Amnesia (from the Greek Ἀμνησία) is a condition of memory disturbance. The cause of amnesia may be organic or functional. Organic causes may include brain damage, due to trauma or disease, or the use of drugs (which are usually sedative). The cause of the functional is a psychological factor, such as ego defense mechanisms. Amnesia can also occur spontaneously, as occurs in transient global amnesia. This global type of amnesia is common from middle age until old age, especially in men, and usually lasts less than 24 hours.
amnesia consists of 2 types namely:
1. Retrograde amnesia: inability to bring back memories of the past more than ordinary forgotten events.
2. Anterograde amnesia: a new occurrence in the short-term memory is not transferred to long-term memory is permanent. Infected person will not be able to remember anything that happened after the emergence of this amnesia is just over a second though.
