Can Deep Brain Stimulation Target a Common Brain Network in OCD?

What you need to know

• Deep brain stimulation (DBS) can effectively treat severe obsessive-compulsive disorder (OCD), but different brain targets are used.
• This study examined if DBS to different targets affects a common brain network in OCD patients.
• The researchers found evidence for both shared and target-specific brain networks associated with symptom improvement.
• A set of brain regions including the anterior cingulate cortex, insula, and precuneus were linked to improvement regardless of DBS target.
• The findings may help refine DBS targeting and identify new potential treatment targets for OCD.

Background on OCD and deep brain stimulation

Obsessive-compulsive disorder (OCD) is a mental health condition characterized by recurring, intrusive thoughts (obsessions) and repetitive behaviors (compulsions). For about 10% of OCD patients, conventional treatments like medication and psychotherapy are not effective. In these severe cases, deep brain stimulation (DBS) may be used as an alternative treatment option.

DBS involves surgically implanting electrodes in specific areas of the brain and delivering electrical pulses to modulate abnormal brain activity. Several different brain targets have been used for DBS in OCD, including regions called the anterior limb of the internal capsule (ALIC) and the subthalamic nucleus (STN). However, it’s unclear if stimulating these different targets affects the same or different brain networks.

Study examines brain networks affected by DBS

To investigate this question, researchers analyzed data from 50 OCD patients who received DBS to either the ALIC or STN regions. The patients came from four different medical centers in Europe. The study aimed to determine if there were common brain networks associated with symptom improvement across the different DBS targets.

The researchers used advanced neuroimaging and analysis techniques to examine how the stimulated brain areas were functionally connected to other regions throughout the brain. They then looked at how these connectivity patterns related to patients’ clinical outcomes, measured by changes in OCD symptom severity after DBS treatment.

Evidence for both shared and target-specific networks

The analysis revealed evidence for both commonalities and differences in the brain networks associated with symptom improvement between the ALIC and STN targets:

• A set of brain regions showed similar patterns across both targets. Connectivity between the stimulation sites and areas like the anterior cingulate cortex, insula, and precuneus was associated with better clinical outcomes regardless of DBS target.

• However, there were also some differences. For example, connectivity to the orbitofrontal cortex was linked to improvement for STN stimulation but not ALIC stimulation.

• When the researchers focused on just the common regions across targets, this “agreement map” was actually better at predicting symptom improvement than looking at the full brain connectivity patterns.

These findings suggest there may be a core brain network involved in OCD symptoms that can be modulated by DBS to different targets. At the same time, stimulating different regions may also have some distinct effects.

Implications for understanding and treating OCD

This study provides new insights into the brain circuits involved in OCD and how DBS may help alleviate symptoms. Some key implications include:

1. Refining DBS targeting: Understanding the optimal connectivity patterns associated with improvement could help surgeons more precisely place DBS electrodes in individual patients.

2. Identifying new treatment targets: By mapping out the key brain regions and connections involved, this work may reveal new potential targets for both invasive and non-invasive brain stimulation therapies.

3. Personalizing treatment: The differences seen between targets suggest DBS could potentially be tailored to target specific symptoms or subtypes of OCD.

4. Integrating invasive and non-invasive therapies: The brain regions identified overlap with targets used for non-invasive treatments like transcranial magnetic stimulation (TMS), suggesting possibilities for combining approaches.

The core OCD network

The brain regions that showed consistent associations with symptom improvement provide clues about the neural circuits underlying OCD. Some key areas identified include:

• Anterior cingulate cortex (ACC): This region is involved in error detection, conflict monitoring, and emotional regulation. Hyperactivity of the ACC has been linked to excessive worrying and doubt in OCD.

• Insula: This area plays a role in interoception (sensing internal bodily states) and processing emotions. Altered insula activity may contribute to heightened anxiety and awareness of bodily sensations in OCD.

• Precuneus: This region is part of the brain’s default mode network and is involved in self-reflection and mental imagery. It may play a role in the repetitive thoughts characteristic of OCD.

• Striatum: This subcortical region is involved in habit formation and reward processing. Abnormal activity in cortico-striatal circuits is thought to contribute to compulsive behaviors in OCD.

The involvement of these diverse regions highlights how OCD affects multiple cognitive and emotional processes. DBS may work by helping to normalize activity across this distributed network.

Limitations and future directions

While this study provides valuable new insights, there are some limitations to note:

• The analysis was based on brain connectivity in healthy individuals rather than OCD patients. Future work using patient-specific brain imaging could provide more precise mapping of relevant circuits.

• The study focused on overall symptom improvement and did not look at effects on specific OCD subtypes or symptom dimensions. More detailed clinical data could help clarify if different network effects relate to particular aspects of OCD.

• This was a retrospective analysis of existing patient data. Prospective studies will be needed to validate the predictive value of the identified brain networks.

Future research directions may include:

• Testing if the identified networks can predict DBS outcomes in new patients
• Examining how DBS changes brain connectivity over time
• Investigating if non-invasive brain stimulation (e.g. TMS) targeting the same networks can benefit OCD patients
• Exploring how medications or psychotherapy may interact with these circuits

Conclusions

• DBS for OCD appears to modulate a core brain network involved in symptoms, regardless of the specific stimulation target used.
• Both shared and target-specific connectivity patterns were associated with symptom improvement.
• Key regions like the anterior cingulate cortex, insula, and precuneus may be central to the therapeutic effects of DBS in OCD.
• These findings could help refine and personalize brain stimulation treatments for OCD in the future.
• More research is needed to validate these results and translate them into clinical applications.

This study represents an important step toward a more unified understanding of how DBS affects brain circuits in OCD. By bridging across different stimulation targets, it provides a framework for optimizing and personalizing this promising therapy for severe, treatment-resistant OCD.