anquex asked: I've heard that there's two types of amnesia: anterograde amnesia, where a person can't remember new things; and retrograde amnesia, where a person can't recall pre-existing memories. From reading your previous posts, I'm guessing the former is due to a problem more to do with the hippocampus while the latter is perhaps from neurodegeneration. What happens with temporary amnesia then? It's common in movies to have a character be in a car accident and temporarily loose their memories only to regain them latter. How do they remember those memories again? Is it from restored function of the hippocampus, or regeneration of connections between neurons or something? And do people in such situations often forget just a certain person or certain events instead of a broad range of memories, or is that just a preference of script writers and directors? Sorry for slamming all these questions on you. I just find your explanations really easy to understand so I hope you don't mind me asking.
First of all, I apologize for not replying to your questions sooner. I had no idea this message function even existed, much less that I had messages in it. I hope you didn’t ask these questions horribly long ago. They are wonderful questions!
You are totally right. Anterograde amnesia, where new memories cannot be made, is due to hippocampal damage, as the hippocampus encodes new memories. Retrograde amnesia, where a person loses memories from past events, is due to neurodegeneration or damage to the cortex. The hippocampus encodes the memories and then stores them in cortex (essentially the rest of the brain). With hippocampal damage, there can be some problems with “old” memories of up to about a year back, if they have not already been completely stored in cortex yet. This is not the same as complete retrograde amnesia, which is due to cortical damage.
Temporary amnesia rarely occurs in the real world, unless it is for less than a day. This can be due to brain swelling, which would also cause general cortical impairment and disorientation. Usually, when memories are lost, they are lost forever. The temporary amnesia that screenwriters use is largely fictional (though it is theoretically possible). When screenwriters use deletion of a specific person or event from mind, this is more akin to the idea of repressed memory, which has not been scientifically supported or studied yet (see this post for more information).
These are wonderful questions, and I hope this helps clarify things for you! Apologies again for not seeing it sooner (find something new every day).
