A memory disorder is any health condition that impairs the memory. This can be the result of a number of factors and can be temporary, recurring, or permanent in nature. It can also affect all memory or only certain aspects of memory. Some forms of memory loss are treatable or curable, while others are irreversible.
In human beings, most memory functions pass through the hippocampus, a portion of the brain located in the cerebral cortex, whose primary purpose seems to be sorting memory. In many patients, a memory disorder is associated with disease, injury, or malfunction in this part of the brain. Different types of memory, however, are actually stored in different parts of the brain, including the frontal and temporal lobes, the amygdala, and the cerebellum. Damage to any of these parts of the brain can result in memory loss.
Certain diseases can result in a memory disorder as well. These include diseases related specifically to memory, such as dementia and Alzheimer's disease. Other diseases, however, can also affect memory. These include alcoholism and syphilis.
Long-term use of certain drugs, including both prescription and illicit drugs, can result in a memory disorder. Another potential cause is emotional trauma. Additionally, lack of oxygen, which can be caused by breathing disorders such as asthma or by traumas such as drowning, can also result in memory loss, as can injuries sustained in car crashes, falls, and other traumas that result in head injuries.
The type of memory loss sustained has to do largely with the nature of the injury or illness and the area of the brain it affects. One portion of memory may be irretrievable while another may be completely unaffected. For example, an Alzheimer's patient may, especially in the early stages, remember how to do things such as ride a bike and have very clear memories of events in the distant past, but be unable to recall what he ate for lunch or, indeed, if he even ate lunch. Another type of injury might leave a patient unable to accomplish functions such as walking or eating, even though he has retained all of the factual knowledge in his possession prior to the injury.
Depending on the circumstances, a memory disorder can cause temporary or permanent memory loss. Memory loss may also be incomplete, meaning that the patient remembers some things, either immediately or after a period of time, but never regains other memories. Memory loss may be intermittent as well, meaning that the affected person remembers things some of the time, but not at other times.