Researchers identify brain circuits responsible for triggering OCD symptoms

Most of the time, the origin of obsessive-compulsive disorder (OCD) is unknown, but in some rare cases, it starts after a brain injury, such as a stroke or a tumor. Researchers at the Champalimaud Foundation, in Lisbon, have identified brain circuits underlying these “lesional” OCD cases. They also provide data to suggest that acting on these circuits by brain stimulation techniques could help improve the treatment of “non-lesional” OCD, which is much more common.

Obsessive-compulsive disorder (OCD) can be an extremely incapacitating neuropsychiatric condition. The symptoms of people who suffer from OCD can entail washing their hands or showering over and over again, repeatedly checking whether they switched off the gas in the kitchen or locked their street door. In the most extreme cases, this takes up so much of their time and energy that they become unable to leave their house, to work, to develop meaningful relationships and to interact with other people.

Repetitive TMS is a non-invasive, painless technique, which has proven its efficacy for the treatment of not only OCD, but also other neuropsychiatric disorders such as resistant depression. In rTMS treatments, an electromagnetic coil is applied to a precise location on the head of the patient, delivering electromagnetic pulses that are capable of modifying the neuronal activity of a target brain area. The rationale here is that if that brain area's neural activity is causing the condition, changing it will alleviate the symptoms.

However, when treating OCD with rTMS, it is uncertain whether the stimulated target brain area is causally linked to the OCD symptoms the patients experience. Standard neuroimaging – with functional MRI (magnetic resonance imaging) – of OCD patients' brains shows associations between the presence of symptoms and abnormal patterns of activity. However, this approach cannot distinguish cause from consequence: does the symptom result from the altered activity, or does the changed brain activity result from the symptom or the responses to the symptom?

Using the human connectome (that is, the average resting-state functional brain connectivity extracted from fMRI of 1000 healthy individuals), each lesion's functional "neural map" was computed and the maps of OCD lesions were compared against control lesions, to extract OCD-specific circuitry.

He adds: "As to the basal ganglia, we also have evidence showing a relationship to compulsions. Once you engage in a certain act, it's very difficult to stop because this circuit is reinforced to do this act again, and again, and again, surely also because of connections to the OFC."

The results could have implications for improving the treatment of OCD with rTMS. The researchers are currently performing a clinical trial, funded by the Brain and Behaviour Research Foundation (BBRF, a prominent global nonprofit organization and one of the largest non-governmental funders of mental health and neuropsychiatric research. The trial aims at comparing the efficacy on the improvement of OCD clinical symptoms of stimulating the standard rTMS target regions versus that of stimulating the newly-identified lesional OCD network.

"That means that ultimately, and that's the next step of the project, we may use our lesional OCD network as a tool to guide neuromodulation treatment, instead of relying on average places", says Albino J. Oliveira-Maia, senior author of the study. "This could also allow for more individualized targeting, picking the cortical spot that, in each individual patient, best matches the OCD circuit we describe here."

Source:

Champalimaud Centre for the Unknown

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