memory

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The ability to store and access information that has been acquired through experience. Memory is a critical component of practically all aspects of human thinking, including perception, learning, language, and problem solving. See also Perception.

Stages

The information-processing approach divides memory into three general stages: sensory memory, short-term memory, and long-term memory. Sensory memory refers to the sensations that briefly continue after something has been perceived. Short-term memory includes all of the information that is currently being processed in a person's mind, and is generally thought to have avery limited capacity. Long-term memory is where all the information that may be used at a later time is kept.

A number of interesting facts are known about sensory memory, including the following: (1) sensory memories appear to be associated with mechanisms in the central nervous system rather than at the sensory receptor level, and (2) the amount of attention that a person pays to a stimulus can affect the duration of the sensory memory. Although all of the functions of sensory memory are not understood, one of its most important purposes is to provide people with additional time to determine what should be transferred to the next stage in the memory system, that is, short-term memory.

Information obtained from either sensory memory or long-term memory is processed in short-term memory in order for a person to achieve current goals. In some situations, short-term memory processing simply involves the temporary maintenance of a piece of information, such as remembering a phone number long enough to dial it. Other times, short-term memory can involve elaborate manipulations of information in order to generate new forms. For example, when someone reads 27 + 15, the person manipulates the symbols in short-term memory in order to come up with the solution. One useful manipulation that can be done in short-term memory is to reorganize items into meaningful chunks. For example, it is a difficult task to keep the letters S K C A U Q K C U D E H T in mind all at once. However, if they are rearranged in short-term memory, in this case reversing them, they can be reduced to a single simple chunk: THE DUCK QUACKS. Short-term memory can accommodate only five to seven chunks at any one time. However, the amount of information contained in each chunk is constrained only by one's practice and ingenuity. In order to increase the amount of information that can be kept in short-term memory at one time, people need to develop specific strategies for organizing that information into meaningful chunks. In addition, many studies have also demonstrated that the transfer of information from short-term to long-term memory is much greater when the information is manipulated rather than simply maintained.

One can keep massive amounts of information in long-term memory. In general, recall from long-term memory simply involves figuring out the heading under which a memory has been filed. Many tricks for effective retrieval of long-term memories involve associating the memory with another more familiar memory that can serve as an identification tag. This trick of using associations to facilitate remembering is called mnemonics. Long-term memory stores related concepts and incidents in close range of one another. This logical association of memories is indicated by subjects' reaction times for identifying various memories. Generally, people are faster at recalling memories if they have recently recalled a related memory. One good way to locate a long-term memory is to remember the general situation under which it was stored. Accordingly, techniques that reinstate the context of a memory tend to facilitate remembering.

Sometimes information may not have been filed in long-term memory in the first place, or if it has, is inaccessible. In these situations, the long-term memory system often fills in the gaps by using various constructive processes. One common component to memory constructions is a person's expectations. Countless studies have also indicated that memories tend to systematically change in the direction of a prior expectation or inference about what is likely to have occurred.

Physiology

A number of physiological mechanisms appear to be involved in the formation of memories, and the mechanisms may differ for short-term and long-term memory. There is both direct and indirect evidence suggesting that short-term memory involves the temporary circulation of electrical impulses around complex loops of interconnected neurons. A number of indirect lines of research indicate that short-term memories are eradicated by any event that either suppresses neural activity (for example, a blow to the head or heavy anesthesia) or causes neurons to fire incoherently (for example, electroconvulsive shock). More direct support for the electric circuit model of short-term memory comes from observing electrical brain activity. By implanting electrodes in the brain of experimental animals, researchers have observed that changes in what an animal is watching are associated with different patterns of circulating electrical activity in the brain. These results suggest that different short-term memories may be represented by different electrical patterns. However, the nature of these patterns is not well understood. See also Electroencephalography.

Long-term memories appear to involve some type of permanent structural or chemical change in the composition of the brain. This conclusion is derived both from general observations of the imperviousness of long-term memories and from physiological studies indicating specific changes in brain composition. Even in acute cases of amnesia where massive deficits in long-term memory are reported, often, with time, all long-term memories return. Similarly, although electroconvulsive therapy is known to eliminate recent short-term memories, it has practically no effect on memories for events occurring more than an hour prior to shocking. Thus the transfer from a fragile short-term memory to a relatively solid long-term memory occurs within an hour. This process is sometimes called consolidation. See also Electroconvulsive therapy.

The nature of the “solid” changes associated with long-term memories appears to involve alterations in both the structural (neural connections) and chemical composition of the brain. One study compared the brains of rats that had lived either in enriched environments with lots of toys or in impoverished environments with only an empty cage. The cerebral cortices of the brains of the rats from the enriched environment were thicker, heavier, endowed with more blood vessels, and contained significantly greater amounts of certain brain chemicals (such as the neurotransmitter acetylcholine). Other researchers have observed that brief, high-frequency stimulation of a neuron can produce long-lasting changes in the neuron's communications across synapses.

Researchers believe that different brain structures may be involved in the formation and storage of long-term memories. The hippocampus, thalamus, and amygdala are believed to be critical in the formation of long-term memories. Individuals who have had damage to these structures are able to recall memories prior to the damage, indicating that long-term memory storage is intact; however, they are unable to form new long-term memories, indicating that the long-term memory formation process has been disrupted. It is not known where long-term memories are stored, but they may be localized in the same areas of the brain that participated in the actual learning. See also Brain.

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(1) See memory card and flash memory.

(2) The computer's workspace, which is physically a collection of dynamic RAM (DRAM) chips. A major resource in the computer, memory determines the size and number of programs that can be run at the same time, as well as the amount of data that can be processed instantly.

It All Takes Place in Memory

All program execution and data processing takes place in memory, often called "main memory" to differentiate it from the memory chips on other circuit boards in the machine. The program's instructions are copied into memory from disk, tape or the network and then extracted from memory into the CPU's control unit circuit for analysis and execution. The instructions direct the computer to input data into memory from a keyboard, disk, tape, modem or network.

Calculate, Compare and Copy

As data are entered into memory, the previous contents of that space are lost. Once the data are in memory, they can be processed (calculated, compared and copied). The results are sent to a screen, printer, disk, tape, modem or network.

Memory Is An Electronic Checkerboard

Think of memory as a checkerboard, each square holding one byte of data or instruction. Each square has a separate address like a post office box and can be manipulated independently. As a result, the computer can break apart programs into instructions for execution and data records into fields for processing. See early memories and RAM.

A Checkerboard of Bytes

Each checkerboard square of memory holds one byte. The contents of any single byte or group of bytes can be calculated, compared and copied independently. That is how fields are put together to form records and broken apart when read back in. On a disk, data are stored in sectors, typically 512 bytes long, that are the smallest unit that can be read or written by the drive.

Memory Does Not Remember

Oddly enough, the computer's memory does not "remember" anything when the power is turned off. So why do they call it memory? Because the first memory did "remember," but today's RAM chips do not, which is why files have to be saved before the application is ended. Although there are memory chips that do, in fact, hold their content permanently (ROMs, EEPROMs, flash memory, etc.), they are used for internal control purposes and data storage, not for processing. To make it even more confusing, it is likely that memory in the future will again "remember" (see future memory chips). See storage vs. memory.

The main "remembering" memory in a computer system is its hard disks, and although they are sometimes called "memory devices," many prefer to call them "storage devices" (as we do) in order to differentiate them from internal RAM memory.

Memory Can Get Clobbered!

Memory is an important resource that cannot be wasted. It must be allocated by the operating system as well as by applications and then released when not needed. Errant programs can grab memory and not let go, which results in less and less memory available to other programs. Restarting the computer gives memory a clean slate, which is why rebooting the computer clears up so many problems with applications.

In addition, if the operating system has bugs, a malfunctioning application can write into the same memory used by another program, causing all kinds of unspecified behavior. You discover these bugs when the system freezes or something weird happens all of a sudden. If you were able to look into memory and watch how fast data and instructions are written into and out of it in the course of just a single second, you would realize that it is a miracle it works at all.

Other terms for the computer's main memory are RAM, primary storage and read/write memory. Earlier terms were core and core storage. See dynamic RAM, static RAM and memory module.

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Space within a computer where information and program are stored while being actively worked on; also called core. It is expressed in terms of the number of characters (bytes) that can be retained. The memory of the computer is in the form of read-only (ROM) and ram (random - access memory) or read/write memory. It is this memory facility that distinguishes the computer from devices such as calculators and bookkeeping machines, which, although they have input, output, and processing capabilities, cannot store programs internally within the processing unit.

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Life is unpredictable. But memory provides organisms with the ability to learn — to modify their behaviour in the light of experience — and hence to reduce their uncertainty about the world. This is clearly an important behavioural adaptation, from the point of view of evolution. Indeed, most animals exhibit some forms of learning and memory, ranging all the way from gradual weakening (habituation) or strengthening (sensitization) of simple reflex actions, to conscious recollection of personal experiences.

We can remember a telephone message for the few seconds it takes to write it down. But we can also remember things over very long periods of time. For example, adults may still remember some of the things they were taught at school — both general abilities, such as how to add numbers together, and specific things, such as the translation of ‘la plume de ma tante’. Additionally, we can also remember (though unconsciously) many of the skills attained through life, such as how to ride a bicycle or play the piano. There are many different ways in which humans and other animals remember things. It follows that memory cannot be conceptualized simply and that there are likely to be a variety of different, interacting memory systems.

Much of our sense of who we are as individuals depends on a particular kind of memory, involving recollection of our own past experiences, feelings, and relationships. One only has to imagine not being able to recall what has happened in one's past, or whether or not one even has family and friends, to realize how disruptive and distressing severe amnesia (such as occurs in Alzheimer's disease) can be, both to the patients themselves and to those close to them.

Psychologists have long drawn distinctions between different types of memory systems and memory processes. As early as 1890 William James distinguished between ‘primary memory’ (information one is presently aware of) and ‘secondary memory’ (information in the psychological past). Current ideas still maintain a distinction between short-term memory and long-term memory, evidenced by impairments of one or the other in brain-damaged patients. However, early ‘multistore models’, which proposed separate short-term and long-term memory stores, have now been discredited as being too simplistic.

The idea of a unitary short-term store has now largely been replaced by the concept of ‘working memory’. The working memory system is concerned with both active processing and short-term storage of information and allows one to plan for the future and to bring together thoughts and ideas. Damage to the frontal lobes seems to impair working memory: patients with such damage function rather normally apart from being impaired in the use of stored knowledge to guide appropriate behaviour. Experiments on monkeys have shown that individual nerve cells in certain parts of the frontal cortex not only fire impulses when certain objects are seen by the monkey but continue to respond when the object disappears from view, as if holding a memory of the object. Furthermore, studies on the effects of damage of the frontal lobes in monkeys suggest that different forms of working memory can be localized to specific regions of the prefrontal cortex — the front part of the frontal lobes.

The concept of a single long-term store has also been replaced, by the view that there are several interacting long-term memory systems. There have been many attempts to subdivide long-term memory, but none has proved entirely successful. Another early distinction was between ‘episodic memory’ and ‘semantic memory’. Episodic memory is autobiographical recollection of personally experienced events (such as what you had for breakfast), whereas semantic memory is general knowledge about the world, factual information and its meaning (such as the fact that breakfast is a kind of meal). Despite a clear conceptual difference, there is less evidence that these two types of memory rely on different memory systems in the brain. Indeed, semantic and episodic memory would appear to be strongly interdependent. For instance, retrieving semantic information may depend upon recalling the particular episodic event or events during which the semantic knowledge was gained. Likewise, it has been argued that recalling an episodic event (for example, remembering seeing an elephant at the zoo) depends on intact semantic memory (the definition of an elephant). Both types of memory may therefore rely on common underlying neural structures.

An alternative distinction was made between ‘declarative memory’ and ‘procedural memory’. Declarative memory refers to knowing ‘what’, and includes both semantic and episodic information, whereas procedural memory refers to knowing ‘how’, and relates to skilled behaviour without the need for conscious recollection, such as the ability to remember how to drive a car. Support comes from observation of certain patients with amnesia who seem to have relatively intact procedural learning abilities (they can still learn how to do things) in the face of impaired declarative learning (e.g. not remembering where they are). However, the distinction between declarative and procedural knowledge is imprecise and many kinds of behaviour involve aspects of both. Furthermore, some patients with severe amnesia are capable of certain feats of memory (such as learning new factual information) that cannot be explained by procedural learning alone.

A further theoretical distinction was made between ‘explicit memory’ and ‘implicit memory’. Explicit memory is said to be involved in tasks that require conscious recollection of previous experiences, whereas tasks that are facilitated in the absence of conscious recollection are said to depend on implicit memory. Many traditional methods used to test memory involve the person being asked to remember specific experiences, and are therefore measures of explicit memory. For instance, the memory of a previously-seen list of words could be tested by free recall (‘Tell me the words that were on that list you saw earlier’), by recognition (‘Was this word among the list you saw?’), or by cued recall (‘Complete these letters to form a word that occurred on the list’).

To demonstrate implicit memory it is necessary to show that a person has a long-term memory of a past experience although they can't consciously recall it. For example, the perceptual identification of words presented extremely briefly is easier if the words have previously been seen. Amnesic patients perform relatively normally on such ‘repetition priming’ tasks, as well as being able to acquire new motor skills, yet they are impaired on most tests of explicit memory. However, the distinction between explicit and implicit memory is again rather general and does not account for all of the patterns of long-term memory performance in amnesic subjects. Furthermore, the theory does nothing to address the fact that amnesic subjects can still form conscious short-term memories, which clearly involve explicit learning.

Observations that amnesic patients can retain some information briefly but not for long periods of time led to the development of the ‘consolidation theory’. This suggests that immediate experiences are somehow crystallized into long-term memory, and that this process is disrupted in amnesia. The theory also maintains that the process of memory consolidation occurs over a period of time, during which memory traces are particularly vulnerable to permanent disruption by such things as a blow to the head, certain drugs, electric shock to the brain, etc. However, consolidation theory cannot account for the fact that apparently lost memories can sometimes be retrieved subsequently.

‘Context-dependent theories’ on the other hand propose that each memory trace (for instance of a particular person) is encoded together with information about the associated context (where you met the person), and that subsequent retrieval of the memory may be facilitated by reinstating the context. (Everyone is familiar with the fact that it is difficult to remember the names of even close friends when you meet them in unexpected places.) This theory is supported by the remarkable observation that divers recall more words learnt underwater when subsequently tested underwater than when tested on land, and vice versa. Learning while under the influence of certain drugs is also context-dependent, being better recalled when the same drug is administered.

Related ‘state-dependent theories’ maintain that agents or procedures that induce amnesia do not permanently disrupt memories but rather ‘re-encode’ the memory traces in association with the brain state induced by the amnesic agent or procedure. Patients who have electroconvulsive shock (for instance, to treat depression) often complain of loss of memories; and this procedure indubitably disrupts long-term memory when given experimentally to rats. But rats can retrieve their lost memories after a subsequent shock, because this puts the brain back into the condition in which the information was ‘re-encoded’, thereby providing an additional cue to aid remembering.

Although it is hard to verify whether a deficiency of memory reflects re-encoding or permanent memory loss, the importance of forgetting should not be underestimated. Although the brain has a huge capacity for memories, it must be finite. Since the brain appears to be able to form associations between disparate stimuli very easily, so it is important for it to be able to forget meaningless or arbitrary associations and remember only those associations that prove consistent or relevant. It has been theorized that inappropriate associations in the brain may specifically be weakened during the phase of sleep in which rapid eye movements and vivid dreams occur (REM sleep).

It is intuitively obvious that memories of all sorts involve functional changes in the brain, sometimes occurring remarkably quickly. Much of what we know about learning and memory has been gained from clever experiments involving the training of animals, both intact and with brain damage, as well as from studies of normal and amnesic human beings. But over the past few decades neurophysiologists and molecular biologists have made great strides in their understanding of the cellular mechanisms of learning and memory. One fruitful approach has involved examining basic forms of learning in animals with relatively simple nervous systems, such as the marine snail Aplysia. This animal withdraws its gill apparatus reflexly when the ‘mantle’ around it is touched, and the circuit of sensory and motor nerve cells responsible for this has been defined. This reflex is subject to habituation (if the touch to the gill is repeated time after time), and to sensitization (if the touch is coupled with other stimulation).

It turns out that these simple forms of short-term implicit learning involve changes in the effectiveness of synaptic transmission (mainly changes in the amount of transmitter substance per nerve impulse released at a particular synapse in the circuit). Longer-term memory requires new protein synthesis and the growth of new or larger synapses.

More complicated forms of learning may involve elaboration of a common set of molecular mechanisms. For instance, most animals can learn to associate one stimulus with another (such as the association formed between the sound of a bell and the sight of food in Pavlovs' famous experiments on classical conditioning). The underlying neural change, just as for sensitization in Aplysia, is thought to involve increased release of transmitter substance at synapses in the circuit associating the two forms of stimulation.

In recent years, attention has focused on a primitive part of the cerebral cortex called the hippocampus, which is tucked inside, under the lower edge of the temporal lobe of the cerebral hemispheres. Extensive damage to this general region in humans can cause devastating retrograde amnesia, which virtually eliminates the capacity to form new long-term conscious memories, while leaving old semantic and personal memories relatively intact. Traditionally, the hippocampus itself has been considered the seat of human episodic memory. However, recent research with monkeys has revealed several, functionally dissociable memory systems in this region of the temporal lobe. These include the perirhinal cortex, for object memory, and the amygdala, for memory for the emotional significance of stimuli and events. These individual areas, each with its different specialization, may then contribute to a broader-based temporal lobe memory system providing the basis of both episodic and semantic memory. The monkey's hippocampus may have a relatively restricted role in memory for spatial location.

In rodents, the hippocampus certainly seems particularly involved in spatial memory: when it is damaged, rats and mice cannot remember their way around mazes. It turns out that the connections between certain nerve cells in the hippocampus are remarkably ‘plastic’. Synapses can be strengthened simply by a brief burst of nerve impulses, so that single impulses will subsequently (and for very long periods of time) evoke much bigger electrical responses in the receiving cell. Much is now known about the molecular basis of this phenomenon, called long-term potentiation. This mechanism may provide the basis of, or at least contribute to, many forms of learning, in several different regions of the brain, ranging from perceptual learning in young animals to human explicit memory.

Memory is central to the human condition and has been investigated at many levels. Neuroscientists have studied the molecular and cellular mechanisms of memory in animals and humans, and psychologists have contributed to our understanding about the different kinds of processes involved in memory through research with amnesic patients and normal subjects. Temporal lobe dysfunction is commonly associated with declarative or explicit memory impairments. However, since most amnesic patients either exhibit diffuse brain damage (Korsakoff's syndrome) or have focal damage to a range of different structures, our present understanding of which particular neural systems are important for different memory processes has come predominantly from animal ‘models’ of human amnesia.

— Mark J. Buckley

Bibliography

• Bolhuis, J. (2000). Brain, perception, memory: advances in cognitive neuroscience. Oxford University Press.
• Eysenck, M. W. (1995). Cognitive psychology: a student's handbook, (3rd edn). Erlbaum, Hove

See also amnesia; brain; cerebral cortex; limbic system.

noun

1. The power of retaining and recalling past experience: recall, recollection, remembrance, reminiscence. See remember/forget.
2. An act or instance of remembering: recollection, remembrance, reminiscence. See remember/forget.

n

Definition: ability to hold in the mind
Antonyms: amnesia, forgetfulness, ignorance

The quality of a material that enables it to return to its original shape after it has been compressed or stretched.

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The power of the mind to think of a past that no longer exists poses both empirical, psychological problems, and more abstract philosophical ones. The scientist wants to know how the brain stores its memories, and whether the mechanism is similar for different types of memory, such as short-term and long-term memories. The philosopher is particularly puzzled by the representative power of memory. That is, if I summon up a memory of some event, how do I know to interpret it as representing the past, rather than being a pure exercise of imagination? Is there a specific ‘feeling of pastness’? But if so, might I not then have the feeling, but not know to interpret that as a feeling of pastness? Indeed, is there always a present representation, or might memory be a form of direct acquaintance with the past? This might at least give us a justification of the confidence we place in memory. But is not the sceptical hypothesis proposed by Russell, that the earth might have sprung into existence five minutes ago, with a population that ‘remembers’ a wholly unreal past, at least logically possible? But if it is logically possible, the question of how we know that this is not what has happened is set to look intractable.

The mental faculty that facilitates storage and retrieval of information that has been learned, such as sport knowledge or a motor programme. According to the black box theory, memory has been viewed as consisting of three components short-term sensory store short-term memory, and long-term memory. The hippocampus of the limbic system plays an important part in memory. The exact way in which the brain stores information is unknown, but it may involve chemical or structural changes. See also engram, memory-drum theory.

Memory
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If one views memory as the ability to retain and recall past states of consciousness, then psychoanalysis has played a considerable role in its delineation. But in terms of memory theory considered more broadly, its significance is much more modest. Freud approached memory from three perspectives. In terms of neurology, his contributions were original but limited. From the standpoint of psychology, he added to the pre-existing framework. Finally, in creating the psychoanalytic perspective, Freud essentially reworked views that had been extensively discussed in philosophy, literature, and scientific research.

In 1891 Freud's On Aphasia: A Critical Study (1891b) proposed a solution to the problem of memory retrieval and disorders of memory, which was much discussed at the end of the nineteenth century following the discoveries of Paul Broca. Freud did not take sides in the dispute between Broca, who localized language function to a specific cerebral area, and Carl Wernicke, who developed the functional concept of conduction aphasia. Freud's solution, which resembled the one that Henri Bergson adopted five years later in Matter and Memory, could serve as the basis for a dialogue between neurology and philosophy. But the 1891 text is a pre-psychoanalytic work.

Freud's second, psychological perspective finds him apparently subscribing to the theory of memory traces. Already expressed in its major outlines in Plato's Theatetus, this theory was commonplace in the nineteenth century, when the vogue for scientific materialism made it seem self-evident (although spiritualists also accepted it). In this sense Freud is close to his contemporary, Théodule Ribot, but for Freud the theory of memory traces assumed a specific form intended to account for the role the unconscious plays in remembering. This led to Freud's Project for a Scientific Psychology of 1895 (1950c [1895]) and the best expression of the doctrine, in chapter 7 of The Interpretation of Dreams (1900a). The "Mystic Writing Pad" (1925a) represents an attempt to provide the theory of memory traces and process of memory retrieval with a metaphor suitable for psychoanalysis. But in these texts, Freud was concerned to place facts revealed by psychoanalysis within the framework of conventional psychological theory; he made no effort to create a new "theory of memory."

Much more familiar (and often wrongly considered as the specific psychoanalytic contribution to problems of memory) is the third perspective, involving the alleviation of pathological symptoms by recalling forgotten traumata. Freud himself did a great deal to promote this point of view through the significance he attached in numerous of his writings to Josef Breuer's treatment of Anna O. Too common is the impression that the famous formula "hysterics suffer mainly from reminiscences" (Studies on Hysteria, 1895d, p. 7) expresses the most fundamental idea in psychoanalysis.

There is no question that the idea of recollection constitutes an essential part of psychoanalytic therapy, and to think otherwise is to betray Freud in a fundamental way. Serge Viderman's claim in La Construction de l'espace analytique (1970) that the search for lost memories is one of Freud's youthful illusions to be replaced, in analysis, with co-constructions of subjectivity, is simply an attempt to employ non-analytic therapy, proposed in the past by such authors as Karen Horney. Until the end of his life Freud remained attached to this model: trauma / repression / forgetting / symptom / remembering / healing. In 1937, in "Analysis Terminable and Interminable," he went so far as to say that, like hysterics, psychotics also suffer from reminiscences, implying that certain delusional representations were, in fact, the reappearance in consciousness of past experiences unrecognized as such. Between Anna O. and this late text, Freud's entire body of work is sprinkled with thoughts along these lines. In "Remembering, Repeating and Working-Through" (1914g), for example, he resolved the conflict between impossible access to memory and the sterility of repetition through the introduction of what he called "working through" (Durcharbeitung). Further proof is found in his "A Disturbance of Memory on the Acropolis" (1936a), in which Freud displaces the memory trauma (thinking the Acropolis did not exist) onto another type of fact (fear of surpassing the father). The "search for lost time," the attempt to alleviate repression that has produced a failure of memory and the associated symptom, is one of the major themes of Freudian psychoanalysis. However, reservations are in order regarding its originality and theoretical scope.

Even though Freud often felt that the cure for hysterical symptoms through recollection of repressed traumatic memories could be presented as a revolutionary discovery, such figures as Janet and other late nineteenth-century psychotherapists viewed the idea and even the method as commonplace. The idea can even be traced back much further. For example, in a letter to Pierre Chanut, dated June 6, 1647, René Descartes recounts that his penchant for girls with a squint came to an end with his recollection of a childhood memory. Descartes's interest in such women may not have been a true hysterical symptom, but the link between current behavior and its origin in the past is indicated along with all the characteristics (forgetting, unconsciousness, healing through remembrance) that Freud would later employ. Much earlier, Plato, in the Phaedrus, interpreted the process of falling in love in a similar manner. In short, there is no end to the number of literary, philosophical, and clinical sources for what is often considered the most significant psychoanalytic contribution to the theory of memory.

More plausibly, psychoanalysis lent to a certain type of amnesia and memory retrieval an unanticipated practical (therapeutic) scope. Its importance was practical. Although it constitutes an original theoretical point, it does not amount to a global theory such as those developed by philosophers and psychologists. However, it has a good fit with such theories. It works, for example, within the framework that Henri Bergson described and interpreted in Matter and Memory.

Bibliography

Bergson, Henri. (1896). Matter and memory. New York: Zone Books, 1988.

Freud, Sigmund. (1891b). On aphasia; A critical study. New York: International Universities Press, 1953.

——. (1900a). The interpretation of dreams. Part I, SE,4: 1-338; Part II, SE, 5; 339-625.

——. (1914g). Remembering, repeating and working-through (Further recommendations on the technique of psycho-analysis II). SE, 12: 145-156.

——. (1925a). A note upon the "mystic writing pad." SE, 19: 225-232.

——. (1936a). A disturbance of memory on the Acropolis. SE, 22: 239-248 ——. (1937c). Analysis terminable and interminable. SE, 23: 209-253

—YVON BRÈS

This entry consists of the following articles:

• Memory: Autobiographical Memory
• Development of Memory
• Memory: Graphics, Diagrams, and Videos
• Memory: Implicit Memory
• Memory: Mental Models
• Memory: Metamemory
• Memory: Myths, Mysteries, and Realities
• Memory: Structures and Functions

When we learn something there must be a change in the brain, but no one knows what the change is. Until quite recently the concept of memory was used only in mentalistic contexts. Few dictionaries contain any reference to memory as a feature of a physical system, though we now have the language of computer scientists to help us in thinking about our own memories, as physical records in the brain. In computer language the memory is an instrument in which is placed a store of whatever information is to be used for calculation. This information is thus a representation of some set of events, embodied in a code. How does the nervous system come to contain useful representations of its environment?

The code of the nervous system is provided basically by the fact that each nerve fibre carries only one sort of information. In such a system learning must consist of a change in the connection pattern of the pathways from input (say the eyes) to output (say movement). The initial basis of the nervous memory is thus provided by heredity (the genetic memory), which establishes the nervous pathways of the newborn. Natural selection has ensured that at birth each individual is provided with potentialities suitable for its future type of environment. A young kitten already has the connections which ensure that each cell of its visual cortex responds mainly when a particular contour moves in front of its eyes, though the responses are less vigorous than they are in an adult. If the kitten is only allowed to see vertical lines then it will later be found to lack the power to respond to horizontal (or other) lines. Meanwhile the response to vertical contours has become much stronger. (See visual system: environmental influences). Memory thus depends upon selection from the original multiplicity of possible actions of those that represent useful responses to the environment. Other work with kittens shows that normal capacities only develop if there is appropriate input at certain short critical periods. (See spatial coordination.)

A human child similarly is born with a range of capacities, and given the right stimulus he then learns to take those actions that are appropriate (see infancy, mind in). Thus from 12 months onwards he learns to speak whatever language he hears, making certain vocal movements and rejecting others. All skills involve such selection. As development proceeds we thus build a model in the brain that ensures appropriate behaviour. The problem of memory is to find the mechanism that increases the probability of use of some pathways and decreases that of others.

The decision as to whether a nerve cell is to send a signal depends upon the synapses that it receives from other nerve fibres. It was early suggested by the histologist Ramón y Cajal that memory depends upon forming synapses. By contrast, Ivan Pavlov, who pioneered the physiological study of learning, attributed the 'conditioned reflexes' in his dogs to vague processes of spread of excitation and inhibition in the cortex. These two types of theory persist to the present. The majority of neuroscientists probably believe in a synaptic change, but there is little direct evidence of the details of it.

The nervous system contains many pathways that re-excite themselves, and it was suggested that these might serve for memory in the brain, as in some computers. This is not likely to be true for long-term memories, which must surely be physically embodied, since they can endure for up to 100 years, in spite of shocks and anaesthetics and (in rats) even freezing. But it frequently happens that immediately after a shock there is no memory, say of an accident (see amnesia). It is therefore postulated that memory is recorded on two or more time scales. The short-term memory is transient and easily interrupted. Perhaps it is carried by the chains that re-excite themselves. It must endure for long enough to allow a record to be 'printed' in the long-term memory. This may involve synaptic change, perhaps by some sort of growth process. Parts of the brain concerned with memory contain many very small nerve cells ('amacrine cells' or 'microneurons'). One suggestion is that these serve to produce an inhibitory substance whose action closes the unwanted pathway. This would allow the other one to be used: its synapses would then become more effective and those of the other pathway would wither away. All such changes would involve synthesis of new protein, and there is evidence that, if a substance inhibiting protein synthesis is given shortly after a learning occasion, no memory is established. This does not mean that the new protein carries the memory. It alters the probability of use of one set of channels rather than another. Information in the brain is coded by channels not molecules. Not appreciating this, biochemists have sought for a memory molecule, on the mistaken analogy of DNA. They have even claimed that memory can be transferred by injecting extracts from a trained brain, or even by the cannibalism of worms. Many injected substances will indeed change brains, but the claims of transfer of specific memories have not been substantiated. The attraction of the idea of cannibalism tells more about human psychology than about the biology of memory.

The capacity to change nervous pathways, that is to learn, is quite widespread. A cockroach without its head will learn not to dip its leg into water from which it gets a shock. From such simple learning systems it has been discovered that various changes in the electrical and chemical properties of the nerve cells are involved. But memories like our own usually store more complicated information, and this involves special nervous equipment. In each species the brain has a memory system suitable to its special way of life. Memories are not parts of a generalized computer system but specific analogue devices. In octopuses we have been able to find two anatomically distinct memory mechanisms. In one are stored records of objects seen and in the other records of objects touched or tasted. The decisions that an octopus makes are rather simple — whether to attack a particular object or to draw in an object touched with its arms. It can learn to attack a horizontal rectangle and avoid a vertical one or to discriminate between rough and smooth spheres. (See invertebrate learning and intelligence.) Such choices are typical of the selections between alternatives that are the essential features of recording in memory. The animal or man must be provided with feature detectors that can allow the performance of two or more actions. Learning which action to perform must depend upon a system that allows for information about past results to alter the probabilities of the use of the pathways in the future. We believe that this is done by initially reducing the effectiveness of the wrong pathway and then increasing the right one — perhaps by new synaptic growth. Many special features are required to make such a system effective, and it is not surprising that neuroscientists have not yet fully unravelled the secret of the memory mechanism. And, of course, in mammals memory does not depend upon switching single neurons, say in the visual cortex, but somewhere the pathways are changed when we learn.

There must be nervous tracts that bring information such as that of taste or pain together with signals from the outside world. In mammals there is evidence that these come through the reinforcement pathways, which can be activated by self-stimulation for reward. These lead through the hypothalamus to the hippocampus, which is a part of the brain particularly concerned with memory.

Another special need is for mechanisms of generalization in the memory, and here the octopus has proved most helpful. It does not have to learn everything eight times over. Martin Wells was able to show that what is learned by one arm can be performed by the others — but not if a particular piece of the brain is removed. This piece, the median inferior frontal, has a weblike structure that allows signals from the different arms to interact. This is one small example of how study of parts of the brain can tell us about the memory mechanism. Again, in an octopus the visual memory can be removed without damaging the touch memory, and vice versa. So the memory record in the octopus brain is localized. In mammals it has proved difficult to find where the record is, so that the psychologist Karl Lashley, after his lifelong 'search for the engram', could not decide whether it was nowhere in the brain or everywhere.

The model of the mnemon, or unit of memory, can be considered either as an anatomical reality, as I believe it to be in the octopus, or as a logical schema representing the much more complex situation in man. The essence of it is that establishing a permanent memory record involves selection from an initial set of possible pathways. Selection is made on a basis of the rewards that follow from different actions. The particular type of memory of each species depends upon modification of the connections of an inborn feature-detector system. In man these detectors are particularly tuned to respond to features of human behaviour. The child is specially sensitive to human speech sounds even at 2 months, long before he can talk or understand speech (see brain development). By learning to react in appropriate ways to particular features he then builds a model in his brain that allows him to live in his human environment. See memory, autobiographical.

(Published 1987)

— J. Z. Young

Bibliography
• Baddeley, A. D. (1976). The Psychology of Memory. (For a comprehensive bibliography.)
• Bartlett, F. C. (1932). Remembering.
• Young, J. Z. (1978). Programs of the Brain.

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IN BRIEF: The act or power of remembering. Also: The part of a computer that stores information.

We can invent only with memory. — Alphonse Karr (1808-1890)

Tutor's tip: The "memoir" (a biography or autobiography) of a person with a bad "memory" (the mental faculty of remembering) is often more fiction than fact -- and usually more entertaining!

LearnThatWord.com is a free vocabulary and spelling program where you only pay for results!

Quotes:

"If you want to win friends, make it a point to remember them. If you remember my name, you pay me a subtle compliment; you indicate that I have made an impression on you. Remember my name and you add to my feeling of importance." - Dale Carnegie

"Memory is the mother of all wisdom." - Aeschylus

"This boy is dead now, I knew it before taking him in my arms, I can remember his face, his suffering, his voice." - Princess of Wales Diana

"If I could remember the names of all these particles, I'd be a botanist." - Enrico Fermi

"I always have trouble remembering three things: faces, names, and -- I can't remember what the third thing is." - Fred A. Allen

"People tend to remember my performances, not me." - Ellen Barkin

See more famous quotes about Memory

The capacity to recall previously experienced sensations, information, data and ideas.

• brain m. — the ability of the brain to use knowledge gained from past experience. This is essential for the process of learning by animals. The process is poorly understood, but its practical application is sophisticated, especially in dogs.
• m. cell — an expanded clone of small lymphocytes derived from stimulated antigen-sensitive B and T lymphocytes. They have antigen receptors of the same specificity as the parent cell. Important in the secondary immune response.
• immunological m. — the ability of the immune system to respond to more strongly and rapidly to the second and subsequent exposures to an antigen.
• suture m. — a property of some synthetic fibers which encourages the spontaneous untying of knots—the ‘memory’ of the fiber is that it is a straight fiber.

n

1. the ability to recall events, experiences, information, and skills. n 2. a general term for a device that stores data in binary code on electronic or magnetic media in computers. n 3. the ability of the immune system to greatly speed up the response to pathogens that have previously been encountered.

For a list of words related to memory, see:

• Memory and Data Storage - memory: internal or external storage area and capacity to store and retrieve binary data and programs; storage

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See words rhyming with "memory."

  See crossword solutions for the clue Computer hardware.

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Dansk (Danish)
n. - hukommelse

idioms:

• external memory    ekstern hukommelse
• from memory    udenad
• in living memory    så langt tilbage nogen kan huske
• in memory of    til minde om
• internal memory    intern hukommelse
• memory board    hukommelseskort
• memory card    hukommelseskort
• within living memory    i mands minde

Nederlands (Dutch)
herinnering, geheugen, nagedachtenis bij mensenheugenis

Français (French)
n. - mémoire, souvenir, commémoration, (Comput) mémoire

idioms:

• external memory    mémoire externe
• from memory    de mémoire
• in living memory    de mémoire d'homme
• in memory of    en mémoire de, en commémoration de
• internal memory    (Comput) mémoire interne
• memory board    (Comput) carte mémoire
• memory card    (Comput) carte mémoire
• within living memory    de mémoire d'homme

Deutsch (German)
n. - Erinnerung, Andenken, Gedächtnis, Speicher

idioms:

• external memory    externer Speicher
• from memory    aus dem Gedächtnis
• in living memory    seit Menschengedenken
• in memory of    zur Erinnerung an
• internal memory    interner Speicher
• memory board    (Comp.) Speicherplatine
• memory card    Speicherkarte
• within living memory    seit Menschengedenken

Ελληνική (Greek)
n. - μνήμη, ικανότητα μνήμης, μνημονικό, ανάμνηση, θύμηση, (τεχνολ.) μνήμη ηλεκτρονικού υπολογιστή

idioms:

• external memory    (Η/Υ) εξωτερική μνήμη
• from memory    από μνήμης
• in living memory    από καταβολής του ανθρώπου
• in memory of    εις μνήμην του, σε ανάμνηση του
• internal memory    (Η/Υ) εσωτερική μνήμη
• memory board    (Η/Υ) κάρτα μνήμης
• memory card    (Η/Υ) κάρτα μνήμης
• within living memory    από καταβολής του ανθρώπου

Italiano (Italian)
memoria

idioms:

• external memory    memoria esterna
• from memory    a memoria
• in memory of    in memoria di
• in/within living memory    a memoria d'uomo
• internal memory    memoria interna
• memory board    banco memoria

Português (Portuguese)
n. - memória (f), recordação (f) (objeto), comemoração (f)

idioms:

• external memory    memória externa (f)
• from memory    de cor
• in memory of    em memória de
• in/within living memory    em memória viva
• internal memory    memória interna
• memory board    placa de memória (f) (Comp.)

Русский (Russian)
память, воспоминания, репутация, регистрация, машинная память

idioms:

• external memory    внешняя память
• from memory    по памяти
• in memory of    в память о
• in/within living memory    на памяти нынешнего поколения
• internal memory    внутренняя память
• memory board    плата памяти

Español (Spanish)
n. - recuerdo, conmemoración, memoria, retentiva

idioms:

• external memory    memoria externa (comput.)
• from memory    de memoria
• in living memory    durante la vida de la presente generación
• in memory of    en memoria de
• internal memory    memoria interna
• memory board    tarjeta de extensión de la memoria
• memory card    tarjeta de memoria
• within living memory    durante la vida de la presente generación

Svenska (Swedish)
n. - minne, hågkomst

中文（简体）(Chinese (Simplified))
记忆, 回忆, 记忆力

idioms:

• external memory    外存存储器, 外置存储器
• from memory    根据记忆
• in living memory    在活着的人们的记忆中
• in memory of    纪念
• internal memory    内部存储器, 内储存器
• memory board    内存板
• memory card    记忆卡
• within living memory    自从记事以来, 在活着的人们的记忆中

中文（繁體）(Chinese (Traditional))
n. - 記憶, 回憶, 記憶力

idioms:

• external memory    外存記憶體, 外置記憶體
• from memory    根據記憶
• in living memory    在活著的人們的記憶中
• in memory of    紀念
• internal memory    內部記憶體, 內儲存器
• memory board    記憶板
• memory card    記憶卡
• within living memory    自從記事以來, 在活著的人們的記憶中

한국어 (Korean)
n. - 기억[력], 추억

idioms:

• in living memory    현존하는 사람들의 기억에 있는
• in memory of    ~을 기념하여

日本語 (Japanese)
n. - 記憶, 記憶力, 記憶の範囲, 死後の名声, 死者への追慕, 思い出, 記憶装置, 記念

idioms:

• from memory    記憶を頼りに
• in memory of    記念して, 追悼して
• memory board    メモリーボード
• read-only memory    読出し専用記憶装置

العربيه (Arabic)
‏(الاسم) ذاكرة, التذكر, يحي ذكرى‏

עברית (Hebrew)
n. - ‮זיכרון, זכר‬

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