Deep brain stimulation (DBS) is a treatment that surgically places electrodes in areas of the brain to disrupt various brain circuits. Physicians have used such neurostimulation devices to treat patients with Parkinson’s disease and epilepsy.
Doctors have suggested that DBS could treat some forms of depression, particularly for cases that have not responded to other conventional treatments. However, the areas of the brain that depression impacts can be different for patients. Making specific alterations to the devices to address the individual needs may make the devices appropriate for treating depression.
Researchers from the University of California, San Francisco (UCSF) have shared the case study of a woman named Sarah, who had a treatment-resistant major depressive disorder. Doctors successfully treated her using a neurostimulation device adapted to her specific needs. The researchers published their findings in the Journal Nature Medicine.
Dr. Katherine Scangos, assistant professor in psychiatry at the UCSF Weill Institute for Neurosciences and lead author of the paper, said this research showed that psychiatrists might be able to offer more personalized medicine in the future.
She said: “Evidence this kind of therapy can work provides hope to patients and is certainly something that is meaningful to me, in that we as psychiatrists will be able to help people with mental illness.”
“I think it suggests there could be a whole other type of treatments that are based on biomarkers that can deliver treatment in short time frames rather than antidepressants, which act on much longer time frames.”
Pinpointing a depression biomarker
The first objective for the researchers was to locate a “biomarker” for Sarah’s depression. This data would enable them to detect the abnormal brain activity causing the depression and target the electrical bursts to disrupt the correct brain area at the correct time.
Existing neurostimulation devices deliver constant electrical stimulation to the brain, so the researchers needed a method to detect and disrupt brain activity related to depression when it was occurring.
To meet this objective, the researchers conducted brain mapping by placing 10 electrodes across the left and right hemispheres of Sarah’s brain and recording neural activity across 10 days. Sarah reported the severity of her depressive symptoms using symptom rating scales during this time.
The researchers found that gamma frequency brain waves in the amygdala were most closely correlated with depressive symptoms. They used these as a biomarker for her depression.
Next, the researchers had to figure out how to disrupt these brain waves. They found that placing an electrode in the ventral capsule/ventral striatum at the base of the brain gave the most consistent improvement of symptoms when they applied electrical stimulation upon detecting abnormal brain activity in the amygdala.
Optimization of this process showed that applying very small amounts of electricity — 1 milliampere — for just 6 seconds at a time was sufficient to improve Sarah’s symptoms.
This new development gives future hope for adding another tool for doctors to use when a patient has depression that resists conventional treatments.