Two Forms Of Amnesia

Memory loss is one of the most well-known memory disorders. These are significant shortcomings in the encryption, storage and retrieval of information. However, the psychological memory processes are extremely complex and multifaceted. There are multiple types of amnesia and therefore it can be difficult to explain this problem in detail.

It’s also why people with amnesia have been such a valuable resource for gaining a deeper understanding of how memory works. Research into memory disorders helps us to understand its structure and functioning.

These studies mainly focus on forms of amnesia in which someone’s episodic memory has been damaged and no longer works properly.

So if we want to investigate amnesia and episodic memory, we need to focus on the effect that damage has. In that case we can speak of  two basic forms of amnesia.

The first form is retrograde amnesia : when a person forgets things that happened to him before his illness or accident. And the second form is anterograde amnesia : when a person can no longer make new memories.

In this article, we’ll take a closer look at both types of amnesia.

Two forms of amnesia

retrograde amnesia

Retrograde amnesia is characterized by an inability to access memories from before the memory was damaged. The time period it affects varies a lot. Some people just forget for a few days and others forget for a lifetime.

It is also important to remember that someone with this type of amnesia can still make new memories. He can also use other parts of his memory, such as his implicit memory and his procedural memory.

The cause of this condition is usually physical. In other words, it occurs when there is some kind of brain damage. This usually involves damage in or around the hippocampus, basal ganglia or the interbrain.

However, there are also cases where retrograde amnesia occurs without any kind of injury. This is then called dissociative amnesia.

Clive Wearing was one of the most studied patients with severe memory impairment. Clive couldn’t remember anything that happened to him before his accident in 1985. An accident that completely destroyed his hippocampus and severely damaged his temporal lobes.

Clive also had anterograde amnesia. So he couldn’t make new memories either. Because of this, he was constantly stuck in the present.

Anterograde amnesia

Anterograde is basically the opposite of retrograde amnesia. It means  that after a certain injury you can no longer make new memories. Any information you stored before the injury will therefore still be there.

Like retrograde amnesia, anterograde amnesia is the result of a physical injury. However, the brain regions affected in this case are the hypothalamus and temporal lobes.

A unique aspect of this condition is that it affects only explicit memory. This means that although a person can no longer make new memories, he can still learn new skills, whether they are procedural or implicit.

For example, if someone with anterograde amnesia plays the piano every day, they will get better at it over time. Unfortunately, however, he will not be able to remember playing the piano, because every day is like his first day for him.

One of the most famous cases of anterograde amnesia was the patient HM (which stands for Henry Molaison). He had to undergo surgery to deal with his seizures. However, during the surgery, the doctors took too much away from his hypothalamus. After the operation he had no more epileptic seizures, but unfortunately he had serious memory problems.

HM couldn’t store any new memories. However, its procedural and executive memory functions still worked. He was always clear and coherent during a conversation. It didn’t seem like there was anything wrong with him. However, if the conversation was briefly interrupted and then brought back to it, he didn’t remember anything.

Finally

We mentioned earlier that these two types of amnesia are independent of each other. In other words, you can suffer from one form without also suffering from the other. However, it is important to remember that amnesia are much more complicated than that.

Normally, these types of injuries affect more than one area of ​​the brain, leading to a mixed type of memory loss. Yet it is also interesting to study ‘pure’ forms of amnesia and to learn more about how memory works.