Depending on what part or parts of a person's brain are injured, the individual may experience significant behavioral and emotional changes.
The frontal lobe, for example, helps govern personality and impulsivity. If damaged, there might be no "braking mechanism" for self-control. A person may find he cannot control his anger or aggression. He may also make inappropriate comments to friends or strangers not realizing they are off color. Or the opposite might happen — someone's personality may become muted or seemingly emotionless. This is called "flat affect."