The short answer is deep brain stimulation (DBS), a targeted form of electrotherapy used to treat brain disorders like Parkinson's disease and OCD. The long answer, i.e. why DBS is sometimes so remarkably effective, remains poorly understood – but researchers this week took a big step on their path to understanding the technique.
Above: Andrew Johnson flips the switch on his DBS implant, with dramatic results. DBS is not a miracle cure – it's an FDA-approved surgical procedure that's been cleared for the treatment of Parkinson's disease for over a decade. Johnson has responded to the treatment extraordinarily well. For the full video, and more info, see here.
Here's Motherboard's William Herkewitz, on what he calls (a little breathlessly for my taste, but I'll get to that in a moment) "the first unifying theory" of brain stimulation's effectiveness:
"It really astounds me every time I implant a patient with a deep brain stimulator," says Michael Fox, a neuroscientist at Harvard Medical School. "You can see this enormous therapeutic benefit, but as a scientist you're absolutely struck by how little we know about what it actually does to the brain."
Although it's been used in medicine for over 15 years, modern neuroscience still can't explain what zapping the brain with electricity actually does, and why doing it can help fight disease. But today, a team of neuroscientists lead by Fox has put forth the first unifying theory. In a paper published in this week's edition of the science journal Proceedings of the National Academy of Sciences, Fox has provided proof that all brain stimulation techniques work by hacking into discrete circuits of brain cells—and that for specific diseases, like depression, all stimulation treatments (that work) tap into the very same circuit.
Fox's research team came to this conclusion by overlaying a newly developed map of the human brain's connectome—the rough circuit diagram of how groups of neurons are connected with one another—onto a massive trove of clinical data detailing where effective brain situation treatments were focused for 14 different diseases. All the treatments—which were for diseases as varied as Parkinson's, Tourette's, epilepsy, and anorexia—fit into the circuit-theory. "This shows that if you want to understand the mechanics of brain stimulation, you have to think about a network effect," Fox says.
What Fox and his colleagues have done is combine a popular neuroscientific hypothesis – that brain disorders are, fundamentally, disorders of neurological circuitry – with big data from initiatives like the Human Connectome Project. The result is a framework which, if it is adopted by the research community and proven to be empirically useful, could help bridge the considerable gap that divides brain stimulation research and its clinical applications. But it's a little early, I think, to call it a "unifying theory"
Even if it is used, in this instance, to describe brain stimulation specifically rather than the field of neuroscience as a whole, "unified theory" is something of a loaded term in the fields of neuroscience and psychology (see here and here), both of which stand to benefit from Fox's team's framework. For now, it's safe to call Fox's team's framework a significant achievement – but, as Fox himself points out in his interview with Motherboard, how that framework will help advance science's understanding remains to be seen.