Updated: Sep 23, 2021
Memory loss, otherwise known as amnesia, is a common trope used in film - but how accurate are the stories we see?
Whether it’s your Facebook feed, posts from Instagram influencers or new Netflix releases, we’re constantly bombarded with information. Much of this may not reflect the reality of the world we live in, so it is more important than ever to think critically about what you see on the big (or small) screen.
Hollywood takes its liberties when depicting science and medicine in media - and the case of amnesia is no exception. Although many films do not make the distinction, we should understand that memory can be classified in many ways - one of which is ‘declarative’ and ‘nondeclarative’ memory . Declarative memory is conscious and can be ‘declared’ i.e. facts (semantic memory) and events (episodic memory). Conversely, nondeclarative memory is unconscious and cannot be expressed in words, such as motor and cognitive skills, also known as procedural memory .
Like memory systems, memory loss can also be categorised, as shown in Figure 1. Anterograde amnesia occurs when individuals are unable to consolidate information and experiences into new long-term memories . Conversely, retrograde amnesia occurs when individuals have difficulty remembering past events and familiar information .
Figure 1: Summary of the difference between retrograde and anterograde amnesia. 
Now that we’ve defined these terms, let’s step through the structure of a generic film and debunk some common myths about amnesia.
1. Orientation: How does the amnesia occur?
Fiction: Amnesia is often caused by extreme head injuries.
At the start of The Vow (2012), Paige is involved in a car accident and cannot recognise her husband after she wakes up from a coma.
Fact: While the situation in The Vow is based on a true story and can definitely occur, the film doesn’t address all the effects of a traumatic brain injury (TBI) like this. When a TBI leads to amnesia, there are often other effects on personality and behaviour which are not factually addressed in The Vow, such as impulsiveness and irritability .
Furthermore, while amnesia can be caused by head trauma, as almost always is the case in films, there are many other causes too. These include psychiatric disorders, brain infections, stroke, long-term alcohol consumption, or surgical procedures where important memory-related structures are damaged or removed .
There is a famous case of a patient, H.M., who had severe epilepsy and underwent surgical removal of brain structures responsible for the seizures, including his hippocampus (shown in Figure 2) . The good news was that his seizures vanished. On the flip side, he suffered from severe anterograde amnesia, and had moderate retrograde amnesia . Interestingly, after the removal of his hippocampus, H.M. could not remember declarative information, but his nondeclarative memory was intact . This demonstrates that declarative memory requires the hippocampus, and further studies have shown that non-declarative memory draws heavily from regions like the cerebellum .
Figure 2: Part of the brain is dissected to show the location of the hippocampus, as indicated in blue, which lies deep in the temporal lobe. This region is key for remembering facts and events, such as the first day of high school. 
2. Complication: What are the implications of amnesia?
Fiction: Amnesia often results in identity loss.
In the Bourne films (2002-2016), the protagonist Jason Bourne has forgotten his past life as an assassin, and is even unable to recall his own name.
Fact: Bourne’s condition is more reminiscent of a specific, rare and reversible form of amnesia called dissociative amnesia, typically caused by severe emotional stress or trauma .
Amnesia rarely impacts our sense of self. Our name, age, the suburb we live in, feelings, thoughts and core beliefs are all preserved . One of the main areas involved with higher-order cognitive processing, such as forming our identity as individuals, is the medial prefrontal cortex, located towards the front of our brain . Scientists have found that this brain region is active when people think about themselves, their personality traits or their emotions . People with damage to this region find it difficult to reflect on themselves and their interests. So, although forgetting one’s identity is a convenient plot device in movies and shows, it only occurs in one rare form of amnesia.
3. Resolution: What happens to the memories of amnesiacs?
Fiction: Amnesiacs eventually recover their lost or repressed memories, which they are then able to piece together and vividly remember.
Memento (2000) is centred around memories of a traumatic event which lead to the injury of the protagonist, Leonard, and eventually fuels his revenge plan against the perpetrators.
Fact: In reality, it’s highly unlikely that Leonard would remember these events; when under extreme stress or trauma, short-term memories are more susceptible to being lost before being consolidated into long-term memories . The ability to retrieve repressed traumatic memories is a topic of controversy, but currently there’s no reliable or proven way to do this . However, if the hippocampus is removed, new memories can’t be processed at all, as H.M. experienced post-surgery until his passing in 2008.
Memento (2000) is structured so that the film moves backwards to capture how disorienting and confusing daily life can be for someone with anterograde amnesia. Similarly, in the film Finding Nemo (2003), Dory’s confusion and disorientation is actually quite an accurate depiction of anterograde amnesia and how the condition can be distressing for patients, their carers and families .
Amnesia is evidently a complex topic, but hopefully the next time you sit down to watch a movie or a TV episode, you can silently praise the writers if they get the facts right. Otherwise, just forget about it.
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