Some of them suffered from incurable epilepsy, intractable physical pain, Parkinson's disease, and other medical conditions, but most came out of the dimly lit back wards of the state mental hospitals. We'd interview a patient about pleasant subjects and see the pleasure system firing. If we had a patient who flew into a rage attack, as many psychotics did, we'd find the 'punishment' system firing. Whenever a mental patient flew into a violent rage or turned into a catatonic zombie, the EEG was almost certain to display the telltale sawtooth pattern. It's a defect in the pleasure response.
Schizophrenics have a predominance of painful emotions.
And so Heath tried to cure mental illness with direct electrical stimulation of the pleasure neurons. As it turned out, it took more than a few pulses of current to exorcise madness. Heath had to devise safer electrodes that could be left in the brain for years so that a patient could be restimulated at intervals. The pacemaker is an array of tiny battery-powered electrodes that delivers 5 minutes of stimulation every 10 minutes to the cerebellum, at the very back of the brain. Its power source, a battery pack about the size of a deck of playing cards, could fit neatly in the patient's pocket.