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Amnesia: Types, Tests, Diagnosis, Symptoms & Causes

By Olivia Guy-Evans, published March 18, 2022

by Saul Mcleod, PhD


What is amnesia?

Amnesia is a memory disorder whereby people find it difficult to remember past experiences, form new memories, or both. People with amnesia may find it hard to recall memories such as facts, information, and experiences, but they may also find difficulty in memorising new information and imagining the future. 

Being a little forgetful sometimes is different from amnesia. Similarly, mild memory loss as a natural part of ageing is considered normal.

Significant memory loss of the inability to form new memories, however, may indicate the presence of an amnesic disorder. Amnesia is also not the same as dementia or other degenerative disorders.

Dementia is a disease that causes degenerative memory loss, as well as those with the disease suffering from other cognitive issues that do not occur in those with amnesia. 

There is often a misconception with amnesia, especially present in movies, where people with amnesia are shown to forget their whole identity.

However, those with amnesia usually retain knowledge of their own identity, as well as having their motor skills intact. In many cases of amnesia, the memory loss is temporary and will return to normal after a period of time, but in others, the memory loss can be permanent. 

How does memory work?

There are three known types of memory:

  • Short-term memory (STM, also known as working memory) – these are thoughts that are temporary, usually lasting between 10-30 seconds. The frontal and parietal lobes of the brain are mostly responsible for STM.

  • Long-term memory (LTM) – thoughts that last beyond a minute or longer becomes an LTM. This is usually when the STM has been paid attention to so it can be processed deeper. The hippocampus and the temporal lobes are responsible for LTM. There are two types of LTM: implicit (procedural) and explicit (declarative). 

  • Sensory memory – this type of memory lasts for less than a second. This includes visual, auditory, and tactile sensory input that is briefly attended to and mostly forgotten or is passed on for further processing. 

There are four processes involved in memory: encoding, consolidation, storage, and retrieval. All of these processes determine whether something is remembered or forgotten:

  • Encoding – occurring in the prefrontal cortex, this is when the brain decodes new information. The information or experience is broken down into manageable parts for the rest of the brain to use.

  • Consolidation – occurring in the hippocampus, this is where the encoded information is linked to existing memories. This helps to determine where the new piece of information belongs and solidifies the memory.

    Consolidating memories organises everything in a way that will make it easier to recall in the future. 

  • Storage – taking place throughout the cortex, this is when the brain stores the information. The information that gets associated with existing memories get preserved and retained whereas the less important information gets edited out for the memory to stay focused on what is most important. 

  • Retrieval – occurring in the prefrontal cortex, hippocampus, and the cortex, this is when the brain reactivates the information for use in the future.

    During the retrieval process, the brain runs through encoding, consolidation, and storage of the memory repeatedly. With each run through, retrieval gets easier.

    The retrieval stage protects memories from being lost. The oldest and most retrieved memories are the most resilient. 

Symptoms

There are two main features of amnesia. Someone may either have difficulty learning new information following the onset of amnesia, or they may have difficulty remembering past events and information that was previously familiar to them. 

The symptoms of amnesia depend on the type of amnesia being experienced. Some of the common experiences of someone with amnesia are as follows:

  • Difficulty with recalling facts, events, places, and specific details

  • An impaired ability to learn new information 

  • Confusion 

  • An inability to recognise locations or faces 

  • Confabulation, in which the brain subconsciously invents false memories to fill in gaps in memory

  • Uncoordinated movements and tremors which may indicate neurological problems

  • Disorientation 

  • Partial, or total loss of memory

Most people with amnesia have problems with their short-term memory. This means that they cannot retain new information, with recent memories most likely to be lost.

In contrast, their long-term memories can remain intact, those being more deeply ingrained memories of the individual.

For instance, someone may be able to recall experiences from childhood or remember significant events from history, but not be able to know what month it is or what they last ate. 

Having amnesia does not mean that a person’s intelligence, general knowledge, attention, personality, sense of identity, or awareness is affected.

They will usually still retain their previously learnt skills such as understanding language, riding a bike, or playing an instrument. A person with amnesia may also understand that they are suffering from memory problems.

Types of amnesia

There are many different types of amnesia that a person may have. Below are some of the most common ones:

Anterograde amnesia

If someone has anterograde amnesia, it means that they cannot remember new information. The person is able to remember information and events that have happened before the onset of amnesia, but things that happened more recently and information that should be stored in STM disappears. 

The effect of this type of amnesia can be temporary such as when experiencing a blackout from consuming too much alcohol. It can also be permanent if the hippocampus becomes damaged, an area of the brain which plays a significant role in forming memories.

This type of amnesia is usually due to an error in the encoding or consolidating process of memory. When an event cannot be encoded or consolidated in the short-term, it makes it harder for the brain to store this information and process it for long-term retrieval in the future. 

Retrograde amnesia

In contrast to anterograde amnesia, someone with retrograde amnesia will be unable to remember old memories. In this instance, they cannot remember the events that occurred before the onset of their amnesia, but they can remember what happened afterwards. They will essentially lose their existing, previously made memories. 

This type of amnesia tends to affect the most recently formed memories first, so the events immediately leading up to the onset of amnesia will likely be forgotten first. Whereas older memories such as those from childhood are usually affected more slowly. 

Retrograde amnesia usually occurs due to a problem in the storage or retrieval stage of the memory process. Conditions such as dementia can cause gradual retrograde amnesia.

In rare cases, both retrograde and anterograde amnesia can occur together, so someone will lose their existing memories and be unable to form new memories. 

Transient global amnesia

Transient global amnesia is when someone has a temporary loss of all memory, and in severe cases, difficulty forming new memories.

This type of amnesia is very rare and is likely to occur in older adults with vascular disease. It is a sudden and temporary memory loss which can last between one to ten hours. 

When experiencing transient global amnesia, a person cannot make new memories or recall events during the period of amnesia. They can remember deeply ingrained information such as who they are and who their family is but are often unaware of where they are and what day, time, or month it is.

They can experience a lot of confusion and agitation that comes and goes repeatedly over the course of several hours. 

Traumatic amnesia

Someone experiencing traumatic amnesia suffers memory loss as a result of a hard blow to the head. They may have difficulty remembering events from minutes to hours ago, feel disorientated to time and where they are, and they may not understand what has happened to them. 

The person may experience a brief loss of consciousness or a coma prior to the amnesia. If someone experiences amnesia after trauma to the head, this may be an indicator that they are having a concussion. In some cases, amnesia is considered a normal part of the recovery processes following head trauma.

Amnesia from trauma to the head is usually temporary but how long it lasts depends on how severe the injury is. However, in some cases, traumatic amnesia can become permanent depending on the severity of the injury. 

Dissociative amnesia

Dissociative amnesia is a type of dissociative disorder, a condition which affects the consciousness, awareness, and perception of a person. In some instances, this can be limited to a specific area, but in more severe cases, a person may forget almost all their identity or take an entirely new identity. 

The onset of dissociative amnesia is usually sudden and may last for minutes, hours, or days, with rarer cases lasting for months of years. People usually develop this type of amnesia after experiencing a very stressful or traumatic experience as a way to cope with the situation.

Although the ability to remember usually returns, the memory of the shocking event which caused the amnesia may never come back completely. 

Infantile amnesia 

Infantile amnesia is when an adult has the inability to remember their first few years of life as a baby or a toddler. Most people cannot remember their first 3-5 years of life, making this a very common type of amnesia.

 

This inability to remember early life could be due to language not being fully developed yet, or some memory areas of the brain not being matured enough.  

What causes amnesia?

There are many causes of amnesia, but most fall into two categories: neurological and functional causes. 

Neurological 

Neurological amnesia is caused by various brain diseases, injury, infections, or other medical conditions. Other causes of this type of amnesia include:

  • Stroke 

  • Brain inflammation

  • Lack of oxygen to the brain e.g., from a heart attack or respiratory distress

  • Long-term alcohol abuse

  • Vascular disease which has been known to cause transient global amnesia

  • Tumors in the areas of the brain that control memory

  • Degenerative diseases such as Alzheimer’s disease

  • Seizure activity 

  • Certain medications such as benzodiazepines or other medications that have a sedative effect

Normal memory function involves many parts of the brain, so any disease or injury that affects the brain can also affect memory. Damage that occurs to the limbic system, an area of the brain that controls emotions and memories, specifically the hippocampus, may be a possible cause for amnesia developing in many people.

Anterograde amnesia typically results from damage to the prefrontal cortex or the hippocampus, whilst retrograde amnesia typically results from damage to the cortex but could involve the prefrontal cortex or hippocampus as well. 

Since the hippocampus plays a big role in forming memories, organising them, and retrieving them when needed, any damage to this area is detrimental as it limits these functions.

The cells of the hippocampus are also thought to be some of the most energy-hungry and fragile. Thus, they are most easily disrupted by low oxygen levels and other threats such as toxins. It is believed that if the hippocampus is damaged in both hemispheres of the brain, the person could develop complete anterograde amnesia. 

Electroconvulsive therapy (ECT) has also been shown to cause some amnesia as a side effect of the treatment. ECT is usually used as a treatment for depression or other conditions, where the person isn’t responding to other types of treatment.

This involves inducing seizures in specific brain regions for therapeutic effect. However, some people may experience some retrograde amnesia regarding the weeks of months before the treatment. They could also experience anterograde amnesia, usually resolving within a few weeks of treatment. 

Functional 

Functional causes of amnesia are usually related to psychiatric or emotional trauma. Functional amnesia also usually only causes retrograde amnesia, and doesn’t affect the ability to form new memories, although in severe cases, people with functional trauma can forget who they are. 

Dissociative amnesia stems from emotional shock or trauma such as experiencing or being the victim of a violent crime, or experiencing or being the victim of emotional, physical, or sexual abuse.

With this type of amnesia, the person’s mind rejects thoughts, feelings, or information that they are too overwhelmed to handle. They may briefly forget the trauma they went through, either briefly, or long-term. 

Any type of intolerable life situation can cause severe psychological stress and internal conflict that can lead to some degree of amnesia. This stress is more likely to disrupt personal and historical memories rather than interfering with making new memories. 

Diagnosis

To diagnose amnesia, doctors will usually complete a comprehensive evaluation, with the aim to rule out any other possible reasons for the memory loss.

The doctor will want to rule out conditions such as Alzheimer’s, other forms of dementia, depression, or a brain tumor. 

The evaluation may begin by completing a thorough medical history of the individual. As the person with suspected amnesia may not be able to provide all the necessary details, a family member or someone who knows the person well will generally take part in the interview too. T

he doctor will ask many questions to understand the memory loss. Some of the issues to address include:

  • Understanding the type of memory loss – including whether it is a recent problem or long-term.

  • When the memory problem started and how they may have progressed.

  • What could have been the possible cause for the memory loss e.g., head trauma.

  • A discussion of family medical history, especially of neurological diseases.

  • Whether the person uses drugs or drinks alcohol. 

  • Other signs and symptoms being experienced such as confusion, language problems, or personality changes. 

  • Whether the person has a history of headaches, seizures, or depression.

The examination should also include a physical exam to check the person’s reflexes, sensory function, balance, and any other aspects that may be necessary.

Cognitive tests will also be completed by the doctor to check the person’s thinking, judgement, short-term, and long-term memory. For instance, they may be asked about past events, given general knowledge questions, or asked to repeat a list of words.

This can all help to determine the extent of the memory loss and provide insights into what kind of treatment the person may need. 

The doctor may also arrange for diagnostic tests to investigate the memory loss further. This can include tests such as:

  • Imaging tests such a magnetic resonance imaging (MRI) and computerized tomography (CT) scans to check for brain damage or abnormalities. 

  • Blood tests to check for infection, nutritional deficiencies, or other issues.

  • An electroencephalogram (EEG) to check for the presence of seizure activity. 

Treatment

Treatment for amnesia depends on the type of amnesia being experienced and what caused the memory problems. With many types of amnesia, no treatment is necessary as it is likely that memory will return to normal in a short amount of time.

For instance, amnesia from mild head trauma may resolve itself within minutes or hours. Amnesia from a severe head injury may last a bit longer, for up to a week. In rarer cases, amnesia from a very severe head injury may last for months. 

For chemically induced amnesia from alcohol, this can be resolved through detoxication. Once this is out of the system, the memory problems of the person will probably subside.

If amnesia is caused as a side effect of medications such as benzodiazepines or other medications with a sedative effect, the medications could be gradually reduced, or the dosage can decrease, only with the advice given by a doctor.

It could be that a discussion of a person’s medicative treatment plan is required to weigh up the advantages and disadvantages of taking medication that is causing amnesia. 

Amnesia caused by neurological disease or infection will require treatment for the underlying medical cause of the amnesia. Once the medical issue is treated, this should also reduce the memory problems. Amnesia which is derived from dementia is often incurable.

However, a doctor may prescribe medications to support learning and memory for these individuals, such as donepezil, galantamine, or rivastigmine. 

As most functional amnesia results from emotional trauma, it may be useful to find a way to deal with the traumatic events in a safe way. The best therapy will usually depend on the individual and what caused the amnesia. Hypnosis can be an effective therapy for recalling memories that have been forgotten.

For many, the memory that has been forgotten may be too painful to rediscover, so instead it may be recommended to find a therapy that focuses on strategies to help make up for the memory problem and cope with additional negative thoughts surrounding the cause of the amnesia. 

People may wish to undergo any of the following therapies:

  • Cognitive behavioural therapy (CBT) 

  • Family therapy

  • Art or music therapy 

  • Meditation or mindfulness training 

  • Other types of psychotherapy 

Many people with amnesia may find that occupational therapy is the most useful for them if they have persistent memory loss. A person may work with an occupational therapist to learn new information to replace what may have been lost or use intact memories as a basis for taking in new information.

Memory training may also include different strategies for organising information so that it is easier to remember. The therapist can also teach the person how to use memory aids for organising information so it can be more effectively retrieved.

They may also suggest using digital aids such as smartphones, to help with daily tasks and set reminders about important events, or when to take their medication for instance. 

How can amnesia be prevented? 

In many cases, amnesia is not preventable. However, there are some ways to keep the mind active and the brain protected, especially when getting older in age, which could prevent age-related memory loss: 

Diet and physical exercise

Eating a diet with lots of nutrients and vitamins, as well as exercising regularly, could help to keep the brain healthy. Exercise, especially aerobic exercise, has been suggested to be linked to improved memory and thinking skills.

This may be due to more blood being pumped around regions of the brain that specifically improve memory and mental sharpness (Guadagni et al., 2020).

Aside from food, staying hydrated is important as it is suggested that even mild dehydration can adversely affect brain functioning and cause a cognitive decline (Pross, 2017).

Staying mentally active

Whilst it is important to keep physically active, keeping the mind active may also help to prevent memory loss.

This can include reading books or playing mind-stimulating games. Activities which involve mental effort like problem-solving or using imagination, can help stimulate the mind. 

Quality sleep 

It has been suggested that a lack of sleep can impair a person’s ability to focus and learn efficiently and that sleep is necessary to consolidate a memory so that it can be recalled in the future (Marks, 2021).

Therefore, sleep may be crucial for the brain’s ability to learn and remember, so ensuring a regular sleep pattern and getting plenty of sleep may help to prevent memory loss in the future.

Managing stressors

Stress can affect how memories are formed such as finding it more difficult to create short-term memories and turning those into long-term memories. Also, during periods of stress, one is less likely to accurately remember details of the event later.

Therefore, managing stressors in life could help to prevent problems with memory. This can include good sleep and physical activity, as mentioned above, but can also include breathing exercises, mindfulness, or cutting unnecessary known stressors from life.

Protecting the head

Since damage to the brain can cause amnesia, making sure to protect the head wherever possible can help prevent amnesia associated with brain trauma. Some preventions for head trauma include:

  • Wearing protective headgear when cycling and motorcycling. 

  • Wearing a seatbelt in the car.

  • Avoiding excessive alcohol drinking so that balance is less likely to be lost. 

  • Getting eye check-ups annually to help prevent dizziness that can result in falls. 

  • Ask the doctor about any prescribed medications and whether they may cause dizziness.

Fact Checking
Simply Psychology content is rigorously reviewed by a team of qualified and experienced fact checkers. Fact checkers review articles for factual accuracy, relevance, and timeliness. We rely on the most current and reputable sources, which are cited in the text and listed at the bottom of each article. Content is fact checked after it has been edited and before publication.

About the Author

Olivia Guy-Evans obtained her undergraduate degree in Educational Psychology at Edge Hill University in 2015. She then received her master’s degree in Psychology of Education from the University of Bristol in 2019. Olivia has been working as a support worker for adults with learning disabilities in Bristol for the last four years.

How to reference this article:

Guy-Evans, O. (2022, March 18. Amnesia: Types, Tests, Diagnosis, Symptoms & Causes. Simply Psychology. www.simplypsychology.org/amnesia.html

APA Style References

Guadagni, V., Drogos, L. L., Tyndall, A. V., Davenport, M. H., Anderson, T. J., Eskes, G. A., Longman, R. S., Hill, M. D. & Poulin, M. J. (2020). Aerobic exercise improves cognition and cerebrovascular regulation in older adults. Neurology, 94(21), e2245-e2257.

Pross, N. (2017). Effects of dehydration on brain functioning: a life-span perspective. Annals of Nutrition and Metabolism, 70(Suppl. 1), 30-36.

Brazier, Y. (2017, December 13). What is amnesia and how is it treated? Medical News Today. https://www.medicalnewstoday.com/articles/9673#types 

Mayo Clinic Staff. (2020, September 15). Amnesia. Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/amnesia/symptoms-causes/syc-20353360 

Marks, H. (2021, August 27). Sleep Deprivation and Memory Loss. WebMD. https://www.webmd.com/sleep-disorders/sleep-deprivation-effects-on-memory

Jividen, S. (2021, October 18). All About the Different Types of Amnesia. Very Well Health. https://www.verywellhealth.com/amnesia-types-5203061 

Barclay, R. & Goldman, L. (2021, November 18). Understanding Amnesia. Healthline. https://www.healthline.com/health/amnesia

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