Phineus Gage, a man working in railroad construction was filling a hole with gunpowder and when sparks caused the powder to explode. The blast projected a bar a meter in length and 3.2 centimeters in diameter through his skull. It entered his left cheek, destroyed his eye, through the left front of his brain and out the top of his head.

He survived and woke up a few minutes later able to walk and talk. After some healing complications, it was apparent that the injury altered his personality. Before the injury Phineas was gentle and easy going but after he became rude, irrational, irritable, and had abandoned his plans for the future. His memory and cognition were not affected. After four years his old personality started to come through again, which shows that rehabilitation may be possible after traumatic injury. 

Phineas Gage's case is possibly the first case to suggest that different areas of the brain play a role in determining personality and that certain parts, when affected, can lead to specific mental changes (Teles Filho, 2020).