What is a memory disorder?
What is amnesia?
In the movies, people with amnesia forget who they are. Isn't that a memory disorder?
Can people with amnesia learn new things?
What parts of the brain are associated with memory problems?
What causes amnesia?
How do you find out if you have a memory disorder?
What can you do to help your memory if you have amnesia?
Can you improve normal memory?
How does the brain form memories and where are they stored?
How can I get involved in memory research?

What is a memory disorder?
A memory disorder is a problem storing and/or retrieving memories. It can be mild or severe, and is often the result of a disease or injury that affects the brain. One form of memory disorder is anterograde amnesia, in which an individual may remember events from the distant past, but will be unable to remember what happened a few minutes or hours ago. Everyone forgets some information from time to time, but an individual with anterograde amnesia forgets information so frequently that it interferes with the ability to carry out the activities of daily life.


What is amnesia?
The most common form of memory disorder involves difficulties in forming new memories. A severe example is anterograde amnesia, a rare condition which can result from brain injury or disease. Someone with anterograde amnesia will generally have good memory for the past, up until the time of the brain injury, but will have extreme difficulty remembering anything that has happened since then. Such a person may not be able to remember what he had for breakfast, what year it is, what he did yesterday, and so on. However, the person's personality, intelligence and judgement may be unaffected. This type of memory disorder is devastating for patients and for their families. Often, individuals with anterograde amnesia have trouble holding a job -- not because they are not capable of doing the work, but simply because they have trouble remembering from minute to minute what it is they are supposed to be doing. Currently, there is no known way to repair the brain damage which causes anterograde amnesia. However, the use of memory aids (such as detailed daily schedules) and other methods can help these people cope with their memory disorder.

Another severe type of memory disorder is called retrograde amnesia. Retrograde amnesia is also usually caused by brain injury or disease. In this condition, individuals have trouble remembering events in their life that occurred prior to the brain injury. These people do not lose all their memories. Usually, the memory loss is worst for events just before the injury; events from long ago are more likely to be safe. For example, if a man developed retrograde amnesia in middle age, he might have excellent memory for his childhood, nearly complete memories of young adulthood, and progressively less memory for the years leading up to his brain injury. There have been reports of persons with memory disorders being unable to remember that they are married, if the marriage took place shortly before the brain injury that caused the amnesia. Currently, there is no known way to restore memories which have been lost through retrograde amnesia.

Usually, when a person has a brain injury resulting in a memory disorder, there is some degree of both anterograde and retrograde amnesia. Often, the anterograde amnesia is more severe and more difficult to deal with. For this reason, scientists and doctors often just use the word "amnesia" to refer to a general condition involving severe anterograde amnesia and some degree of retrograde amnesia.

In the movies, people with amnesia forget who they are. Isn't that a memory disorder?
This kind of memory loss is often called a "fugue state". People who enter fugue state may completely forget their identities and personal histories. Fugue state is usually the result of psychological trauma (for example, witnessing a violent crime) and often resolves itself with time or with psychotherapy. Thus, it is a different kind of syndrome from memory disorders such as anterograde amnesia, which typically result from brain injury and which are typically permanent conditions.


Can people with amnesia learn new things?
YES! You can still learn things even if you have severe amnesia. Scientists believe that there are different forms of memories that depend on different brain regions. One type of memory involves remembering individual facts or events (such as what you did yesterday, or what country Paris is in). This kind of memory is often called declarative memory, because it is easy to state or "declare" the content of the memory.

But there are other kinds of memory, too, such as memory for habits or skills. An example is learning to ride a bike or to tie a shoelace. Unlike declarative memory, it is very difficult to state or declare the rules for how to tie a shoelace, even though you may understand the procedure very well. For this reason, this kind of memory is sometimes called procedural memory.

Typically, individuals with severe anterograde amnesia are greatly impaired in their ability to acquire new declarative memories, but they may not be impaired at acquiring new procedural memories. Thus, a person with anterograde amnesia who has never ridden a bike can be taught how. The next day, when that person sees the bike, he may have no memory of ever seeing it before or of learning how to ride -- but if he tries, he may do very well. Many kinds of skills can be taught using procedural memory, including some aspects of learning to program a computer. This suggests the exciting possibility that individuals with anterograde amnesia may benefit from rehabilitation which takes advantage of their surviving procedural memory abilities.

What parts of the brain are associated with memory problems?
Many areas of the brain are involved in memory, and so many kinds of damage can cause some kind of memory disorder. However, three particular areas are especially implicated in anterograde amnesia. One is the hippocampus and associated structures in the medial temporal lobes. Another is the diencephalic region, which includes the thalamus. A third is the basal forebrain region. Each of these regions plays a different role in memory, and so the deficits which follow injury will differ depending on where the injury is located. However, damage to any of these areas can result in anterograde amnesia.


What causes amnesia?
Although severe anterograde amnesia is relatively rare, the causes are extremely diverse. A few of the most common are:

• stroke or aneurysm (especially of the anterior communicating artery or posterior communicating artery)
• traumatic head injury or brain tumor which damages the hippocampus or other important memory areas
• encephalitis (particularly herpes encephalitis)
• hydrocephalus
• epilepsy (in particular, uncontrolled seizures for a long time)
• hypoxia or anoxia (brief reduction or loss of oxygen to the brain); this can occur during cardiac arrest, carbon monoxide poisoning, near-drowning and near-suffocation
• Korsakoff's disease (a syndrome caused by alcohol abuse combined with malnutrition over a period of years)

In each of these cases, the damage is usually limited to a particular period in time, and so the memory deficit may remain stable thereafter.

Another cause of amnesia is diseases such as Alzheimer's disease and other dementias. These diseases are usually progressive, meaning that the brain injury gets worse with time and so does the memory deficit.

How do you find out if you have a memory disorder?
If you have experienced a brain injury then you have probably seen a neurologist and possibly a neuropsychologist. Both of these professionals have the means to examine your memory to determine whether or not it is impaired. A neuropsychologist may use a battery of standardized behavioral tests to examine memory, as well as other cognitive (thinking) abilities. A neurologist may administer other behavioral tests and may suggest a brain scan such as a CT, MRI or SPECT scan. For more information about neuropsychological tests and what they measure, you can contact your neuropsychologist. Please also see our section on references, where we have a list of books that may be informative.

Sometimes, people develop memory disorders even though they have not been treated for a brain injury. If you feel that your memory is not working as efficiently as it should be, you may wish to talk to your doctor, and discuss the possibility of further testing. In many cases, memory can be affected by conditions like depression, infection and hormonal imbalances which can be treated.

It is also important to remember that memory does degrade as we get older, and that some degree of decline is "normal". If your memory doesn't seem as sharp as it did thirty years ago, this is not necessarily a sign of disease. One rule of thumb is to talk to friends or family members in your age group. If your memory seems worse than theirs, or if family members have noticed problems, you may want to talk to your doctor.

What can you do to help your memory if you have amnesia?
Unfortunately, right now we have no way to cure anterograde amnesia, although there are cognitive rehabilitation techniques which teach individuals how to cope as best they can with the demands of daily life. Some of these techniques take advantage of the individuals' remaining abilities, such as procedural memory. However, depending on the severity of the memory deficit, the benefits of rehabilitation may be limited. Rehabilitation is usually most successful in people whose memory deficit is mild, and who do not have other kinds of impairments. It is less likely to be successful in people whose memory deficit is severe and who have additional problems such as attentional impairments or cognitive impairments.

Some common rehabilitation techniques include using a memory notebook (write down daily events, plans for the week, etc. and reference it regularly), putting notes around the house that are reminders of important events or tasks, and lastly, repetition. For certain types of memory deficits, repetition of information is beneficial. It may also help to learn how to associate new information with old memories: in effect, "attaching" the new information to old information that is already well-stored in memory.

In addition to the rehabilitation strategies, there are new prescription drugs available for the treatment of the symptoms of Alzheimer's disease. These drugs may prove to be helpful in treating anterograde amnesia as well. You may want to talk to your doctor about them.

For more information on cognitive rehabilitation or the new prescriptions on the market you can contact your neurologist or neuropsychologist.

Can you improve normal memory?
There isn't a simple yes or no answer to this question. What we do know is that keeping your mind active by doing things that are mentally challenging (such as doing crossword puzzles or reading books), is good for your brain. Such "mental exercise" keeps brain cells (called neurons) active. Physical exercise is good for your brain, too. It not only keeps the neurons in the motor portions of your brain busy but it also helps to improve the blood flow to all of the parts of the brain. This is important in keeping the brain cells adequately supplied with nutrition.


How does the brain form memories and where are they stored?
We do not know for sure how the brain forms a memory. We do know that there are certain measurable changes in the brain that occur when something is learned. Some of these take the form of changes in connections between brain cells (neurons), making it easier for them to communicate with each other.

We also do not know for sure where memories are stored. However, different parts of the brain seem to specialize in different forms of information: visual information is processed near the back of the brain, in the visual cortex, sensory information is processed in the sensory cortex, near the top of the head, and so on. However, in general, memories appears to be spread or "distributed" throughout large regions of the brain, rather than localized in any one place.