A patient is 60-year-old, retired, worked as deputy director of a research institute. Behavioural changes appeared 2 years ago after the death of her husband: she stopped looking after herself and leaving the house; then she stopped to clean the apartment and cook. Mental status: temporal disorientation. The patient does not understand many of the questions, is confused; does not know how to cook soup or fasten a button. Her speech is characterized by stumbling and logoclonia. She does not recognize doctors, fellow patients. She cries a lot but can not explain thereason for tears. What is the mechanism of thispathology?