Now how

How do people lose their memories?

What?

Memory loss appears in the media in a variety of forms.  In The Bourne Identity, Jason Bourne suffered from extreme memory loss, unable to remember anything about his past but finding that he is fluent in several languages and able to perform unusual physical feats.

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Dory from Finding Nemo has short-term memory loss, unable to remember things that have occurred over the past few minutes (with the exception of “P. Sherman, 42 Wallaby Way, Sydney).

Other times, rather than constantly being burdened with forgetfulness, memory loss is depicted as purposeful – a specific, targeted group of memories being removed from one’s mind, such as how the firm Lacuna, Inc. in Eternal Sunshine of the Spotless Mind allows people to erase their memories of a certain person.  In fact, the two main characters, Clementine and Joel mutually erased each other from their minds following the end of their relationship (you’ll have to rent the movie to see how this plays out . . . )

In all of these instances, the idea of memory loss is used differently, but they each have some scientific basis in the different forms of amnesia.

Why?

As we’ve seen, pop culture loves using memory loss as a plot device, and it’s not difficult to understand why. It’s incredibly versatile, capable of playing on our innate fear of not knowing something important or, on the contrary, quite comical when others know something simple that we don’t. Most importantly, though, memory loss serves as an appealing driving force behind story development: the pathway to discovery.

How?

It’s a common misconception that the only type of amnesia is Jason Bourne’s in which all memories prior to a certain point are wiped out. In truth, amnesia can take many different forms.

Bourne’s condition is known as retrograde amnesia in which the patient is unable to remember events that happened prior to the trauma that caused the memory loss, but can remember all new events normally.

amnesia4On the other hand, anterograde amnesia is the exact opposite in which the patient cannot remember any new memories following the trauma causing the memory loss. Information that should be stored into short-term memory disappears, but the patient can remember events that occurred before the injury with no difficulty. This is depicted in the movie 50 First Dates, where Drew Barrymore’s character gets into a terrible car accident, develops anterograde amnesia, and consequently believes that every new day is the same day as the accident.

These are the most common forms of amnesia. Other forms include transient global amnesia, which is a temporary loss of all memory, traumatic amnesia, the loss of memory as a result of a hard blow to the head, and hysterical (fugue) amnesia, in which patients forget not only their past memories, but their own identity as well to the point where they cannot recognize themselves in the mirror (Nordqvist).

The one feature all forms of amnesia have in common is that they are caused by some sort of disease or trauma to the head. Memory function involves many parts of the brain so anything that affects the brain risks affecting one’s memory. The frontal lobe, known as the prefrontal cortex, processes short-term memories and retains non-task-based long-term memories. The temporal lobe helps in the formation of long-term memory. The medial temporal lobe (the inner part of the temporal lobe) specifically is believed to be involved with episodic memory, or memory of specific events and experiences.

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Deep within the medial temporal lobe is the limbic system, which is comprised of several smaller organs, several of which are also relevant to processing memory. For example, the hippocampus is involved in the transference of memory from short-term to long-term and controls spatial memory and behavior. Another limbic system organ, the amygdala is the primary organ for processing the memories for emotional reactions and social behavior.

The cerebral cortex also includes the basal ganglia system, which is involved in the formation and retrieval of procedural (task-based) memory (Mastin).

Neurological or organic amnesia is amnesia caused by brain injury or damage. This can be the result of a stroke, brain inflammation resulting from a viral infection or an autoimmune reaction to cancer, oxygen deprivation to the brain, long-term alcohol abuse, tumors in certain areas of the brain, degenerative brain diseases such as Alzheimer’s, seizures, or certain medications, among others.

A simple head injury doesn’t usually cause severe amnesia; rather, the only memory loss is typically confusion and problems with remembering new information in the early stages of recovery (Mayo Clinic staff).  And despite the best efforts of hypnotists, there isn’t much scientific evidence for actively erasing selected memories.

So?

In reality, it takes a traumatic event to induce these dramatic forms of memory loss, and so thank goodness, aside from their prevalence in plot lines, the events depicted are actually highly unlikely.  This doesn’t detract from their appeal as a plot tool though. Hey, if reality were an issue for all movies, then the entertainment industry would be in some serious trouble.

 Written by Constance Kaita

Works Referenced

Images courtesy of comicvine.com, chud.com, fanpop.com, drross.org, its.sdsu.edu

Mastin, Luke. “Parts of the Brain.” Human-Memory.net. n.d. Web. 24 July 2013.

Mayo Clinic staff. “Amnesia: Causes.” MayoClinic.com. 11 October 2011. Web. 24 July 2013.

Nordqvist, Christian. “What Is Amnesia? What Causes Amnesia?” MedicalNewsToday.com. 14 July 2009. Web. 24 July 2013.

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