Amnesia is a memory condition in which memory is disturbed and it can be defined as the loss of memory. The causes of amnesia can be organic or functional. Organic causes include damage to the brain, through trauma or disease, or use of certain drugs (sedative). Functional causes are psychological factors, such as defense mechanisms. In amnesia some people can't recall stored memories, like their name or what happened last evening, but they may recall the music they learnt or heard in their childhood.
"Selective amnesia is a memory loss in which a person loses a few parts of his memory. Selective amnesia or amnesia depends upon the part of the brain that is affected. Memory is the function of certain parts of the brain and if any part stops working, complete functions will be disturbed," says Dr. PN Renjen, Senior Consultant, Neurology, Apollo Hospitals.
There are several different types of amnesia which can be caused by disease or head trauma. In most cases, amnesia is a temporary condition and is very brief, lasting from a few seconds to a few hours. The two most commonly discussed forms of amnesia are retrograde amnesia and anterograde amnesia. If someone is suffering from retrograde amnesia, he or she cannot recall memories that occurred before the onset of amnesia. Some retain virtually full recall of things, that happened prior to the onset of amnesia; others forget only their recent past.
Amnesia has several root causes. Most of them are because of brain injury related to physical trauma, disease, infection, drug and alcohol abuse, or reduced blood flow to the brain. Infections that damage brain tissue, including encephalitis and herpes, can also cause amnesia.
The central symptom of amnesia is loss of memory for a period of time in the patient's life.
Other symptoms include the following: