These two types are not mutually exclusive both can occur simultaneously. People with anterograde amnesia cannot remember things for long periods of time. Anterograde amnesia is the inability to transfer new information from the short-term store into the long-term store. In some cases the memory loss can extend back decades, while in others the person may lose only a few months of memory. Retrograde amnesia is the inability to retrieve information that was acquired before a particular date, usually the date of an accident or operation. There are two main types of amnesia: retrograde amnesia and anterograde amnesia. The memory can be either wholly or partially lost due to the extent of damage that was caused. Amnesia is a deficit in memory caused by brain damage or disease, but it can also be caused temporarily by the use of various sedatives and hypnotic drugs.