What is amnesia?

What is amnesia?

Simply, amnesia is memory loss triggered by disease, brain damage or psychological trauma. The severity of the memory loss entirely depends on the cause and the seriousness of the trigger.

In many instances, amnesia is a temporary condition, lasting anything from a few seconds to a number of months, depending on the type of amnesia suffered by the patient.

Being somewhat forgetful is completely different from amnesia, by the way. Forgetting little details and aspects of daily life is to be expected – amnesia refers to the large-scale loss of memories that shouldn’t be discarded – such as key life events, people and their personal history.

Depending on what kind of amnesia it is, the patient may forget their memories pre-amnesia, or they may lose the ability to form new ones. In some rare cases, patients can suffer from both.car_accident_amnesia

What different types of amnesia are there?

There are two main types of amnesia: anterograde and retrograde.

Anterograde amnesia:

Anterograde amnesia is when a patient can no longer create new memories. In other words, anything that happens after their trigger will not be recalled, due to a failure to commit short-term memories into long-term ones. In this instance, memories stored before amnesia struck would remain fully accessible. Anterograde amnesia is usually caused by brain damage – from a blow to the head, for example.

Retrograde amnesia:

Retrograde is kind of the opposite: memories from before the trigger are lost, but new memories are still able to be formed. This is less common.

Cruelly, having anterograde amnesia is no guarantee of a patient being free of retrograde amnesia, or vice versa. In other words, it’s possible (though rare) for a patient to lose all of their pre-amnesia memories, and yet be unable to forge new ones to replace them. This was the case with Clive Wearing, an accomplished British musician who was the subject of a number of documentaries such as the one below.

On top of these main two, there are various subsets of amnesia, which are considerably less common:

Psychogenic amnesia

Also known as “functional” or “dissociative” amnesia, this kind of memory loss causes the patient to forget the event that triggered their amnesia. Anything from child abuse to traumatic war incidents can cause this.

Traumatic amnesia

This kind of amnesia is caused by a very hard impact to the head, such as a car accident. This would usually be accompanied by a loss of consciousness, but the good news is that this kind of amnesia is usually temporary.

Wernicke-Korsakoff psychosis

The kind of memory loss caused either by extended alcohol abuse or by malnutrition. It gets worse over time, and is often accompanied by neurological problems and the loss of feeling in the extremities.

Transient global amnesia

All memory is temporarily lost, and new ones can’t be formed. Extremely rare, most common in older patients and usually found in tandem with a vascular disease. It is also defined by lasting for only a very short period of time.

Fugue amnesia

Patients suddenly forget both their past and their identity – right down to not recognising their reflection in the mirror. Typically, this would be triggered by a life event that the patient couldn’t adequately cope with, and the sufferer will find their memories restoring over the space of a few days.

Blackout amnesia

The short-term amnesia that many students will be familiar with: excessive drinking leading to “black spots” of a particular night of excess.amnesia_drink

What are the causes of amnesia?

Depending on the type, there are various possible causes.

Certain kinds of amnesia are driven by narcotics of some kind – either alcohol or something harder. In short, intoxicants impair the formation of new memories, so they aren’t stored.

Dissociative amnesia – that is to say when memory loss seems to be triggered by a traumatic event – seems to be some kind of defence mechanism, but could also be seen as a symptom of post-traumatic stress.

Post-traumatic amnesias are usually caused by some kind of head injury. This can trigger either anterograde or retrograde amnesia, or both simultaneously, and the severity seems to relate to the seriousness of the impact.

On top of this, retrograde amnesia can also be triggered by various other factors including strokes, tumours, hypoxia, encephalitis and alcoholism.

What is the treatment for amnesia?

That very much depends on the type of amnesia, and the severity. Certain kinds will “fix themselves” after a time – perhaps in minutes, perhaps in months.

Others will not, of course. If a brain cell is dead, it cannot be replaced – but in cases where the illness is temporary, certain guidance is advised for aiding the patient to return to normal. In the case of retrograde amnesia, psychotherapy is sometimes recommended, along with ensuring the surroundings of the patient have plenty of cues to remind them of the life they’ve forgotten – photographs, familiar objects… even smells and music to trigger their previous memories.

Those unable to create new memories require high levels of supervision, or reminders to ensure they go about their routine without memory triggers. Technology can help here, too.

How has amnesia been treated in popular culture?

As a narrative device, retrograde amnesia has been extremely helpful in literature, cinema, television and gaming, as it creates a sense of intrigue and means that – to a certain extent – the viewer/reader/player is in exactly the same place as the protagonist, knowing nothing about the character’s past.

How accurately amnesia has been portrayed is another matter entirely. Ironically, perhaps the most accurate was Walter White in Breaking Bad – ironic because he was only pretending to enter a fugue state in order to avoid having to come clean about his drug kingpin lifestyle to his long-suffering wife, Skyler. These things do happen, but Skyler was right to be sceptical, as they’re extremely rare, and in the case of Walt, extremely convenient.

In television and cinema, it’s a handy narrative device, but usually a temporary one – the character tends to regain their memory fully by the end of the episode. One common mechanism for this is a second bump on the head “undoing” the amnesia: this is another science myth, as explained by the BBC here – although those with traumatic brain injuries are more likely to receive a second blow to the head, it won’t make them better, no matter what the big screen has taught us.

Interestingly, almost all television and film uses retrograde amnesia for its inspiration, with the anterograde variety barely mentioned. The one big exception is Memento – the main character has to keep notes and reminders around the house and on his body in order to keep understanding the world around him.

Read this next: what is sleep paralysis?

Images: Radiobread, Tommy and Georgi, and Allan Afijo used under Creative Commons.

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