DeCharms was still a graduate student at the University of California, San Francisco, in the 1990s when he started studying how the neural connections in the brain grow and change with experience, a phenomenon called neuro-plasticity. Neuroscientists knew that repeatedly exercising parts of the brain can elicit permanent changes in the complex neural circuitry responsible for, say, hearing or vision. DeCharms theorized that by consciously increasing or decreasing the neural activity in specific brain areas involved in disease, patients could control some of their symptoms and perhaps permanently change their brains for the better. DeCharms believes that patients with depression, for example, might be able to use fMRI feedback to learn to control the neurons that release the signaling molecule serotonin, and perhaps the cells serotonin acts on, as well. This would achieve the same goal as drugs like Prozac – increasing the amount of serotonin available in the brain – but might not produce side effects.
“If you practice a new form of dance, the first thing that happens is you learn to do the activity better. You engage the musculature, and it becomes stronger,” says deCharms. “Eventually, your physical body has been changed. It’s a long-lasting effect, even when you’re not consciously trying.” One key to strengthening the right dance muscles, of course, is feedback on your performance: dance studios always have mirrors on the walls. DeCharms hoped the same process would work in the brain, if he could find a way to measure brain activity rapidly and accurately enough for patients to learn to control it and to mimic desired patterns.
The idea of using feedback in the brain is not new. For 30 years, scientists have used electroencephalograms (EEG) – a technology that measures electrical activity coming from the brain – to train people to elicit or maintain a particular type of electrical pattern. Results from preliminary studies suggest that such training is somewhat effective for treating ADHD and substance abuse, though large, placebo-controlled studies have not yet been completed. But because EEG technology picks up electrical activity spanning multiple brain areas, its usefulness for specific feedback is limited. DeCharms wanted to target the anatomically tiny brain structures involved in disease, and in sensations like pain.
In contrast to EEG, fMRI measures the blood flow in precise areas of the brain, yielding much finer spatial resolution. It shows which areas are working hardest during a specific task, and it can also point out which parts of the brain are functioning abnormally in specific diseases. But for deCharms, it was the development of real-time fMRI that was the breakthrough. FMRI generates an enormous amount of data, which used to take days or weeks to analyze and interpret. But newer algorithms and greater computing power have collapsed that processing time down to milliseconds. That means scientists – and subjects – can watch brain activity as it happens.
For deCharms and his collaborators, this type of fMRI held a powerful appeal. They theorized that people with neurological or psychological disorders could perform mental exercises to try to modulate activity in specific neural systems that had gone awry and get immediate feedback on which strategies were most effective. Then they could use those strategies to feel better.