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 a circuit-based treatment for severe, refractory obsessive-compulsive disorder (OCD).
• The precise mechanism by which DBS alleviates OCD symptoms is not fully understood, though it is hypothesized to involve modulation of cortico-striato-thalmo-cortical networks.

Purpose of the Study:

• To investigate the network effects of ALIC DBS in patients with severe OCD.
• To explore the relationship between functional brain activity changes and structural connectivity during DBS treatment.

Main Methods:

• Functional MRI (fMRI) with an On/Off cycling paradigm was used in five participants (3 responders, 2 non-responders) undergoing ALIC DBS for OCD.
• Diffusion-weighted imaging (DWI) and tractography were employed to assess structural connectivity between active DBS contacts and brain networks.

Main Results:

• Therapeutic ALIC DBS configurations suppressed BOLD activity in regions including the orbitofrontal cortex, dorsomedial prefrontal cortex, and subthalamic nuclei.
• Many suppressed regions were part of the default mode network (DMN).
• The stimulation field from therapeutic configurations showed significant structural connectivity to core DMN nodes.

Conclusions:

• ALIC DBS for OCD may exert therapeutic effects by suppressing the DMN.
• This suppression is hypothesized to occur through the interruption of communication along structural white matter tracts connected to the DBS electrodes.