maber's most dramatic success stories. >> pretty good, huh? the time, but this gives me the capacity that if i can, if there is joy in my life, i have the capacity to feel it. >> reporter: but what exactly is going on? what is dbs doing to the brain circuits. what to we know and don't we know about why this works? >> to be honest, we don't know why it works. >> reporter: if area 25 is so important, why isn't everyone getting it done? >> maybe we are doing something wrong. maybe they're not the right patient. that means we've got to understand the biology better. >> reporter: in addition to depression, started looking for obsessive-compulsive disorder, epilepsy, tur tourette's syndrome and alzheimer's. in the meantime, edie geiten is thankful for her new life. >> oh! >> reporter: with the battery pack delivering 1/1000th of the power that a flashlight uses. do you feel electricity or anything? >> i don't feel anything in my head at all. did you go off medication when you were pregnant? >> reporter: she's active with the mental health advocacy a