Therapeutic DBS for OCD Suppresses the Default Mode Network

Area of Science:

• Neuroscience
• Neurosurgery
• Psychiatry

Background:

• Deep brain stimulation (DBS) of the anterior limb of the internal capsule (ALIC) is an emerging treatment for severe, refractory obsessive-compulsive disorder (OCD).
• Therapeutic effects of DBS are hypothesized to involve modulation of cortico-striato-thalmo-cortical networks implicated in OCD.
• The precise mechanism of DBS in OCD remains unclear.

Purpose of the Study:

• To investigate the network effects of ALIC-DBS in OCD using functional MRI.
• To correlate functional network changes with structural connectivity using diffusion-weighted imaging (DWI).
• To elucidate the mechanism of therapeutic DBS in refractory OCD.

Main Methods:

• Functional MRI (fMRI) with a DBS On/Off cycling paradigm in five OCD participants (3 responders, 2 non-responders).
• Tractography using DWI to assess structural connectivity between active DBS contacts and brain networks.
• Analysis of BOLD activity changes in response to therapeutic vs. non-therapeutic DBS configurations.

Main Results:

• Therapeutic ALIC-DBS suppressed BOLD activity in the orbitofrontal cortex, dorsomedial prefrontal cortex, and subthalamic nuclei.
• Suppressed regions largely overlapped with the default mode network (DMN).
• Estimated stimulation fields showed significant structural connectivity to DMN nodes.

Conclusions:

• Therapeutic DBS for OCD effectively suppresses BOLD activity within distributed DMN regions.
• Proposed mechanism involves interrupting communication via white matter tracts surrounding DBS contacts.
• Findings provide insights into the network-level effects of ALIC-DBS for OCD treatment.