Short-term memory loss is the inability to remember new information, compared to long-term memory loss, where recalling past information becomes difficult. Short-term memory loss stems from damage to the medial temporal lobe, which is located towards the center of the brain, around the ear; the hippocampus is found in the medial temporal lobe, and when damaged, it cannot consolidate short-term memories into long-term memories. The type of short-term memory loss depends on the cause of the damage.
Surgical Damage
Short-term memory loss can occur when the medial temporal lobe is damaged during surgery. A famous case of surgical memory loss involves a patient known only as "H.M.," who underwent surgery for frequent seizures at Hartford Hospital in 1953. Dr. Suzanne Corkin, who studied and worked with H.M. until his death in 2008, notes in her article, "Lasting Consequences of Bilateral Medial Temporal Lobectomy: Clinical Course and Experimental Findings in H.M." that H.M.'s hippocampus was non-functional after large sections of his left and right medial temporal lobe were removed. Other types of temporal lobe surgeries, such as tumor removal, can also result in short-term memory loss, according to the NIH.
Degenerative Disease
Another type of short-term memory loss is caused by degenerative diseases. The NIH states that Alzheimer's disease, which results in changes to brain structure, has severe memory loss symptoms. In the early stage of the disease, the patient has problems remembering new information and has issues recalling current events. Degenerative disease memory loss, however, progresses to long-term memory loss in the later stages.
Trauma
The NIH notes that both physical and emotional trauma can cause short-term memory loss. With a head injury, the patient can suffer brain damage with or without a skull fracture. If the impact is on the temporal lobe, short-term memory loss is possible. With a traumatic event, physical damage does not occur to the brain, though brain function can change. The amygdala, part of the limbic system that's also located in the medial temporal lobe, is responsible for emotions and is tied in with memory formation. When emotional trauma occurs, the amygdala goes into overdrive and can cause psychological amnesia; this short-term memory loss can usually be reversed with counseling.
Substance Abuse
Short-term memory loss can also be caused by alcohol and/or drug abuse. The NIH states that substance-related short-term memory loss occurs when a patient uses a substance over a long period of time, affecting brain chemicals and damaging the hippocampus. Certain drugs, like benzodiazepines and barbiturates, carry the risk of short-term memory loss, and excessive alcohol use can result in Wernicke-Korsakoff syndrome, a disorder where the patient can no longer form new memories.
References
- MedlinePlus: Memory Loss
- "Seminars in Neurology: Lasting Consequences of Bilateral Medial Temporal Lobectomy: Clinical Course and Experimental Findings in H.M."; Suzanne Corkin; 1984
- MedlinePlus: Alzheimer's Disease
