Nobody in their right mind would ever accuse Hollywood of being a halfway decent source of scientific information. Understandably so, facts are twisted to service the plot, real science merges absurdly with pseudoscience, and the laws of physics are largely ignored as action heroes perform feats that defy gravity and logic. Which is completely fine- Hollywood is an entertainment business, and nobody comes to an action movie to gain a deeper understanding of the human brain. However, once in a while a movie will be both entertaining and surprisingly accurate.
Memento is a thriller that takes us inside the mind of Leonard Shelby, a hero suffering from amnesia as he single-mindedly pursues the man who killed his wife. Amnesia is great dramatic fodder for Hollywood, although its portrayal is usually improbable at best. Heroes are bopped on the head and wake up remembering nothing of their past- until another head trauma or plot convenience miraculously gives them back their memory. In most movies, amnesia is simply another plot device.
However, Memento is different. Unusual for Hollywood, the hero suffers from anterograde amnesia, where he remembers with perfect clarity his life before the attack that left his wife (in his recollection) dead and his brain damaged by blunt force trauma. However, Leonard cannot form any new memories, and spends the entirety of the movie in this state- leaving himself notes on his own body to give himself clues, and forgetting character reveals and betrayals midway through a scene. Several scenes show him frantically jotting down something important on a photograph before his amnesia forces him to forget. The film has a fragmented, twisty feel that actually does a lot of justice to real cases of anterograde amnesia.
In Latin, the word for “seahorse” is hippocampus. Located under the medial temporal lobe, the hippocampus is highly involved in long-term memory. It is hypothesized that the hippocampus serves as a “gateway” for new memories- they must travel through the hippocampus before being stored permanently as long-term memories in the brain. Damage to the hippocampus, whether by injury, infection, or chronic alcoholism (Korsakoff’s syndrome) can result in anterograde amnesia. Like in Memento, people with anterograde amnesia may be able to access old memories already laid down in long term storage. However, they will not be able to form new memories, due to failures in encoding and storage. A famous case of anterograde amnesia is patient H.M. – apparently an inspiration for the director of Memento.
Before he became a vigilante hunting down “John G”, Leonard was an insurance investigator. In light of his amnesia, it seems unlikely that Leonard would be able to maintain any of the new skills he learned hunting for John G. However, even this can have a cognitive basis. Research has shown that people with retrograde amnesia can retain their procedural memory, which is involved with learning skills and habits. This is because the hippocampus is not involved in procedural memory the same way it is involved in declarative, or autobiographical, memories.
On top of being a stellar movie in its own right, Memento has the additional value of being an atypically cognitively solid movie by Hollywood standards. In fact, the most improbable thing seems to be why Leonard wasn’t under hospital care or study, instead of being free to track down a rapist.