The new study, published in the journal Nature Biomedical Engineering, is the culmination of years of work homing on the parts of the brain responsible for cognitive control. Impairments to cognitive control can be found in a number of mental health disorders, from depression to obsessive control disorder (OCD).
These cognitive control deficits manifest in inflexible thought processes. Alik Widge, from the University of Minnesota Medical School, says the inability to easily shift from one thought process to another is a key feature of many mental illnesses.
“An example might include a person with depression who just can't get out of a ‘stuck’ negative thought,” says Widge. “Because it is so central to mental illness, finding a way to improve it could be a powerful new way to treat those illnesses.”
A 2019 study from Widge and colleagues found electrically stimulating the ventral internal capsule/ventral striatum (VCVS) areas of the brain could enhance cognitive control. The earlier work not only demonstrated deep brain stimulation of VCVS regions improved cognitive control when participants were tasked with a cognitive control test, but it identified specific neural biomarkers that corresponded with clinical improvements.
From those earlier findings the researchers developed an algorithm that can detect, in real-time, when the brain is struggling with cognitive control tasks. When lapses in cognitive control are detected the system delivers short bursts of electrical stimulation to VCVS regions rapidly enhancing cognitive control performance.
“This system can read brain activity, ‘decode’ from that when a patient is having difficulty, and apply a small burst of electrical stimulation to the brain to boost them past that difficulty,” explains Widge. “The analogy I often use is an electric bike. When someone's pedaling but having difficulty, the bike senses it and augments it. We've made the equivalent of that for human mental function.”
The pilot study testing this experimental system recruited 12 subjects undergoing brain surgery for epilepsy. A few of the patients in the study did report the stimulation relieving symptoms of anxiety, but Widge is clear in noting this research can only focus on enhancing cognitive control and further work is needed before clinical trials can begin testing this kind of invasive brain implant on subjects with severe anxiety disorders.
“There's a lot still to do, and this is very clearly NOT a treatment for every case of depression/anxiety/OCD/anything else, but we think this is a pretty big step forward towards mechanism-driven DBS [deep-brain stimulation],” Widge asserts on Twitter. “This wasn't a clinical trial, but a few of the patients had significant anxiety, and boosting cognitive control allowed them to focus away from that anxious inner monologue.”
The new research is some of the first to demonstrate a brain implant can sense signs of a cognitive deficit in real-time and respond with targeted stimulation to restore normal neural activity. This kind of implant is known as a closed-loop system. It is similar to the way some cardiac pacemakers maintain optimal heart rates by stimulating the heart in response to sensing irregular activity.
These kinds of closed-loop brain stimulation implants have been used in the past to detect and treat epileptic seizures but the challenge researchers have faced in developing similar systems for mental illness is the lack of explicit neural biomarkers responsible for deeply multifaceted conditions such as depression or anxiety.
This new research indicates cognitive control deficits are common across many mental disorders, these deficits are easily measurable using cognitive control tests, and there are clear electrophysiologic signatures that correspond with these deficits. Widge and his team ambitiously speculate this kind of treatment could be useful for a variety of psychiatric diseases.
“The same framework could also be applied to other cognitive or emotional problems, for example, monitoring and enhancement of learning or emotion dysregulation,” the researchers conclude in the new study. “Although substantial technology gaps remain before these results can be directly applied in the clinic, and the evidence base needs to be built for cognition as a primary focus of treatment, our results could be the basis of a highly specific approach for intervention in human neuropsychiatric disease.”
The new study was published in the journal Nature Biomedical Engineering.
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