Objective: To evaluate the impact of subthalamic deep brain stimulation on language network connectivity in participants with Parkinson’s disease (PwPD) by comparing resting state functional MRI while DBS is turned ON versus OFF.

Background: One of the most frequently reported unwanted side effects of STN-DBS includes disruptions to verbal fluency. Verbal fluency requires the engagement of motor and language networks. To date most studies investigating the neural basis of verbal fluency changes following STN-DBS have used normative data, however, this approach is limited in its sensitivity to patient specific neural responses to stimulation. Furthermore, studies have not established the extent to which language networks are impacted. Thus, this prospective study evaluates how STN-DBS modulates language network connectivity.

Method: We prospectively collected neuroimaging and verbal fluency data from PwPD and STN-DBS implants approximately 1 year following surgery. Verbal fluency data from four participants was ON and OFF DBS. Resting state fMRI data (24-minuites ON DBS and 24-minuites OFF DBS) was collected to evaluate changes in functional connectivity induced by STN-DBS. DBS settings were set to an MRI-safe bipolar mode and adjusted to match the clinical VTA. Changes in functional connectivity in the ON versus OFF conditions were assessed by using a seed to whole brain approach in which nodes of the language network were used as seeds in CONN toolbox.

Results: Our results demonstrated that there was an increase in functional connectivity between the left posterior superior temporal gyrus seed and the supramarginal gyrus and angular gyrus (voxel threshold p<0.005, cluster p<0.05) in the OFF condition compared to the ON condition. In addition, there was an increase in connectivity between the right posterior superior temporal gyrus seed and the supplementary motor area (voxel threshold p<0.005, cluster p<0.05) in the OFF versus ON condition.

Conclusion: These preliminary results provide evidence STN-DBS induces modulation of language network nodes and their interaction with the motor network. This indicates that neural processes underlying networks beyond the motor network could contribute to verbal fluency changes. Larger samples using this approach will examine the relationship between verbal fluency changes and modulation of language networks.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/subthalamic-nucleus-deep-brain-stimulation-impact-on-language-network-connectivity/