Novel Approach to Mental Illness? Brain Implant Detects, Improves Deficits in Cognitive Control

Deficits in cognitive control—the ability to flexibly alter strategies or response styles—are common across psychiatric disorders. This is especially true of patients with mood and anxiety disorders, who are often unable to disengage from habitual, distress-driven thoughts and behavior.

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Massachusetts General Hospital researchers previously showed, in Nature Communications, that deep brain stimulation (DBS) of a brain region called the internal capsule improved human cognitive control and the functioning of the prefrontal cortex. In fact, they identified specific neural biomarkers that corresponded with clinical improvement.

Sydney S. Cash, MD, PhD, co-director of the Center for Neurotechnology and Neurorecovery in the Department of Neurology, Darin D. Dougherty, MD, director of the Division of Neurotherapeutics, and colleagues have built on those findings. In Nature Biomedical Engineering they provide proof-of-concept that it might be possible to use DBS along with artificial intelligence to improve cognitive control as a treatment for psychiatric illnesses.

Methods

Using the biomarkers they identified in their earlier work, the researchers created a system for closed-loop direct stimulation of the internal capsule. A computer algorithm decodes neural activity to detect deficits in a person's cognitive control in real time, and if necessary the controller delivers precisely targeted DBS to restore normal neural activity.

The team piloted the controller in 12 patients with longstanding, pharmaco-resistant epilepsy who were undergoing invasive multi-electrode monitoring for seizure localization. During the surgery, the patients performed a cognitive control task, the Multi-Source Interference Task (MSIT). Before and during their hospital stay they completed self-report scales related to emotions and cognition.

Results

As in the earlier study population, brief internal capsule stimulation rapidly enhanced cognitive control. The improvement was evident in performance on the MSIT as well as in recordings of neural activity.

Participants were not able to directly identify when stimulation was on or off, but they perceived when their performance on the MSIT was better. What's more, two participants who had previously scored low on self-regulation of emotion noted relief from their usual anxiety. No participant reported negative emotional effects.

Considerations for Future Research

These findings suggest cognitive control might be useful as a psychiatric treatment target regardless of the patient's diagnostic label. However, substantial hurdles must be overcome before the controller can be adopted for practical clinical use:

• There are probably multiple points in the frontostriatal network that would be beneficial to stimulate, and broader studies, including in animals, are needed to clarify which targets are most useful in which situations
• Although key aspects of cognitive control are readily measurable using tasks such as the MSIT, there are no well-established diagnostic and monitoring scales for cognitive control
• Careful consultation with bioethicists is needed before the controller is used outside a restricted research setting—there are societal concerns about altering personalities or authentic selves through cognitive enhancement and whether it should be used to improve performance in healthy people

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