Apparently, some severe epilepsy patients, in the mid-twentieth century, their brain’s bridge (corpus callosum) got cut off, it was done because to avoid electrical storms from one part of the brain’s hemisphere to the other one.
Interestingly, because left hemisphere controls right part of the body and right hemisphere controls the other way around, they somehow have their own “self”. They are not in sync.
“… eerie behavior was displayed by patient WJ, a Second World War veteran. WJ’s hands were each controlled by a different hemisphere. Since the two hemispheres were not in touch with one another, it sometimes happened that his right hand would reach out to open a door, and then his left hand would intervene and try to slam the door shut.” A passage from Homo Deus by Yuval Noah Harari.
Yeah, so much for IN-DIVIDUAL.