Phineas Gage (1823-1860) was a railroad construction foreman who survived an accident where a tamping iron shot through his head, damaging the left frontal lobe of his brain. Gage reportedly suffered profound changes to his personality after the accident, and John Martin Harlow, one of the doctors who examined him wrote:
“His contractors, who regarded him as the most efficient and capable foreman in their employ previous to his injury, considered the change in his mind so marked that they could not give him his place again. He is fitful, irreverent, indulging at times in the grossest profanity (which was not previously his custom), manifesting but little deference for his fellows, impatient of restraint of advice when it conflicts with his desires, at times pertinaciously obstinate, yet capricious and vacillating, devising many plans of future operation, which are no sooner arranged than they are abandoned in turn for others appearing more feasible. In this regard, his mind was radically changed, so decidedly that his friends and acquaintances said he was “no longer Gage.””
Source:
Harlow, J. M. (1868) “Recovery from the passage of an iron bar through the head“, in Publications of the Massachusetts Medical Society 2:327–347