Deep brain stimulation (DBS) of the brain's electrical signals has achieved remarkable results for some neurological conditions. Its record for depression is more mixed, but this may be a consequence of a one-size-fits-all approach to treatment. When an individual received personalized stimulation based on their responses, long-lasting depression lifted within minutes; the team responsible are about to start a larger trial in the hope of replicating their success.
"The brain, like the heart, is an electrical organ, and there is a growing acceptance in the field that the faulty brain networks that cause depression – just like epilepsy or Parkinson's disease – could be shifted into a healthier state by targeted stimulation," Dr Katherine Scangos of the University of California, San Francisco said in a statement.
DBS involves the insertion of electrodes into the brain. It comes with the same costs and risks of surgery, but has been life-changing for some people with the conditions Dr Scangos mentions. It's been trialed for depression for 18 years, but encouraging early reports have not been replicated. Scangos thinks this is because treatments have not taken account of patients' individuality.
“Prior attempts to develop neuromodulation for depression have always applied stimulation in the same site in all patients, and on a regular schedule that fails to specifically target the pathological brain state,” Scangos continued. “We know depression affects different people in very different ways, but the idea of mapping out individualized sites for neuromodulation that match a patient's particular symptoms had not been well explored."
In Nature Medicine, Scangos and co-authors describe performing DBS on a patient whose major depressive disorder had failed to respond to psychotherapy, drugs, transcranial magnetic stimulation (TMS), or electroconvulsive shocks. The woman in the study has a family history of suicide, and her latest period of depression had lasted four years prior to the treatment, having suffered similar periods since childhood.
Ten electrodes were planted in the patient’s brain, and over a 10-day period, Scangos and colleagues stimulated different regions for up to 10 minutes at a time.
The response was dramatic. The woman described almost immediate distinct effects from stimulation of different brain regions. Stimulation of the orbitofrontal cortex at 1 Hertz produced a feeling “like reading a good book”, while the subgenus cingulate stimulation generated “neutral alertness...less cobwebs and cotton.” Some regions produced no response, and others made the patient feel worse. For example, she reported “doom and gloom...very scary” when her right amygdala was stimulated. For some regions, the response varied widely depending on the patient's mood at initiation – in one case calming when she was anxious, but worsening her mood when she was tired.
Once Scangos found the ideal combination the patient reported enjoying hobbies that had given her no pleasure for 5 years. "Every time they'd stimulate, I felt like, 'I'm my old self, I could go back to work, I could do the things I want to do with my life,'" she said. The benefits lasted for 6 weeks.
The patient was not told which parts of her brain were being stimulated, nor at which frequencies, yet her descriptions of the effects of particular regions being stimulated were too consistent to be a placebo effect. Moreover, her descriptions often matched with what we know about the region in question's function.
The same edition of the journal contains another paper on brain stimulation to reduce obsessive-compulsive behavior. The results, in this case, were less dramatic but involved external stimulation, rather than requiring surgery. Moreover, the study used a sample of 124 volunteers, who reported benefits lasted up to 3 months, rather than being conducted on a single individual.