Memory

Memory (psychology), processes by which people and other organisms encode, store, and retrieve information. Encoding refers to the initial perception and registration of information. Storage is the retention of encoded information over time. Retrieval refers to the processes involved in using stored information. Whenever people successfully recall a prior experience, they must have encoded, stored, and retrieved information about the experience. Conversely, memory failure—for example, forgetting an important fact—reflects a breakdown in one of these stages of memory.

TYPES OF MEMORY

Although the English language uses a single word for memory, there are actually many different kinds. Most theoretical models of memory distinguish three main systems or types: sensory memory, short-term or working memory, and long-term memory. Within each of these categories are further divisions.


Sensory Memory -> Sensory memory refers to the initial, momentary recording of information in our sensory systems. When sensations strike our eyes, they linger briefly in the visual system. This kind of sensory memory is called iconic memory and refers to the usually brief visual persistence of information as it is being interpreted by the visual system. Echoic memory is the name applied to the same phenomenon in the auditory domain: the brief mental echo that persists after information has been heard. Similar systems are assumed to exist for other sensory systems (touch, taste, and smell), although researchers have studied these senses less thoroughly.

Sensory memory systems typically function outside of awareness and store information for only a very short time. Iconic memory seems to last less than a second. Echoic memory probably lasts a bit longer; estimates range up to three or four seconds. Usually sensory information coming in next replaces the old information. For example, when we move our eyes, new visual input masks or erases the first image. The information in sensory memory vanishes unless it captures our attention and enters working memory.

Short-Term or Working Memory -> Psychologists originally used the term short-term memory to refer to the ability to hold information in mind over a brief period of time. As conceptions of short-term memory expanded to include more than just the brief storage of information, psychologists created new terminology. The term working memory is now commonly used to refer to a broader system that both stores information briefly and allows manipulation and use of the stored information.

We can keep information circulating in working memory by rehearsing it. For example, suppose you look up a telephone number in a directory. You can hold the number in memory almost indefinitely by saying it over and over to yourself. But if something distracts you for a moment, you may quickly lose it and have to look it up again. Forgetting can occur rapidly from working memory.

Long-Term Memory ->
The term long-term memory is somewhat of a catch-all phrase because it can refer to facts learned a few minutes ago, personal memories many decades old, or skills learned with practice. Generally, however, long-term memory describes a system in the brain that can store vast amounts of information on a relatively enduring basis. When you play soccer, remember what you had for lunch yesterday, recall your first birthday party, play a trivia game, or sing along to a favorite song, you draw on information and skills stored in long-term memory.

There seems to be no finite capacity to long-term memory. People can learn and retain new facts and skills throughout their lives. Although older adults may show a decline in certain capacities—for example, recalling recent events—they can still profit from experience even in old age. For example, vocabulary increases over the entire life span. The brain remains plastic and capable of new learning throughout one’s lifetime, at least under normal conditions. Certain neurological diseases, such as Alzheimer’s disease, can greatly diminish the capacity for new learning.

Amnesia

Amnesia, loss or impairment of memory. Amnesia is usually associated with some form of brain damage, but it may also be caused by severe psychological trauma. Amnesia with a physical cause is called organic amnesia, whereas amnesia of psychological origin is called functional amnesia.

Amnesia varies in its degree of severity. For example, a mild concussion may cause a person to forget recent events, but the memory loss may last only for several hours. On the other hand, severe head injuries may lead to permanent memory loss and an inability to learn new information. Amnesic individuals may retain normal cognitive abilities in other areas, such as language.

Anterograde amnesia is impairment in the ability to lay down new memories. It typically results from damage to the areas of the brain involved in long-term memory, including the hippocampus, the temporal lobes, and the frontal lobes. Such damage may result from brain infection (encephalitis), alcoholism, stroke, anoxia (severe oxygen deprivation), or head injury. An individual with severe anterograde amnesia might spend an entire day with a person and then, within a brief time, totally fail to recognize that person. Retrograde amnesia refers to difficulties in recalling or recognizing past events and experiences. It typically accompanies anterograde amnesia and is especially common following concussive head injury. A person with retrograde amnesia has trouble remembering recent events, events from further in the past, or both.

Amnesia is a symptom rather than a disease, and treatment attempts to determine and remove the basic cause. No treatments available will bring back the memory capacity of brain-damaged patients. However, these patients can be helped to make better use of their remaining memory skills. The most effective methods rely on memory aids, ranging from simple devices such as notebooks and timers to computer-based organizers and paging systems. Given such help, a severely amnesic person may be able to live independently.

See also Memory.

Concussion of the Brain

Concussion of the Brain, injury to the brain from a fall or a blow to the head, usually with loss of consciousness, the reason for which is not entirely understood. Increased pressure on the brain stem probably accounts for the slowing or temporary suspension of respiration and the reduced pulse rate that accompany a concussion; additional symptoms include pallor, sweating, and a drop in blood pressure. Dizziness, nausea, and a dull, restless feeling often follow a return to consciousness. Aftereffects such as headaches, dizziness, and nervousness may continue for several days, weeks, or even years after the initial injury. A concussion may temporarily or permanently damage nerve tissue, producing amnesia, irritability, and fatigue; memory is often impaired. Recovery from a concussion is generally complete and prompt after less severe injuries.

Headache

Headache, pain in any part of the head. Although the condition is widespread, less than 1 percent of all headaches indicate serious physical problems. This small percentage includes headaches caused by, or occurring after, concussion or injury to the head (see Concussion of the Brain), meningitis, encephalitis, stroke, or brain tumors. Headache may also accompany misalignment of the jaw or teeth. Short-lived headaches may occur after eating very cold foods or foods high in nitrites or monosodium glutamate. Caffeine withdrawal also may provoke headaches.

The majority of headaches belong to one of three main groups: migraine, a recurrent, severe headache, usually with throbbing on one side, accompanied by nausea and sometimes impaired vision; cluster, similar to migraine, but of short duration, occurring daily in series over weeks or months and predominantly in the area of one eye; and tension, a headache without consistent location thought to result from contractions of the face, scalp, or neck muscles.

Headaches are so common, and sometimes so difficult to alleviate, that several major clinics are devoted solely to their treatment. Most tension headaches respond to mild analgesics such as aspirin and acetaminophen. Severe migraine and cluster headaches do not respond to aspirin, but can be relieved by a variety of medications that affect the expansion or contraction of blood vessels. Headaches of all three major categories have been relieved in many cases with biofeedback techniques.

Migraine

Migraine, severe headache that occurs periodically and is sometimes confined to only one side of the head. A migraine is characterized by intense, throbbing, often blinding pain, and one or more of the following symptoms: sensitivity to light, nausea, vomiting, chills, facial swelling, tenderness of the scalp, sweating, frequent urination, irritability, visual hallucinations, and malaise. The headache may be preceded by a warning sensation, known as an aura, that may include flashes or patterns before the eyes, illusory tastes or odors, dizziness, tingling, or numbness.

At the onset of a migraine headache, blood vessels within the head constrict, causing a decrease in blood flow to the surface of the brain. Swelling of blood vessels in the head and scalp then sets off a chain of reactions that result in the headache. Among the biochemical changes associated with migraines are a reduced level of the neurotransmitter serotonin as well as an insufficient supply of enkephalins, the brain’s pain-relieving chemicals.

Hormonal level changes (such as those experienced by women during menopause or menstruation), endocrine imbalances, and stress due to anything from overwork to loud noises are considered precipitating factors of migraine headaches in susceptible people. Other factors that may trigger attacks include allergies, excess carbohydrates in the diet, foods rich in the trace element iodine, and alcoholic beverages.

Several treatments have been successful in helping migraine sufferers. These include medications such as sumatriptan and ergotamine tartrate, both of which shrink swollen blood vessels, thereby aborting the acute phase of a migraine attack; and propranolol, which stabilizes blood vessel tone and helps prevent subsequent attacks. Other drugs often prescribed to migraine sufferers are amitriptyline, phenelzine, and verapamil. Biofeedback techniques have also proven useful.

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