Frontal lobe disorder

Frontal lobe disinhibition is a neurological disorder where due to trauma or other underlying disease, the frontal lobe of the brain fails to function properly. The condition can be similar to alcohol intoxication, which also affects the functioning of the frontal lobe. It can manifest as lack of motivation, loss of the ability to plan, changes in social behavior, and changes in speech production.
In Mirror Mirror, the patient's frontal lobe is affected by infection, which manifests as the patient losing his own personality.
In The Social Contract, the patient's frontal lobe was affected by a tumor, which left him unable to suppress his thoughts so he blurted out everything he was thinking.
Frontal lobe disorder at Wikipedia
Frontal lobe disorder