Recently I watched the movie Memento and it brought back memories of HM. HM, a famous neuropsychological patient (full name not revealed to preserve his privacy) suffered from amnesia, whose case heralded a whole new slew of findings on human memory.
In early 1950’s HM was treated for epilepsy by having both his hippocampi (a small part of the brain, named for the fact that it is shaped like a sea-horse) removed. Something strange happened. From that point onwards HM was unable to make new memories. He froze in time. He knew who he was (so it was not a case of forgetting his past). He simply could not form any new memories from that day onwards. A few psychologists discovered his case and so started a momentous period in memory research.
The movie Memento shows a somewhat similar case, that of Shelby who is unable to form new memories. His way of dealing with it (amnesia) is to take pictures and write notes in order to remind himself of events and people.
Both HM and Shelby have antegograde amnesia (where you cannot form new memories). This is different that reterograde amnesia (where you cannot recall some or much of your previous memories). Memento gets it wrong when Shelby says: “I don’t have amnesia. I know who I am. I just can’t form new memories.” Well, he does have amnesia, its simply a different type of amnesia than movies tend to deal with. Reterograde amnesia is a favorite of movie makers (both Hollywood and Bollywood), perhaps because it offers an easier opportunity for simplistic drama – someone has a loss of identity, they redefine themselves, or their past catches up with them. Ah, the dramatic possibilities!
In my opinion, Memento also gets it wrong when Shelby says that he has short term memory problems. His problem is not with short term memory itself – it has to do with the transfer of memories from the short term to the long term store. So he can remain in the moment and retain whats happening around him. But he forgets everything as soon as he is out of that moment.
Steven Johnson’s excellent review of Eternal Sunshine of the Spotless Mind, refers to Memento as based on an older model of memory formation, saying that the newer model integrates emotion more deeply. While his contention about emotion is correct, I don’t think that the model of memory exposed by Memento is any less valid today. The model might be more refined now, but there is no change to the basic premise of Memento – very limited damage to certain parts of the brain can cause profound amnesia. Such damage can be global, i.e., it holds true for both emotional and non emotional memories.
Steven also writes
The emphasis on feeling over data processing puts Eternal Sunshine squarely in the mainstream of the brain sciences today. We now know that the brain stores emotional memories very differently from unemotional ones…Particularly traumatic memories appear to be captured by two separate parts of the brain: the hippocampus, the normal seat of memory, and the amygdala, one of the brain’s emotional centers. People incapable of forming long-term memories thanks to hippocampal damage can nonetheless form subconscious memories of traumatic events if their amygdala is intact. Someone suffering from the Memento condition would likely have a feeling of general unease encountering a person or a situation that had caused them harm in the past, though they wouldn’t be able to put their finger on what was making them uncomfortable.
Here, Steven is bringing up the difference between explicit and implicit memory. However, he seems to say that implicit memory (that lie below consciousness) is relevant primarily in an emotional context. That is not correct. Someone like Shelby (in Memento) should be capable of forming implicit memories in a non-emotional context as well. For example, he should be able to learn new skills such as riding a bike. A story told to by my advisor in Graduate School will illustrate this: There was once an amnesic patient and a graduate student. Everyday, the student would meet the patient and introduce himself since the patient never remembered. One day the graduate student told the patient a joke. The patient laughed out loud and said “thats funny, I have never heard that”. Next day, the student repeated the same joke. The patient laughed, but not so loudly, though he still said that he had never heard the joke before. The day after that, the student repeated the joke again. And the next day. Anyway, soon the patient stopped laughing entirely though he never remembered having heard the joke.
Explicit memory for the joke was impaired, implicit memory was fine. Implicit memory system engages many brain structures not just the parts of the brain having to do with emotion, i.e., the amygdala.
Talking of memory and movies, here are some of the movies that use amnesia as a theme. Do you know of any more? Please add to the list. Maybe I will do a Amnesia retrospective…
Paycheck: Ben Affleck is an industrial spy who gets his memory wiped out after every job (so that he cannot pass on any secret information.)
The Bourne Identity: Bourne is a CIA assassin who suffers amnesia and loss of identity and then suspects that he may be a terrorist.
The Long Kiss Goodnight: Geena Davis is a schoolteacher who has amnesia. When she is able to recall her past, she realizes that she was a CIA agent. (I really enjoyed this movie)
The Manchurian Candidate: An American soldier captured in Korea has been brainwashed, made an agent of the enemy, and his memory for this episode has been erased. Back in the USA, memories of this incident seep out through dreams. (Want to see this)