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* How the brain works is still much of a mystery to scientists. The nature of memory as a mental faculty is no less intriguing

* Researchers believe that the laying down of memories involves physical and chemical changes at the connections (synapses) between brain cells (neurons)

* When we are born our brains already have almost their full quota of neurons (100 billion)

* It is thought there are three separate systems of memory storage, all of which work in different ways and perform different functions

* A new concept of "working memory" now exercises theorists. It is thought of as a store in which information is manipulated, rather than just deposited

* Some believe that by training the working memory, IQ can be increased Rote learning is a thing of the past, and only the pub quiz now demands an encyclopaedic knowledge of the world's capital cities. Yet teachers and students arguably have more remembering to do than ever before. So how do we store information in our heads for use in the future, and why are some people better at it than others? While scientists are only just beginning to unravel the complex physical and mental systems involved, it seems that certain individuals have always known how to harness the brain's hidden potential.

Learning from slugs

There is always a temptation to explain anything we don't understand in terms of our latest technology. And so we commonly talk about the brain as though it were a desktop computer. But while the computer analogy might be useful for everyday conversation, it quickly breaks down when we examine the physiology of the brain. No magnetic discs or silicon memory chips here, just 100 billion brain cells, or neurons. After more than 30 years of examining the relatively simple brain of a species of sea slug (Aplysia californica has just 20,000 neurons to play with), researchers believe that the laying down of memories involves physical and chemical changes at the synapses, the points of connection - we have 100 trillion of them - between individual neurons. Lasting changes in the relative strength of these connections is now considered to be the most probable explanation for how memories are stored at a cellular level.

At birth, the infant brain already has almost its full quota of neurons, and studies of embryonic brains suggest that, as sensory input begins to flood in, the connections between the groups of cells which process this information are strengthened, while other connections are weakened and some groups of cells die off altogether. Whereas it was once thought that individual memories were stored in specific localities, magnetic resonance imaging of active brains suggests that networks of interconnected cells - so-called neural networks - are involved, and that this structure of interconnections constantly changes to accommodate new memories.

Down memory lanes

If we are still struggling to understand even the basic physiology of the brain, then the nature of memory as a mental faculty is proving no less troublesome. What might seem like a straightforward process - simply remembering something - actually involves three stages: forming the memory, storing it, and then recalling it. And at each stage, the questions mount up. Do we decide what we are going to remember, and if so, how? At what stage is distracting material filtered out (imagine if we remembered everything we heard at a party)? Do we remember sounds, sights and meanings in different ways? How important are associations; between smells and sounds, for example? Scientists believe there are different types of memory, and they give them names such as implicit and explicit, semantic and episodic, declarative and procedural. The last of these, for example, involves the way we retain skills, and it differs from some other types of memory in that it is an unconscious process. To further complicate matters, there seem to be at least three separate systems of memory storage, all of which work in different ways and perform different functions.

A matter of time

Memory storage has long been categorised in terms of its duration. First comes the sensory store, which is thought to retain information from the senses for just a fraction of a second. Next comes short-term memory. But in recent years, a new concept, that of working memory, has exercised the minds of theorists. As its name suggests, working memory is thought of as a store in which information is manipulated, rather than just deposited. It has recently been estimated that no more than seven "chunks" of information can be handled at a time ("chunking" is the process of grouping similar data into units) with the capacity coming down to around four chunks in young adults, and even fewer in the very young and very old.

According to the most popular model, working memory is extremely complex, comprising numerous sub-systems for articulating and maintaining phonological, visual and spatial information, and for sorting relevant from irrelevant data. Just how we keep information in our working memories, by focusing on particular items, or rehearsing them repeatedly (imagine muttering a phone number over and over again until you get to a telephone) are matters for conjecture and debate. But recent studies suggest links between the capacity of an individual's working memory and their performance in tasks such as problem solving and reading comprehension.

Some researchers now believe that by training the working memory, it might even be possible to increase IQ.

Long-term is forever?

While information only resides in short-term or working memory until new information takes our attention, long-term memory might well be permanent, with only our ability to retrieve memories deteriorating over time. And how do some lucky memories make the leap from short-term storage to this long-term Nirvana? It seems that rehearsal helps; maintenance rehearsal (simple recitation) to some extent, but for better results, elaborative rehearsal (thinking about the meaning of the information). Once they have made it into long-term memory, related items seem to be grouped together in conceptual hierarchies, or are linked by association with other concepts through so-called semantic networks. In many cases, whether or not we appear to be blessed with a good memory is likely to depend on the extent to which we take advantage, either consciously or unconsciously, of our brain's organisational capabilities.

I am a camera

The artist Claude Monet was said to be one, and so is chess champion Bobby Fischer. Mnemonists are people who appear to have total recall; what is sometimes called eidetic, or photographic, memory. S V Shereshevskii, the subject of the book Mind Of A Mnemonist, by A R Luria, could apparently study lists of random words and reel them off decades later. And then there are people who can recite pi to tens of thousands of decimal places, or win large sums at poker by remembering who played what card when.

Very occasionally, people with autism or Asperger's syndrome have spectacular memories; the character in the film Rain Man was based on the "autistic savant" Kim Peek, who has committed around 9,600 entire books to memory. It may be, however, that at least some people who appear to have innate eidetic memories have actually developed an ability to organise information in such a way that it can be readily recalled. Many different techniques exist to achieve this with varying degrees of success - look at the number of newspaper adverts offering to cure, for a price, the embarrassing inability to "put a name to a face". What such techniques aim to do is take advantage of the brain's ability to store not only words and numbers, but also colours, images, sounds, smells, shapes, structures, situations, locations and even emotions, and to group and link these in ways that assist recollection by association.

Colourful imagery

In the Middle Ages, legal settlements such as the positioning of boundary markers were frequently witnessed by children, who were then beaten so that they would, by associating them with the traumatic event, remember the relevant details for the rest of their lives. Fortunately for today's children, mnemonics - the word refers to any memory aid - tend to be verbal. The verse that begins "Thirty days hath September, April, June and November..." is a mnemonic, in that it uses rhyme and metre to render an otherwise unmemorable list of names more memorable. In common parlance, however, the term mnemonic has come to refer to what are properly called acrostics, those catchy phrases whose contents enable us to recall a list of apparently random words by reference to their initial letters. One classic acrostic is "Richard of York gave battle in vain", which fixes the colours of the spectrum - red, orange, yellow, green, blue, indigo and violet - in their correct order.

Rooms for improvement

The handing down of such ready-made memory aids has always been an accepted part of mainstream education. But the passing on of memory techniques which students can use as tools in any situation is a different matter.

Nevertheless, details of techniques used by mnemonists are not only readily available but are also surprisingly easy to master. One of the oldest of these is known as the method of loci. This has been practised since classical times (Cicero names its inventor as Simonides of Ceos, a Greek), and is still the most commonly used by champion mnemonists today. The loci in question are familiar locations or spatial correlations; the houses in your street, say, or the rooms and corridors in your school. If you mentally place the unfamiliar items into these known loci, they can be recalled - in reverse order, or starting at any point in the sequence - simply by referring back to the known sequence. The trick is to bind the unfamiliar with the familiar by way of striking images, and so the more outrageous the sights and sounds conjured up en route, the more easily they will spring to mind later. Quite lengthy lists might be pegged to landmarks on a familiar journey, so long as the exact sequence of familiar loci is established in advance.

The couples game

Two-step memory systems dispense with imagined buildings and journeys altogether, and instead rely on the one piece of knowledge that most of us share, namely the order in which numbers occur. Step one might require the user to memorise a list of consonants which, for the rest of their lives, they will associate with each of the digits 0-9 (for example, 1 might be paired with "t", 2 with "n", and so on). In step two, a user wishing to remember a string of digits can then break the string into manageable sections, each of which translates into a group of consonants, which in turn suggest a word. Remembering a number is then just a matter of building those words into appropriate and easily remembered phrases. A simple, one-step way of remembering a short list of items is to weave them into a memorable story (this is called "chaining"). But a two-step method similar to that used for remembering numbers can enable the user to recall huge lists of words in order. If, instead of being paired with consonants, digits are paired with a pre-learned list of words, then an ordered list of unfamiliar words can be committed to memory simply by mentally pegging each of them in turn to the equivalent word in the familiar list of numbered words (striking images are again called for here). In this way, anyone who has made the effort to learn a list of, say, 100 word-number pairs, can easily remember a list of 100 random words in their correct order.

Lost in translation

Fewer academic exercises require more in the way of straightforward memory than learning an entirely new vocabulary. But once again, many find the principle of pegging a list of unknown items (foreign words) to a list of known items (words in one's mother tongue that happen to sound similar) more reliable than the traditional method of repetition. The key, as always, is to bind the two words together with a memorable, even ludicrous, image; that is, one which draws on a variety of sensory concepts (thinking of a Saab car stuck in the sand, for example, might help a student remember that the French for sand is sable). This is particularly useful when it comes to remembering the gender of words, since there often appears to be no rhyme or reason to the attribution.

The LinkWord system, invented by Michael Gruneberg, uses this principle to teach languages. Gruneberg believes that 1,000 words are all that is needed to get by in most languages, and he claims that an English speaker should be able to learn this number of German words in just 10 hours by using his pairing technique. More elaborate language learning systems combine such word association with the method of loci, distributing pairs of words around a familiar town (adjectives in the park, verbs in the sports centre, and so on) and even dividing the town into two or three separate gender zones.

Mapping and webs

In the 3rd century, Porphyry of Tyros employed graphics to illustrate the arguments of Aristotle, and this use of diagrams with coloured lines, words and images to show how concepts are linked has been in use ever since. From the 1960s, pioneering research into semantic memory and artificial intelligence by the American scientist Dr Allan Collins led to the development of a graphic technique called a concept map or web, which could be used by students as a learning aid. A proprietary system known as Mind Mapping was subsequently developed by Tony Buzan, a British popular psychology writer, and this became the basis of a range of teaching materials, from books to computer software, widely marketed (and strictly trade-marked) by the Buzan Organisation.

Buzan's graphics comprise a central, multi-coloured image of the topic in question, from which organic coloured branches of varying thickness radiate outwards, linking subordinate concepts, all of which are labelled and coloured in ways designed to maximise their memorability. As with most other mnemonics, striking images and imaginative links are used throughout.

As a means of note-taking and committing information to memory, it is claimed that Mind Mapping is vastly superior to traditional linear methods since it echoes the way that the brain is thought to function.

Not everyone is convinced that this is the case, however. Certainly, experience has shown that such systems appeal more to students who have achieved less success with traditional methods, including so-called "visual learners". And at least one study has suggested that many people are better able to retain information if they focus on content rather than the method of note-taking. Arguably, the availability of artificial memory aids such as miniature computers will soon relieve all of us from the need to memorise information, in the same way as calculators have already removed much of the drudgery from mathematics. Only then will the human brain be free to do what it does best: think.


* Visit www.onesmartclick.comexamsimprove-memory.html for an online mnemonic tutorial.

* A compendium of memory tests, experiments and exercises can be found at www.sense-think-act.orgindex.php?title=memory.

* For a succinct description of how memories are formed, visit http:brain.web-us.commemoryhuman_ memory.htm.

* For Buzan products and information, go to Free software can be downloaded at http:freemind.sourceforge.netwikiindex.php Main_Page. has direct links to these websites Main text: David NewnhamIllustration: Mick BrownfieldAdditional research: Sarah Jenkins Next week: Counselling

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