A new study shows that non-invasive brain stimulation in the form of mild electrical currents might be the answer. cnn's chief medical couldn't dr. sanjay gupta is here to tell us more about this research. so, sanjay, one, where do i sign up? and, two, how exactly does this work? >> well, this was mostly for people over the age of 65, kaitlan. so you have some time, hopefully, before you need something like this. it is kind of remarkable research. brain surgery, that's my area. and the idea that you could start to non-invasively stimulate the brain, it is a relatively new idea. why? because th...