Objective: Examine dorsal and ventral STN subregion’s roles in motor conflict with intraoperative recordings during the implantation of a DBS device in Parkinson’s disease (PD) patients.

Background: Deep Brain Stimulation (DBS) of the dorsal motor region of the subthalamic nucleus (STN) is an effective treatment to reduce clinical motor symptoms in PD. However, DBS has adverse cognitive side effects, potentially caused by stimulation in the ventral (limbic) subregion of the STN. The dorsal and ventral STN subregions receive dissociable inputs from pre-frontal/motor and limbic regions, evidence of distinct roles. This study used a frequency analysis (local field potentials) to detect and understand the segregation of function within the STN, during the performance of an action conflict task. We predicted increased conflict-related activity in the theta band in the dorsal relative to the ventral STN.

Method: Eight individuals completed an intraoperative Simon conflict task. The Simon task requires a directional response to the color of a spatially lateralized stimulus. A conflict is induced when the action signaled by the spatial location and color are not the same, and the inappropriate action impulse must be suppressed. During the task microelectrodes in STN (dorsal than ventral regions) continuously recorded activity. The theta and beta power in each STN subregion, for each condition (congruent or incongruent) per hemisphere (ipsilateral or contralateral), were compared.

Results: Power in the gamma band confirmed accurate placement between dorsal (significantly higher) and ventral regions. A mixed effects model analysis showed beta power to be significantly larger in dorsal compared to ventral STN subregions, p<.01, and during conditions with action conflict versus those without conflict, p<.05. Moreover, beta power was higher in dorsal compared to ventral region during conflict conditions, p<.01. No effects of STN subregion, conflict condition, hemisphere, or their interaction were found for theta power.

Conclusion: Conflict-related increase in beta power is generally seen in tasks that require outright stopping. Our data suggest that this signal may also be important for temporarily pausing actions when conflicting action impulses are detected. Clinically, this could contribute to designing more focused DBS settings that optimize both clinical motor benefits and cognitive control.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/local-field-potential-differences-in-stn-subregion-during-performance-of-a-conflict-task-in-humans-with-parkinsons-disease/