Electrical brain stimulation in people with pre-existing brain implants has allowed them to think more flexibly and clear anxious thoughts, suggesting it has the potential to treat conditions like depression.
at the University of Minnesota and his colleagues found that applying an electric current within the centre of the brain boosted people鈥檚 ability to rapidly adapt to changing goals, known as cognitive control, and in some cases improved their feelings of well-being too.
The inability to disengage from habitual ways of thinking is commonly seen in people with mood disorders, such as depression and obsessive compulsive disorder. In these conditions, people are often unable to extricate themselves from thought processes triggered by habits or distress.
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Widge recruited 21 people who already had electrodes placed in their brain as a treatment for epilepsy. They did not have depression, but some had mood disorders associated with epilepsy. He and his team used these electrodes to provide small bursts of stimulation to the brain while participants performed a cognitive control task, in which they were shown a trio of numbers between one and three on a screen. Two of the numbers were always the same, and their task was to identify the odd number out and press the corresponding key on a keypad.
In some tasks, the position of the unique number matched its physical position on the keypad, in other tasks it didn鈥檛. The task forces participants to use cognitive control to overcome the difference between where the number is on the screen and the keypad.
When their brains were stimulated, participants were around 5 per cent faster at answering correctly. It might not seem like much, says Widge, but you don鈥檛 need a lot of change in flexible thinking to help people make small tweaks in their life that can then accumulate over time and help change behaviours.
Although the participants couldn鈥檛 tell when the stimulation was switched on and off, in trials where it was on some of them reported that their thoughts were more focused and their background anxiety was easier to ignore, suggesting the stimulation may have had an influence.
Because the researchers were working with people who already had electrodes implanted, they couldn鈥檛 stimulate the same area of the brain in each person, though they found the dorsal part of the internal capsule, an internal highway that connects to multiple structures in the front of the brain involved in complex decision-making, provided the best results.
In further experiments, the team only stimulated the brain when participants鈥� accuracy fell below a specific threshold 鈥� this 鈥渃losed loop鈥� technique doubled the effect of the stimulation, making participants 10 per cent faster, says Widge. The researchers later showed that they could identify falls in accuracy based on patterns of brain activity alone.
As a result, it may be possible to record and stimulate the brain only when necessary to provide relief from specific brain activity that underlies conditions like depression. Because the implants are invasive, this would probably be only used for treatment-resistant conditions, but doctors have already started using this kind of treatment.
Deep brain stimulation for psychiatric conditions has had varied results, says at King鈥檚 College Hospital. Part of the reason may be because the method of delivery isn鈥檛 specific enough. This kind of personalised, closed loop delivery, may therefore be key to effective treatment, he says. 鈥淢uch research still needs to be done, but at least we now have a starting point.鈥�
at Imperial College London says the new study represents exciting work, which demonstrates the utility of sophisticated and personalised brain stimulation tools. He hopes it will motivate exploration of similar approaches with less invasive stimulation.
There have been concerns that brain stimulation could alter people鈥檚 authentic selves, but in Widge鈥檚 opinion, this isn鈥檛 a realistic fear. 鈥淲e have consistently found that patients do not perceive stimulation as changing who they are, they perceive it as allowing their true self to finally come out from behind the cloud of their disease. They鈥檒l say, 鈥業鈥檓 me, just me without depression鈥�.鈥�
Nature Biomedical Engineering
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