Objective: To explore the subcortical neural correlates of impulse control and related behavioral disorders (ICBD) and trait impulsivity in a chronic and naturalistic setting in patients with Parkinson’s disease (PD).

Background: PD is associated with a range of neuropsychiatric manifestations which include ICBDs. These disorders represent a significant cause of reduced quality of life both for the patient and their families. A very limited number of studies have perioperatively identified subthalamic nucleus (STN) theta power as linked to ICBD and alpha power as linked to trait impulsivity, yet these signals have never been explored chronically in a naturalistic setting nor has the presence of similar signals in the globus pallidus internus (GPi) been explored.

Method: 13 patients (20 hemispheres) with Deep Brain Stimulation of either the STN or GPi were included in the study. Patients completed the Questionnaire for Impulsive-Compulsive Disorders in PD–Rating Scale (QUIP-RS) and the Barratt Impulsivity Scale (BIS-R21) at baseline. ‘Research’ and ‘OFF-med’ events were programmed via BrainSense (Percept PC) that would induce 30-second local field potential recordings. Patients performed 14 days of at-home recordings in which they triggered the ‘OFF-med’ event before taking their morning medication and the ‘research’ event while ON-medication twice per day (once stim on, once stim off). A linear mixed effects model was implemented for data analysis.

Results: Theta power in the ON-medication state was positively associated with ICBD regardless of stimulation setting (stim on p=0.040, stim off p=0.032). This relationship remained significant when nucleus, laterality, and levodopa equivalent daily dose were included in the model. OFF-med theta power was not significantly related to ICBD (p=0.274). Trait impulsivity and theta power were positively correlated in the OFF-med state (p=0.003), but not in the ON-med state (on stim p=0.990, off stim p=0.678). Alpha power was not related to ICBD or impulsivity in either medication state.

Conclusion: Chronically recorded higher theta power in the ON-medication state correlated with higher ICBD scores and in the OFF-medication state correlated with higher trait impulsivity. This relationship is present in both the STN and the GPi. Theta power may therefore prove to be a viable electrophysiological biomarker for detecting underlying ICBD in patients with PD.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/exploring-the-neural-correlates-of-impulsivity-and-impulsive-compulsive-behaviors-in-parkinsons-disease/