Finding Dory’s Memories: The neuroscience behind Disney Pixar’s Finding Dory

Warning: Minor spoilers if you have not yet seen the movie!

Summary of Finding Dory

Finding Dory picks up a little while after Finding Nemo ended. Nemo is still a kid and going to school with Mr. Ray. Rather than following Marlin, Nemo’s dad, the movie follows Dory the Blue Tang who sufferers from short-term memory loss. Also, rather than Marlin trying to find Nemo again, Dory is trying to find her parents. This is extremely difficult due to Dory’s short-term memory loss. Some very old memories of Dory’s begin to come back to her and she feels an urge to leave the safety of the reef and seek out her parents across the sea. But, without robust memories, Dory has to rely on gut instincts to navigate back to where she thinks her parents may be. Through a fun filled adventure with help from old friends from the Finding Nemo, like Crush the turtle, and new friends, like Hank the Octopus, Dory sets out to find her parents.

Different types of memories

Before getting into Dory’s short-term memory loss I think I should first explain different types of memories and how they work. There are three primary types of memory in the conventional sense of the word: short-term memory, working memory, and long-term memory. A fourth type of memory, procedural memory, exists as well. Procedural memory primarily has to do with motor movement, like riding a bike, throwing a ball, or swimming. I’ll leave out procedural memory because Dory seems to have no problems with swimming!

 

 

Short-term memory

Short-term memory is a form of memory which allows us to remember about 7 +/- 2 items for approximately 18 seconds. A good analogy for short-term memory that I like to use is a conveyor belt moving along in your brain. Information falls onto the conveyor belt, either through our senses, like sight or sound, or internally from our own thoughts. The conveyor belt is pretty small, it can only have 5 – 9 information “boxes” on it at one time. Once on the conveyor belt, our brain has about 18 seconds to use this information otherwise it will fall into an incinerator where it cannot be recalled from ever again. For example, you may be day dreaming in class about all the other things you could be doing other than learning about the ancient Greeks when your teacher calls on you to answer a question. Even though you were not attentively listening, you may be able to vaguely remember the question because the auditory information is still on the short-term memory conveyor belt. This allows you to at least make up a plausible answer to the question. Short-term memory is something we really do not ‘think’ about; we just have access to it. However, to truly remember information it has to be taken off the short-term memory conveyor belt.

Working memory

Working memory and short-term memory may seem similar but they are actually quite different. Like I said above, short-term memory is a passive process; we don’t ‘think’ about it, it’s just there for us to access. Working memory is the opposite, it is an active process we have to think about. For example, keeping directions in your head. You may mindfully rehearse them a few times to get them to “stick”. Back to the conveyor belt analogy, working memory is like robots picking information off the conveyor belt to use for some goal (like getting to the ice cream shop). But, if the robots are not constantly getting commands from the main computer (your conscious mind) to tell them what to do they may drop the information in the incinerator too. But, if the robots use this information in a meaningful way, they will likely transport it over to a shelf for long-term storage.

Long-term memory

Disney’s Inside Out does a beautiful job of depicting what long-term memory is like in the brain. Memories are not stored in one location but rather get stored all over the brain. Long-term memory is like a huge warehouse full of shelves which have memories on them placed there largely by working memory robots. Each time a memory is brought to long-term storage it also gets some labels on it. For example, your memory of seeing Finding Dory may be tagged with what movie theater you saw the movie at, what snacks you had, and who you were with. Our brains keep similar memories grouped together. So, if you see Finding Dory with your mom, the memory of seeing the movie will be placed in a part of the warehouse where all the other memories of your mom are. There are also the rare times when a robot decides on its own to take something off the conveyor belt and put it in long-term storage. This happens a lot with catchy pop songs for some reason; maybe the robots like to get their groove on!

 

 

Dory’s short-term memory loss

Memory loss can take many forms which are often benign. Not remembering where you put your phone, forgetting the name of that person you met 5 minutes ago, not being able to recall what you learned about the ancient Greeks in 7th grade; all of these forms of forgetting are normal and natural. However, some forms of memory loss can be severe and debilitating. For example, a primary symptom of Alzheimer’s disease is long-term memory loss. People in the late stages of Alzheimer’s find it difficult to remember what year it is, who the president is, and even who their family is. On top of long-term memory loss, they often are unable to form new memories.

Memory loss has many causes. Neurodegenerative diseases like dementia can cause memory loss. Bad head injuries, like concussions, often cause memory problems such as not being able to remember the few minutes, hours, or even days prior to the concussion. Other trauma to the brain can cause forms of memory loss. For example, patient H.M. (full name Henry Molaison) had his medial temporal lobe, a part of the brain vital to forming new memories, removed in an attempt to cure his horrible and frequent seizures. His seizures were cured however he was not able to form a single new memory after the surgery. For example, Henry could remember his childhood house perfectly but could not describe the house he lived in now. Henry was not like Dory though; his short-term and working (and procedural) memory were fully in tact. It was as if the robots that were suppose to move things to long-term storage did not know here to put the memories, so they just put them in the incinerator.

Dory, as far as we know, was born with short-term memory loss. In Dory’s brain it is like her short-term memory conveyor belt is moving very fast and is very small. Also, it seems like she does not have too many working memory robots in her brain. Dory often forgets what she is taking about and what she is doing; as if her working memory robots are dropping memories all the time. Furthermore, since Dory cannot remember things in the short-term she has a hard time forming long-term memories. It is very difficult for her brain to transfer memories from the fast moving short-term conveyor belt out to long-term storage. But as we see in the movie, Dory does have long-term memories, they’re just hard to find.

Dory’s lost memories: A loss of memory or misplaced memories?

There are two theories on why we lose memories and both are probably correct. One theory is that memories are truly lost and gone forever. For example, in Inside Out, old and faded memories are sometimes thrown out of long-term storage; never to be accessed again. Another theory of memory loss is that the memories are still in the brain, they are still sitting on the shelf, but our robots do not know where to find them. However, if the right inputs come into the brain, our memory recall robots may just be able to find those lost memories. This seems to be the case with Dory’s memories. Throughout the movie Dory remembers more and more about her past but only when something in the world prompts her. For example, she may see a sign which she had seen when she was growing up! Or she hears the familiar voice of a whale friend and all her memories come rushing back.

The process of remembering something is called “memory recall”. During recall, our brain reactivates the neurons which are responsible for our memories. But like I said before, memories in long-term storage have labels on them and memories which have similar memories are stored with each other. So, when Dory hears a familiar voice, all the memories which have the label “whale speak” are likely to be recalled. The sound information that comes onto the short-term memory conveyor belt and is picked up by working memory robots helps the robots to find those previously lost memories. In other words, Dory’s whale friend’s voice helps to find the memories Dory cannot find just by trying to remember; she needs a sensory input, her pipe pal’s voice, to find and reactive those old memories.

Hover over the below image to see how a memory cue can strengthen memory recall.

 

This process of finding old memories by a sensory information, also known as memory cues, is all about matching patterns. At the level of the brain these patterns are distinct groups of neurons and their activity. Zoomed out a bit these patterns are just like a matching game. When the voice of Dory’s whale friend comes into her ears and falls onto her short-term memory conveyor belt, her working memory robots will take this information and search through long-term storage for other memories that match. Without sensory information though, without a memory cue, Dory’s robots are not able to find old memories like most people can.

As Dory gets closer and closer to home, she finds more and more cues. With more cues, she can find more of her old memories which she thought were no longer with her but can now be found.

Is Dory’s condition real?

Dory’s memory condition is a bit complex and I do not know of any one memory deficit disease, or Amnesia, which could fully encompass her (though I am not a clinical neuroscientist so if there is one out there please do let me know!).

The two most common forms of amnesia are Retrograde Amnesia and Anterograde Amnesia. Anterograde amnesia is the inability to create new memories, usually after a traumatic event or severe damage to the brain. People with Anterograde amnesia however have no problems with remember events that happened before the trauma or injury. This is what Patient H.M. had due to his surgery to fix his seizures

Retrograde is the opposite. People with Retrograde amnesia have no problems with forming new memories, again usually after some trauma, but cannot remember anything that happened prior to the trauma. These two amnesia are not mutually exclusive and can be present at once, as was the case with Patient R.B.

Dory seems to have a bit of both. In Finding Nemo it seemed like she had full Retrograde amnesia as she had no idea where she came from or any memories of her past. She also seemed to have very bad Anterograde amnesia however she was able to form some new memories, for example learning that Nemo and Marlin were her friends but only after a very long time being together. In Finding Dory it seems as though the severity of Dory’s Retrograde amnesia is lessening because she is now able to remember some things from her past. This also implies that she does have the ability to form memories, and always had the ability to form memories, but had a very difficult time retrieving them. It is only with rich sensory cues is she able to access her old memories.

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All images from Finding Nemo, Finding Dory, and Inside Out are copyright of Disney/Pixar

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This work by Blake Porter is licensed under a Creative Commons Attribution-Non Commercial-ShareAlike 4.0 International License

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