Loss of certain mental functions due to the disintegration of integrative activity.Decrease in the level of personality or inferiority of intellectual functions of a person in comparison with the norm (congenital defect) or with a premorbid state (acquired defect after an illness). With a decrease in the level of personality, along with increased fatigue and irritable weakness, there is a general decrease in mental activity, a narrowing of the range of interests, and a gradual leveling of individual characterological properties.