Obsessive-Compulsive Disorder (OCD) is a common mental health condition causing neurotic thoughts and compulsive behaviours. OCD symptoms include persistent obsessive thoughts and unpleasant compulsions like irrational behaviour that makes no logical sense.
To improve treatment for OCD, researchers recorded electrical signals in the human brain associated with ebbs and flows in OCD symptoms over an extended period in their homes as they went about daily living.
The research could make an emerging therapy called deep brain stimulation responsive to everyday changes in OCD symptoms.
OCD symptoms affect 2% of the population
OCD affects approximately 2% of the population and is often debilitating. According to research, 20-40% of cases do not respond to traditional drug or behavioural treatments.
Deep brain stimulation (DBS), a technique involving small electrodes precisely placed in the brain that deliver mild electrical pulses, effectively treats over half of the patients where other therapies have failed.
Although DBS has its limitations, including the inability to adjust to momentary changes in OCD symptoms impacted by the physical and social environment, an adaptive DBS can adjust the intensity of stimulation in response to real-time signals recorded in the brain could be more effective and reduce unwanted side effects.
“OCD is a disorder in which symptom severity is highly variable over time and can be elicited by triggers in the environment,” said David Borton, an associate professor of biomedical engineering at Brown University, a biomedical engineer at the U.S. Department of Veterans Affairs Center for Neurorestoration and Neurotechnology and a senior author of the new research. “A DBS system that can adjust stimulation intensity in response to symptoms may provide more relief and fewer side effects for patients. But to enable that technology, we must first identify the biomarkers in the brain associated with OCD symptoms, and that is what we are working to do in this study.”
The research, led by Nicole Provenza, a recent Brown biomedical engineering PhD graduate from Borton’s laboratory, was a collaboration between Borton’s research group, affiliated with Brown’s Carney Institute for Brain Science and School of Engineering; Dr Wayne Goodman’s and Dr Sameer Sheth’s research groups at Baylor College of Medicine; and Jeff Cohn from the University of Pittsburgh’s Department of Psychology and Intelligent Systems Program and Carnegie Mellon University.
Deep brain stimulation for OCD
The study recruited five participants with severe OCD who were eligible for DBS treatment. Sheth, the lead neurosurgeon, implanted each participant with an investigational DBS device from Medtronic capable of delivering stimulation and recording native electrical brain signals. The team gathered brain-signal data from participants in clinical settings and at home as they completed daily activities.
The team also collected a suite of behavioural biomarkers. In a clinical setting, these included facial expressions and body movement. Through using computer vision and machine learning, the researchers discovered that behavioural features were associated with changes in internal brain states. At home, participants self-reported OCD symptom intensity along with biometric data – heart rate and general activity – recorded by a smartwatch and smartphone application by Rune Labs. All behavioural measures were time-synched to the brain-sensing data, enabling the researchers to look for correlations between the two.
“This is the first time brain signals from participants with the neuropsychiatric illness have been recorded chronically at home alongside relevant behavioural measures,” Provenza said. “Using these brain signals, we may be able to differentiate between when someone is experiencing OCD symptoms, and when they are not, and this technique made it possible to record this diversity of behaviour and brain activity.”
Provenza’s analysis of the data showed that the technique did pick out brain-signal patterns potentially linked to OCD symptom fluctuation. Whilst, more work needs to be done across a larger cohort, the initial study showed that this technique is a promising way to confirm candidate biomarkers of OCD.
“We were able to collect a far richer dataset than has been collected before, and we found some tantalising trends that we’d like to explore in a larger cohort of patients,” Borton said. “Now we know that we have the toolset to nail down control signals that could be used to adjust stimulation level according to people’s symptoms.”
An adaptive deep brain stimulation system
Once those biomarkers are identified, they could be used in an adaptive DBS system. Adaptive DBS systems stimulate and record brain activity and behaviour continuously at home. When the system detects signals associated with increases in OCD symptom severity, it could increase the stimulation to potentially provide additional relief. Alternatively, stimulation can reduce once symptoms lessen.
“In addition to advancing DBS therapy for cases of severe and treatment-resistant OCD, this study has the potential for improving our understanding of the underlying neurocircuitry of the disorder,” Goodman said. “This deepened understanding may allow us to identify new anatomic targets for treatment that may be amenable to novel interventions that are less invasive than DBS.”
The research is ongoing as OCD is a complex disorder that manifests itself in highly variable ways across patients. The researchers hope to expand the number of participants to capture more variability. They are seeking to identify a fuller set of OCD biomarkers that could guide adaptive DBS systems. Once those biomarkers are in place, the team hopes to work with device-makers to implement their DBS devices.
“Our goal is to understand what those brain recordings are telling us and to train the device to recognise certain patterns associated with specific symptoms,” Sheth said. “The better we understand the neural signatures of health and disease, the greater our chances of using DBS to successfully treat challenging brain disorders like OCD.”
