What amnesia is
- Amnesia is memory loss caused by damage to the brain through injury, illness or trauma, not by ordinary forgetting.
- It comes in two types, and the difference between them is which memories the damage affects.
- The dividing line is always the moment of the injury or illness, so ask whether the lost memories come from before it or after it.
Retrograde amnesia
Definition
Retrograde amnesia
A loss of memories formed before an injury, illness or traumatic event, while the ability to form new memories is usually kept.
- In retrograde amnesia nothing is wrong with the ability to learn, so the problem is reaching the past rather than building a future.
Symptoms of retrograde amnesia
- You cannot recall events from a stretch of time leading up to the injury or illness.
- The most recent memories before the event are usually the worst affected.
- Older and well-practised memories, such as your own name or your childhood, often survive.
- You can still take in and remember new information after the event, because forming new memories is not what has been disrupted.
Example
- After a head injury in a car crash, a woman cannot recall the journey or the weeks before it.
- She still knows her own name, her family and her job from years earlier.
- She learns the names of the hospital staff over the following days without difficulty.
Anterograde amnesia
Definition
Anterograde amnesia
An inability to form new long-term memories after an injury, illness or traumatic event, while memories from before it are usually kept.
- In anterograde amnesia the damage stops new information moving from short-term memory into long-term memory, so it is never stored.
Symptoms of anterograde amnesia
- You cannot learn and hold on to new facts, faces or events after the injury or illness.
- You can keep something in mind for a few seconds, but it slips away as soon as your attention moves.
- You may be introduced to the same person every day and greet them as a stranger each time.
- Memories formed before the event usually remain, because they were already safely stored.
Example
- After a brain infection, a man can describe his childhood and his old job in detail.
- He cannot say what he ate an hour ago or recognise the room he moved into last month.
- He repeats the same question every few minutes because the answer never reaches long-term memory.
Telling the two apart
- Ask when the lost memories are from, because if they date from before the event it is retrograde amnesia.
- Ask what the person cannot do now, because if they cannot lay down new memories it is anterograde amnesia.
- Watch for both at once, because severe damage can open a gap in both directions.
Common Mistake
- Do not swap the two, because retrograde is the lost past and anterograde is the blocked future.
- Do not write that all memory is gone, because usually only one direction is affected.
- Do not describe amnesia as forgetting, because it follows damage to the brain rather than a lack of rehearsal.
Turning this into marks
- A definition needs the direction in the sentence, so say memories from before the damage or memories formed after it rather than just memory loss.
- When two symptoms are asked for, make them genuinely different, because the same symptom reworded counts once.
- The mark most often lost is naming the type in a scenario without quoting the detail that shows the direction.
Self review
- Define retrograde amnesia in one sentence that makes the direction clear.
- Define anterograde amnesia in one sentence that makes the direction clear.
- Give two symptoms of retrograde amnesia and two symptoms of anterograde amnesia.
- A man after surgery can recall his wedding twenty years ago but cannot remember meeting his physiotherapist yesterday, so name his type of amnesia and say which detail told you.
