As an experiment, doctors treated severe cases of epilepsy by severing the corpus callosum, the bundle of nerves that connects the two hemispheres of the brain. This prevented the "thunderstorm" of electrical impulses from traveling around the brain and causing a seizure. This practice was very successful, however a new and more tragic malady would replace this dehabilitating disease.
As a result of severing the corpus callosum, the hemispheres of the brain could not communicate. Quite literally, the left hand did not know what the right was doing. Consequently, a separate, repressed personality would emerge, and fight for dominance over the body.
I witnessed film footage from the 70's of a young lady who had undergone this procedure. The doctor asked her a "yes-no" question to which the woman desperately wished to answer, "No". She stammered and stuttered, her frustration contorting her face. She looked quite pained as she attempted to force the word out, over and over.
The doctor then wrote on a small blackboard the words "YES" and "NO", and asked her to cover up the incorrect answer with her hand. As she reached out to cover the "YES", the other hand would lash out and grab or slap her hand away from the board. This went on briefly, since the doctor could see how hard this was for the young woman and ended the experiment.
Other cases report of their alien hands trying to take over steering of a car, or their legs trying to carry them away from department stores.
Sadly, the procedure was irreversible, leaving these victims to end their days in a constant battle with their inner duality. | 
