods where the gait was more susceptible to freezing, even in the absence of full-blown freezing episodes.

The study identified two distinct spectral signatures associated with increased FOG vulnerability. First, low beta band power (15–21 Hz) was consistently elevated during periods of higher FOG vulnerability across both single-task and dual-task conditions. Second, theta band power (5–8 Hz) also increased during vulnerable gait. While the low beta elevation was distributed across the STN, the theta band increase was more focal, appearing primarily in the ventral STN and the substantia nigra (SNr) during single-task walking. These findings suggest that specific narrow-band oscillations in the STN area serve as physiological markers for the state of being vulnerable to freezing.

These results provide new evidence linking specific STN oscillations to the pathophysiology of FOG. By identifying these biomarkers, the study opens the door for the development of adaptive deep brain stimulation (aDBS) systems. Such systems could potentially deliver stimulation on-demand, triggering only when these specific oscillatory patterns are detected, thereby offering a more personalized and effective treatment for patients suffering from freezing.