# Low-frequency activity in the subthalamic nucleus informs about the acute neuropsychiatric state in Parkinson’s disease

## TL;DR

This study shows that brain activity in a specific region can reflect changes in mental state in Parkinson's patients, which could improve treatment strategies.

## Contribution

The study identifies low-frequency brain activity in the subthalamic nucleus as a potential biomarker for acute neuropsychiatric states in Parkinson’s disease.

## Key findings

- Elevated theta/low-alpha power in the subthalamic nucleus is linked to a low neuropsychiatric state in Parkinson’s patients.
- Neuropsychiatric state changes correlate with 6–8 Hz activity following medication intake in Parkinson’s patients.

## Abstract

Sensing-guided deep brain stimulation (DBS) offers potential to further optimize symptom control in Parkinson’s disease (PD) patients. Emerging evidence suggests that basal ganglia signals reflect not only motor, but also chronic neuropsychiatric symptoms. However, it remains unclear whether local field potentials (LFPs) can inform about acute neuropsychiatric states in PD, which we address in this work. Fourteen PD patients implanted with a brain-sense-enabled neurostimulator underwent an acute levodopa challenge OFF/ON stimulation one year after surgery. In each condition, resting state STN-LFPs were recorded, and the acute neuropsychiatric state was evaluated using the Neuropsychiatric Fluctuation Scale. The relationship between neuropsychiatric state and fluctuation scores with STN low-frequency activity (4–12 Hz) was assessed. An acute low neuropsychiatric state in the OFF-medication condition was associated with elevated theta/low-alpha power. Moreover, the 6–8 Hz activity was indicative of the neuropsychiatric state change following medication intake. Those results were most evident in recordings from the ventral contacts closer to the limbic STN, while chronic stimulation settings covering the dorsal associative and motor STN captured a similar trend. STN low-frequency activity may serve as a biomarker for the acute neuropsychiatric state and neuropsychiatric responsiveness to dopamine and may inform future sensing-guided DBS strategies.