Short term memory holds a small amount of information for just a short period of time. Stanford University states that the capacity of short term memory is seven items, plus or minus two. If a patient has short term memory loss, then she is unable to retain the new information for longer than a few minutes. Short term memory loss can be caused by damage to the brain, such as from an illness or an injury.
Can't Recall Recent Events
Stanford University notes that unaffected short term memory has a rapid loss of information, meaning that the data is held for only a few seconds before it is passed on to be consolidated into a long term memory. For a patient with short term memory loss, that mechanism is defunct, leading to all new information being discarded. The Foundation for Health in Aging (FHA) notes, however, that stored memories, or long term memories, are not affected by short term memory loss.
Confusion from Memory Loss
The FHA states that the memory loss can range from mild to severe; in mild cases, the patient can function without much difficulty. However, a patient with severe short term memory loss can have problems taking care of himself and can become incredibly confused from the memory loss. Because the patient is unable to retain new information, he becomes "stuck" in his existing memories, and becomes confused when told things are different, such as it is a different year or that someone has died.
Information Lost with Attention Change
A diversion in attention can result in a patient with short term memory loss to lose her short term memories. Stanford University notes that short term memory is characterized by a limited capacity and a rapid loss of information, so it needs selective attention to store information. In a normal patient, a change in attention would not cause a loss of information: much of that data would have moved on to consolidation. But since a short term memory loss patient does not have that mechanism, distracting her would result in her forgetting everything temporarily stored in her short term memory. For example, if the patient was reading a page and her attention was drawn to someone entering the room, she would not remember what she was reading; in severe memory loss cases, she might not even remember that she was reading.
