Retrograde amnesia is a form of amnesia where someone is unable to recall events that occurred before the development of the amnesia, even though they may be able to encode and memorize new things that occur after the onset.
|Did You Know?|
|Perhaps the best-known example of retrograde amnesia actually turned out to be a scam.|
“Philip Staufen” (actually the name of a medieval German king, but it was the first name the man came up with when he woke up), also known as Mr. Nobody, was a man, in his late twenties and with a slight Yorkshire English accent but no other identification, who awoke in a Toronto hospital in 1999 with what appeared to be severe retrograde or global amnesia.
After various attempts to obtain Canadian citizenship and to legally change his name, he turned out to be a Romanian called Sywalkd Skeid, and to exhibit no clinical evidence of amnesia at all.
The famous anterograde amnesia case is known as “H.M.” also suffered moderate retrograde amnesia, and could not remember most events in the year or two before surgery, nor some events up to 11 years before.
The British musician Clive Wearing suffers from an acute and long-lasting case of both anterograde amnesia and retrograde amnesia.
Retrograde amnesia usually follows damage to areas of the brain other than the hippocampus (the part of the brain involved in encoding new memories), because already existing long-term memories are stored in the neurons and synapses of various different brain regions. For example, damage to Broca’s or Wernicke’s areas of the brain, which are specifically linked to speech production and language information, would probably cause language-related memory loss. It usually results from damage to the brain regions most closely associated with declarative (and particularly episodic) memory, such as the temporal lobe and prefrontal cortex. The damage may result from a cranial trauma (a blow to the head), a cerebrovascular accident or stroke(a burst artery in the brain), a tumour (if it presses against part of the brain), hypoxia (lack of oxygen in the brain), certain kinds of encephalitis, chronic alcoholism, etc.
Typically, episodic memory is more severely affected than semantic memory, so that the patient may remember words and general knowledge (such as who their country’s leader is, how everyday objects work, colours, etc) but not specific events in their lives. Procedural memories(memory of skills, habits and how to perform everyday functions) are typically not affected at all.
Retrograde amnesia is often temporally graded, meaning that remote memories are more easily accessible than events occurring just prior to the trauma (sometimes known as Ribot’s Law after the 19th Century psychologist Théodule-Armand Ribot), and the events nearest in time to the event that caused the memory loss may never be recovered. This is because the neural pathways of newer memories are not as strong as older ones that have been strengthened by years of retrieval and re-consolidation. While there is no actual cure for retrograde amnesia, “jogging” the victim’s memory by exposing them to significant articles from their past will often speed the rate of recall.