re: concussion types: you mentioned global amnesia being incredibly rare as a side effect of head trauma, so i was wondering, how bad would the trauma have to be to induce “i can’t remember anything” amnesia? most info i found relates to memory loss around the time of the trauma, not on total memory loss which really speaks to uncommon it is, but if you have any insight i would love to know! (also from what i gather, you’d lose not only memories but physical skills as well, reading, walking etc)
So, the correct term for what we’re talking about is Retrograde Amnesia. This is the loss of previously created memories. There’s a lot of potential causes, but as with concussions, it’s not about how hard you’re hit, it’s what your brain is doing.
In a lot of cases, it’s not even about an injury; simply, something in your brain doesn’t work right. Your brain stores and recovers a lot of information on a regular bases, and whenever something goes wrong, whether that’s due injury, illness, chemicals, electroshock “therapy,” or psychological factors, it’s amnesia.
The term itself, is a bit misleading, because it’s describing a wide range of similar symptoms under a single header. The term itself is basically just, “can’t remember.” So, technically, if you forgot where you left your keys, and wanted to be overly dramatic, you could call that amnesia. No one else would be likely to agree, but you wouldn’t be completely wrong.
Complete Retrograde Amnesia is incredibly rare. I don’t have a number for this, the rate of incidence is that low. It’s a bit confused, because things like dementia are forms of retrograde amnesia. So, this can become a question of severity.
The one I do have numbers for is Transient Global Amnesia. I’ve actually had the privilege of watching an entire TGA event from start to finish. The rate of incidence there is about 5:100,000, and events usually last for less than a day.
TGA is complete anterograde amnesia, with mild retrograde amnesia. In this case, the patient was unable to form new long term memories for about six to eight hours, and while the event persisted they were unable to recall events in the previous nine months to a year. This lead to some remarkably repetitive conversations. After the event completed they were unable to recall events from roughly six hours before the event started until after it’s conclusion, and my understanding is they never recovered those memories.
During initial onset, the immediate fear was that the patient was experiencing a stroke. Given the symptoms, that was a reasonable concern.
Lit says that the patient should be able to remember, roughly, the last five minutes during the event. That sounds consistent with what I saw, but I didn’t time it.
So, there’s a term up there, “anterograde.” Let’s describe these. Retrograde simply means, “moving backwards.” Outside of amnesia, you’ll most often encounter this regarding the movement of celestial bodies. Under the geocentric model of the solar system, planets which appeared to reverse course were a serious puzzle, and the phenomena was described as, “retrograde motion.” When you add the fact that planets orbit around the sun, and not the earth, it makes perfect sense. They’re not reversing course, it’s simply a function of the planets’ orbits creating the illusion of reverse motion. Planets are still described as being “in retrograde,” to indicate that their apparent motion has reversed from the perspective of earth, even though we now understand why this happens.
Similarly, anterograde simply means “moving forward.” (Worth knowing that, while retrograde derives from Latin, and has been around since, at least, Middle English, anterograde is a modern word.) When dealing with amnesia, anterograde is the inability to form new memories. IE: “Without memories moving forward.”
As with any other form, anterograde amnesia can be there result of a number of different causes, including some illnesses, chemical reactions, brain tumors, injuries, and stroke.
Anterograde amnesia can also be experienced as a result of being put under general anesthesia. This means, I’ve probably experienced this first hand, but have no recollection of it.
A concussion can result in either anterograde, retrograde, or a combination of both forms of amnesia. Usually associated with damage to the medial temporal lobe. Note: this part of your brain does a bit more than just store memories. It’s also responsible for spacial cognition. If I remember correctly, but I can’d find reference to verify right now, damage to the medial temporal lobe also result in epileptic seizures, and loss (or at least impairment) of emotional control.
Since we’re talking about neural structure, and way out of my depth already, let’s talk a little more about memory. You have at least two distinct types of memories. Episodic memories are things you experience. If you stop and think back to something that happened, that’s an Episodic memory. Semantic memories are skills, and abstract knowledge. While knowledge derives from episodic experiences, you actually store this stuff differently. (I’m not clear on the exact, chemical or biological distinction here.) This is important to understand when talking about amnesia, because what you have seen and what you know are different kinds of memories. So, the idea that someone can’t remember who they are, but still has all their knowledge and skills, isn’t that far fetched. Except for the part where they can’t remember anything about who they are.
I’m going to stick a note in here: You asked about walking, that’s not a memory. Your brain is pretty well hardwired to do that. There’s actually a number of basic actions and functions of fine motor control, that have nothing to do with memory. Some of this stuff will atrophy if you don’t use it, but you’re not going to forget it. One of the more interesting ones is swimming, as infants are born with a reflexive ability to (attempt to) swim. This atrophies pretty quickly, but, it’s interesting.
One form of amnesia we’ve all experienced is infantile amnesia. This just discusses the phenomena where people do not (generally) remember the first three to five years of their lives. (There are exceptions, but those are rare.) This is simply a function of neural development, and may be tied to development of language skills.
There is one last variety you should familiarize yourself with: Dissociative amnesia. This a psychologically derived. It includes things like repressed memories and fugue states. The patient decides (at a sub-conscious level) not to remember something. This can be because the event is so traumatic they refuse to acknowledged it, or any number of other factors. In some extreme cases, the patient rejects themselves. They forget everything. Technically the memories are still intact, it’s not they put their brain on a bulk eraser and nuked it. They simply will not interface with those memories. In some ways can be pretty, “laser guided,” because the patient is trying to protect themselves, and are the best suited to know if something’s going to cause problems.
As a therapist, there a fairly decent argument not to probe someone with dissociative amnesia too deeply, unless they really are asking you to. We don’t talk about this much, but when it comes to psychology and the Hippocratic oath, if the patient is not being harmed by their issues, or harming others, you don’t mess with them. A patient with a dissociative amnesia who is happy with who they are, is not someone who “needs to be dragged back to face themselves.” Chances are, there were really good reasons their mind went, “nope,” duct taped the whole thing in a box, and chucked in the back of a closet. If the patient comes to you distressed because they can’t remember who they were, that’s different. If the patient simply can’t remember who they were, but is fine who they are, do no harm.
Okay, that’s amnesia, let’s talk about why you should never use this stuff in your writing.
The amnesiac point of view character is a very, very, useful trope. It’s too useful. This is why it has become cliche.
When you create a new world, you as the writer, know the rules, you know players, you know all the moving pieces. Your audience knows nothing. At this point, you have to decide how to introduce your audience to your world. What better way than picking a PoV character who remembers nothing and needs to be spoon fed the backstory as they go along? The audience, and the character, will acquire information at the same rate as they progress through the story.
Amnesiac characters can also justify a lot of exposition. If they know nothing, then they’ll have to have all of this explained to them. But, you might have just noticed a problem, that’s not how amnesia works (in most cases.)
Someone might not remember that the person they’re talking to killed their sister, but they are going to remember the factions and other political considerations that govern the other character’s motivations. Some details will be missing, but the abstract knowledge should be intact.
Many amnesiac PoV characters aren’t really amnesiac, they’re simply audience proxies who are unfamiliar with the backstory, blundering around, as the world is gradually filled in.
Now, having just picked at this a bit, it works very well. Especially if you, (as the writer) are not yet comfortable with the setting. The problem, and the reason I said, “don’t use this,” is because it has become cliche, due to overuse. You can’t pick a fantasy novel off the shelf without accidentally knocking over eighteen more about edgy amnesiac heroes wandering around someone’s home brew D&D campaign. It gets worse when you get into other media.
There are some other good uses. One is an amnesiac character investigating themselves. There’s a lot of this in the thriller genre. Much like the case above, this is a bit cliche, but is also a situation with some unique options. Robert Ludlum’s The Bourne Identity comes to mind as an interesting variant of this. Though the amnesiac spy has been done to death since.
Amnesia is a very useful, very potent, tool for a writer. It’s one you do not want to abuse, because, when misused, it will deprive your story of its uniqueness. If you have to chose between an amnesiac PoV, or committing to a PoV character that’s up to speed, pick the latter. It may not seem as easy, but it gives you more control than your realize.