How Many Types Of Amnesia Are There?

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There are many types of amnesia. The most common are retrograde and anterograde amnesia, but there are also other types, such as transient global amnesia, infantile amnesia, posthypnotic amnesia, fugue state, and more.

As a fiction writer that is particularly fond of tragic themes, I love toying with the concept of amnesia. It has the right amount of tragedy in it, but also lends the flexibility of playing around. It also allows me to block out events, and sometimes even incorporate an alternate version of a storyline in the same story!

However, this often makes me wonder about the different ways that amnesia can affect the brain. What are the different ways that our memory can be lost, and is it always permanently lost or more often only temporarily lost?

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Amnesia is the loss of memory, or the inability to retrieve it. Any problem in the normal process of the formation of new memories, their conversion from short-term to long-term storage, or their retrieval can result in such memory loss. It may or may not be a permanent state, depending on the cause.

The most common forms of amnesia depicted in most works of fiction are retrograde and anterograde amnesia. However, there are many other forms too, which may not be as popular or common. However, a brief understanding of semantic and procedural memory will be helpful in understanding these various forms.

Also Read: Why Don’t Patients Of Memory Loss Forget Their Language?

Types Of Amnesia

Amnesia can occur due to physical trauma to the head, psychological or emotional trauma, anoxia, substance abuse or diseases like Alzheimer’s. Apart from this, certain therapies, such as electroconvulsive therapy, can also cause some forms of amnesia.

Retrograde Amnesia

One of the most common forms depicted in movies, this variety involves the loss of memory of past events. It occurs due to damage to the brain, but not the hippocampus, as that part of the brain is responsible for forming new memories, or it can be caused by psychological trauma or stress. It is usually temporary, but may be permanent in certain cases. In extreme cases, however, a person may even forget who they are.

The affected person can usually remember older memories, more so than newer ones, as older memories are ingrained in the brain over time.

Anterograde Amnesia

The other most commonly depicted form of amnesia is where a person is unable to form new memories. This is caused by damage to the hippocampus. The person can remember all their past memories, but is unable to form new ones. However, by repeating actions over and over again, they can become remembered as procedural memory.

However, retrograde and anterograde amnesia can also occur at the same time!

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Transient Global Amnesia (TGA)

This is a very rare form of amnesia, although is it portrayed relatively often in works of fiction. In this type, the affected person experiences episodes where they forget where they are and how and why they got there. They may be unable to register new details, or even be blank when asked to remember things that occurred days, weeks or even years earlier. However, this is usually temporary and rare, and the person can still remember who they are and recognize the people around them. These episodes don’t usually reoccur.

While these 3 are the more commonly known varieties, there are several other types of amnesia.

Infantile Amnesia

This is the common inability to remember memories up until the age of 4-5. A modern theory states that this is related to language development, i.e., it is hard to remember any events that occurred before we learned to talk. However, this doesn’t apply to procedural memories, such as walking, etc.

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Posthypnotic Amnesia

In this type, due to suggestive input during a hypnotic state, a person fails to recollect memories from the hypnosis period, or even from before that.

Fugue State

This is an extremely rare psychiatric disorder, and is classified as a type of dissociative amnesia. In this situation, a person loses parts of their memory like identity, personality, etc., which are related to their existence as an individual. Although this is a reversible type of amnesia, it sometimes results in a person acquiring a new personality.

Fugue State leads to confusion about personality. (Photo Credit : Pixel)

There are other types too, wherein a person can remember some information, but not its origin or source, i.e., how they became privy to that information. In some cases, a person may try to block out a specific incident or memory, which is sometimes a part of PTSD (post-traumatic stress disorder). In this case, there isn’t necessarily a physical injury blocking the memory; rather, the person subconsciously blocks out the memory instead of dealing with it.

As fancy and intriguing as it sounds, amnesia is quite tragic. It would be extremely disorienting to wake up one day with a chunk of your memory gone, or with the inability to form new ones. To live and not remember or register can be the ultimate curse.

That being said, the inner writer in me can’t ignore the fact that this is a whole new playing field for tragic themes. However, it’s best left to the pages of fiction novels!

Also Read: Childhood Amnesia: Why Don’t We Remember Things From Our Infant Years?

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References (click to expand)
  1. Amnesia - Wikipedia. Wikipedia
  2. Amnesia - Better Health Channel.
  3. How are memories formed? - Queensland Brain Institute. The Queensland Brain Institute
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About the Author

Mahak Jalan has a BSc degree in Zoology from Mumbai University in India. She loves animals, books and biology. She has a general assumption that everyone shares her enthusiasm about the human body! An introvert by nature, she finds solace in music and writing.