How does amnesia occur

Amnesia refers to a large-scale loss of memories that should not have been forgotten. These may include important milestones in life, memorable events, key people in our lives, and vital facts we have been told or taught. People with amnesia also find it hard to remember the past, memorize new information, and imagine the future. This is because we construct future scenarios on the basis of our recollections of past experiences.

Our ability to recollect events and experiences involves a variety of complex brain processes. Most people with amnesia are usually lucid and have a sense of self. However, they may experience severe difficulties in learning new information, struggle to recall memories of past experiences, or both. Amnesia is different from dementia. Any disease or injury that affects the brain can interfere with memory. Memory function engages many different parts of the brain simultaneously.

Damage to brain structures that form the limbic system, such as the hippocampus and thalamus, can lead to amnesia — the limbic system controls our emotions and memories. Any intolerable life situation that causes severe psychological stress and internal conflict can lead to some degree of amnesia. Symptoms of amnesia The symptoms of amnesia depend on the cause, but generally include: Memory loss Confusion Inability to recognise familiar faces or places Once the person recovers, they typically have no memory of their amnesia episode.

Causes of amnesia Memory loss can be caused by a wide range of conditions, including: Head injury Severe illness High fever Seizures Emotional shock or hysteria Alcohol-related brain damage Certain drugs, such as barbiturates or heroin General anaesthetics Electroconvulsive therapy Stroke Transient ischaemic attack a 'mini stroke' Alzheimer's disease Brain surgery.

Memory is mysterious The way the brain codes and stores information remains a mystery. Current and often conflicting theories include: Widespread distribution of memories across the outermost layer of the brain cortex Widespread distribution of memories, with certain structures such as the hippocampus playing important roles Localised memory areas in certain structures of the brain only Memory storage in brain molecules Memory storage in clusters of nerve cells neurones.

Different types of memory It seems that the brain has a number of different memory forms, including: Short term - new information is stored for a brief time. If the information isn't further processed, it will soon be forgotten. Long term - information from the short term memory is shifted to the long term memory. Declarative - conscious memories of information and events.

Non-declarative - once learned, habits such as driving a car are ingrained and automatic. The severity varies The severity of amnesia depends on the cause. Diagnosis of amnesia Diagnosing the cause of amnesia involves a range of tests, including: Medical history General examination Tests for short and long term memory recall Other tests related to thought processing Head x-ray Blood tests Computed tomography CT scan Cerebral angiography scans taken after a special dye is injected.

Treatment for amnesia Treatment depends on the cause. Where to get help Your doctor Always call an ambulance in an emergency, Tel. Give feedback about this page. Was this page helpful? Philadelphia, PA: Elsevier; chap 5. Editorial team. Memory loss. In severe cases, such memory impairment may interfere with daily living activities.

Memory loss may result from a new injury to the brain, which is caused by or is present after: Brain tumor Cancer treatment, such as brain radiation , bone marrow transplant , or chemotherapy Concussion or head trauma Not enough oxygen getting to the brain when your heart or breathing is stopped for too long Severe brain infection or infection around brain Major surgery or severe illness, including brain surgery Transient global amnesia sudden, temporary loss of memory of unclear cause Transient ischemic attack TIA or stroke Hydrocephalus fluid collection in the brain Multiple sclerosis Dementia Sometimes, memory loss occurs with mental health problems, such as: After a major, traumatic or stressful event Bipolar disorder Depression or other mental health disorders, such as schizophrenia Memory loss may be a sign of dementia.

A person with memory loss needs a lot of support. It helps to show the person familiar objects, music, or and photos or play familiar music. Write down when the person should take any medicine or do other important tasks. It is important to write it down. If a person needs help with everyday tasks, or if safety or nutrition is a concern, you may want to consider extended-care facilities, such as a nursing home.

The most famous patient with amnesia is known by his initials: H. Scientists use initials to protect the identity of patients when they write about them in scientific articles. Henry Molaison was born in Molaison had seizures when he was a child, which means that his brain was not working normally. These seizures caused Mr. Molaison to have a very difficult life. To stop the seizures, a brain surgeon named Dr. William Scoville removed both of Mr.

Because this happened a long time ago, the surgeon was not completely sure what would happen. Scientists did not know what the hippocampus was important for yet, and Dr. Scoville thought he could help Mr. A good thing that happened because of the surgery was that Mr. But, unfortunately, removing both of Mr.

He had amnesia. Amnesia made lots of things difficult for Mr. But, Mr. Molaison also helped scientists learn a lot about the brain and about what the hippocampus does [ 2 ]. The scientists who worked with Mr. Molaison were the first to discover that the hippocampus was important for memory. While many different scientists worked with Mr. Molaison, two of the most famous were Brenda Milner and Suzanne Corkin. Before Mr. After Mr. Another thing that Mr. After his surgery, Mr.

Molaison had bad memory problems and was not able to form new memories for facts and events. You might think that Mr. Molaison would have many other problems besides this memory impairment, but this was not the case. After the surgery, Mr. Molaison was just as intelligent and able to problem-solve as he was before his surgery.

He seemed to have normal thinking abilities and normal language ability. Molaison also had the same personality as he did before his surgery. People who have amnesia have a very hard time learning and remembering new information. In real-life amnesia, it is not common for people to forget things about themselves or to forget things that have happened to them in the past. In general, people with amnesia have a hard time learning new information [ 3 ].

They have a hard time learning new things after they damage the hippocampus. This kind of amnesia has a specific name: anterograde amnesia Figure 2. The things that they learned before they hurt the hippocampus are not usually hard for them to remember.