Inside the Strange New World of DIY Brain Stimulation

Don't do this. Think of the botched execution of Eduard Delacroix in the Green Mile. I'm sure your doctor has no intention of helping your cognition this way.  You're just a stroke-addled patient who should have prevented your stroke in the first place.
http://www.wired.com/2014/05/diy-brain-stimulation/
But it is a wonderful picture from there.
Ward Sutton