Normal memory function involves many parts of the brain, and any disease or injury that affects the brain can interfere with the intricacies of memory. Amnesia can result from damage to brain structures that form the limbic system, which controls your emotions and memories. These structures include the thalamus, which lies deep within the center of your brain, and the hippocampal formations, which are situated within the temporal lobes of your brain.

Amnesia caused by brain injury or damage is known as neurological or organic amnesia. Possible causes of neurological amnesia include:

  • Stroke
  • Brain inflammation (encephalitis) resulting from infection with a virus such as herpes simplex virus or as an autoimmune reaction to cancer somewhere else in the body (paraneoplastic limbic encephalitis)
  • Lack of adequate oxygen in the brain (for example, from heart attack, respiratory distress or carbon monoxide poisoning)
  • Long-term alcohol abuse leading to thiamin (vitamin B-1) deficiency (Wernicke-Korsakoff syndrome)
  • Tumors in areas of the brain that control memory
  • Degenerative brain diseases, such as Alzheimer's disease and other forms of dementia
  • Seizures
  • Electroconvulsive therapy, a procedure in which electrical currents are passed through the brain, sometimes used to treat certain mental illnesses
  • Certain medications, such as benzodiazepines

Head injuries, such as those sustained in car accidents, can lead to confusion and problems remembering new information, especially in the early stages of recovery — but usually don't cause severe amnesia.

Another rare type of amnesia, called psychogenic or dissociative amnesia, stems from emotional shock or trauma, such as being the victim of a violent crime. In this disorder, a person may lose personal memories and autobiographical information, usually only briefly.

Oct. 11, 2011