Scientists know that stimulating the deeper regions of your brain can treat Parkinson's and other conditions. But there's a problem: they usually need to open your skull to place implants, which is both time-consuming and risky. Researchers may have a better way, though: they've invented a deep brain stimulation technique that only requires electrodes on your scalp. The trick is to create two high-frequency electrical currents that don't do anything by themselves, but interact with each other deep inside your brain. If you want to target different parts of the brain, you just change the frequencies and placement of the electrodes.