Deep-brain stimulation is used in a number of therapies, for diseases such as Parkinson’s, major depression, OCD, dystonia. It is also used to lessen chronic pain and to help regulate Essential tremors.
This involves drilling a 1.4cm hole in the head, then inserting electrodes into the brain into the affected part.
Obviously, there are risks involved in this.
A team at MIT has come up with a method to provide stimulation at any desired part of the brain using electrodes that are placed on the scalp instead of embedded within the brain. No surgery required.
How it works is that the electrodes, placed on either side of the head, give out waves of electricity. The waves interfere with each other like two waves meeting in a pond, cancelling each other out except for in specific points where the waves are intensified instead.
An advantage to this method is that the intersection points can be “steered” by adjusting the waves.
My opinion: this method should make a lot of surgeries unnecessary, and will make the therapies for those disease so simple that it might eventually be possible to simple buy an off-the-shelf electrode cap and run some open source software to fix your issues.