Memory impairment refers to a state in which an individual is unable to remember or recall information or skills, either permanently or temporarily, possibly due to pathophysiological or situational causes. Memory includes recognition, retention, and reproduction, and is closely related to neuropsychological functioning. According to neurophysiological and biochemical studies memory is divided into transient memory (within minutes and seconds) short term memory (days) and long term memory (months and years). Memory and forgetting are concomitant, and forgetting has a temporal pattern and selectivity. Newly memorized material is forgotten fastest, gradually progressing to distant forgetting, and things that once attracted high attention are more difficult to forget. The classification is as follows: 1, memory enhancement (hypermnesia) Clinically common in patients with hypomania, the association of accelerated “unforgettable” and can recall details of past events that normally can not be recalled depressive disorder patients also have a similar situation is mainly manifested in the memory of the past small mistakes vividly after the remission of the above phenomenon disappeared. 2, memory weakness (hypomnesia) memory process of the overall decline in function is most common in organic brain mental disorders such as dementia patients can also be seen in normal elderly people. 3, amnesia (amnesia) to an event or an experience can not be recalled is called a recall gap can be retained to re-recognition function is divided into prograde amnesia retrograde amnesia progressive amnesia psychogenic amnesia the first two categories are mostly seen in brain injury progressive amnesia is mainly seen in dementia psychogenic amnesia has the characteristic of selective amnesia, that is, what is forgotten is selectively limited to painful experiences or things that may cause psychological pain mostly in major It occurs after psychological stress and is common in dissociative disorder acute stress disorder (acutestressdisorder), etc. 4.misconstruction (paramnesia) A kind of memory error when the patient recalls his own personal experience of the event of the place, especially the time of memory errors or confusion, such as the time of the event occurred in this period of time as in another time. 5. confabulation is also a kind of memory error in which the patient forgets a personal experience and fills in and replaces it with a completely fictitious story, and then firmly believes that some patients talk about most of the content as remnants of past memories, which are richly and vividly linked together under the induction of the questioner and appear to be absurd, but are immediately forgotten clinically, it is called false talk disorder, which is mostly seen in organic brain disorders such as dementia Patients with dementia and chronic alcoholic psychosis. 6. kryptomnsia, also known as distorted memory, is a condition in which the patient recalls other people’s experiences and what he or she has seen and heard as his or her own or recalls his or her real experiences as what he or she has seen and heard of other people’s experiences.