Inability to remember things. Three functions are important in memory; the first is imprinting, the ability to repeat names or sets of numbers; the second is short-term memory; and important events are assigned to the third section, the long-term memory. Memory is seated in the deeper areas of the brain. Sudden temporary loss of memory is a characteristic symptom of concussion, caused by a blow to the head. The patient cannot remember what he was doing in the minutes or hours before the injury, the condition known as retrograde amnesia. The contents of the short-term memory seem to have been wiped out; it often also seems that nothing is retained either of what happened immediately after the injury. The patient is clearly conscious, but retains nothing of what is being said. This explains why someone with brain damage so often asks what happened. An epileptic seizure is also often followed by a short period of amnesia, as is a blackout from drinking too much alcohol. Persistent memory defects suggest damage to deeper areas of the brain. This occurs in dementia, severe concussion and severe subarachnoid haemorrhage. Imprinting difficulties make the patient forget what he has just said, the day of the week and where he is. The combination of this orientation disturbance combined with loss of memory is known as Korsakoff s syndrome. Because the imprinting difficulties also disable short-term memory, the condition is in a sense comparable with unconsciousness. Complete loss of memory, in which the patient is unaware of his own or others’ identities, is very rare, and in such cases a psychological element is also involved.