You Must Remember

Sun Herald

Sunday October 23, 2005

David Astle

They live in the corners of our minds but how do memories form and why are they sometimes so elusive? Does recall fade with age and do elephants never forget? David Astle takes a trip down memory lane.

What did you have for lunch last Tuesday? Unless you choked on a fishbone or went on a blind date with an Olympic swimmer, chances are you can't remember. Not in detail.

You could probably guess, arriving at a vague or "coarse-grain" memory, but nothing a detective could bank on. Your meal is lost in the sands of time, like so many incidentals - from small talk to long movies. Our memory acts as judge of what we keep and what we don't.

Filtering is just one little trick our brains perform, keeping the memory banks clear for the stuff worth keeping (or Monty Python scripts, as the case may be). Cognitive scientists liken short-term memory to a scratch pad, a jotter where we scribble minor details for a moment - some 10 seconds or less - before dispatching the page to oblivion.

That's unless you (or your brain) opt to retain the input for reasons of relevance, interest or random catch-ability (the "stupid song" syndrome).

If so, the pencil jottings will darken. Short term turns to long term via an exquisite neural conduit in the brain's core called the hippocampus (literally a seahorse, thanks to its shape). The lab word for this transfer is consolidation, something dreams could well enhance.

Relax. There won't be a quiz at the end but this story will take a mystery tour through memory: how it works and why it fails. Just as the brain is divided into four lobes, with memory diffused throughout, this article falls into three sections. Or is that four? I've forgotten...

TUNING IN

Egyptians weren't overly enamoured with the brain. To mummify Tut, for one, they first stuck a wire up the pharaoh's nostril and plied his grey matter loose. For them, the heart was the all-important organ.

Across the water, the Greeks awarded the brain a higher office. Democritus, a philosopher around 430 BC, reckoned atoms danced in human skulls and these atoms carried ideas. He wasn't too far wrong. Just swap the word "atoms" for "nerve cells" and the cerebral jig is up.

Professor Martin Conway, a memory expert at the University of Durham in the UK, uses tuning forks to explain how neurons capture memory. Imagine a room with a trillion tuning forks, he told the BBC World Service, each one representing a neuron in your noggin. Along comes a stimulus (a fresh detail) for the brain to process. To demonstrate, the professor banged a fork, setting off a reverb with others in its register...

The initial "noise" equates to consciousness, he said, or the potential of memory. The reverb is association - or binding - where other parts of the brain recognise the new information and consign it to the databank. The richer the connection (remember relevance and interest), the more likely the stimulus will fix in the memory.

Cranial scans on rats and other animals show "neural cascades" where the creatures recall learned stimuli. On cue, electric webs will shoot across the brain, retrieving stored messages, sounds, images or emotions. Importantly, animals highlight the core function of memory - less retrospection than survival. Dogs don't reminisce, for example, but they do recall prompts to follow a scent, say, just as we retain key facts that allow us to find food and warmth and avoid oncoming traffic.

Memory has several modes. Serving a tennis ball is procedural memory. Recalling your last game is episodic. And the rules of tennis? Semantic. Likewise, such modes can be stored across the hemispheres, according to their format (visual, emotional, etc) and function. An image such as that room full of tuning forks may now be part of your parietal lobe - located on either side of the head's crown. Noise, music or spoken instructions are hoarded in the temples - or temporal lobe. Such diffusion is nature's way of protecting memory. If a truncheon strikes our scone, we won't lose everything.

So why does an obsolete phone number stick in the mind but your newsagent's name remains elusive? One reason is chunking. Most of us break long numbers into clusters and make the sequence rhythmic. Aboriginal songlines and ad jingles depend on the same principle.

However, Nick (or Jeff), who sells you papers, is cold prose, so to speak. You've yet to grasp his name in a conscious or multiple way. Or maybe you don't care that much - conscious memory demands focus. But if the same guy were a mate of your brother's, the cue increase would fasten memory and more tuning forks would sing.

NOT ALL THERE

In the 1980s, Mick Jagger accepted a seven-figure advance to write his memoir. Eventually, the rocker returned the loot, saying he couldn't remember anything much to tell. David Bowie, in the same vein, claims he can't recall a single detail of 1975. When asked to count her husbands, Elizabeth Taylor replied, "What is this, a memory test?"

Over time - or wild living - memories can blur. Nathan Weber, a memory researcher at Adelaide's Flinders University, has been studying memory fallibility, especially among eyewitnesses. "If you ask me what time I left work today," he says, "and

I say 6.03 or six-ish or between five and seven, the more informative my answer, the greater the chance it's wrong." For most of us, memory is an educated approximation of what we experience - not a snapshot.

"Grain size comes into memory a lot," says Weber, where "fine grain" describes a vivid recollection and "coarse grain" is Tuesday's lunch. "We use it all the time - seeing a semi-familiar face in the street and measuring our own confidence with a certain memory." Weber calls it social insurance policy, where we sift inbuilt data for surer memory (of a face, a fact, a name, a figure) before blurting the details in public.

Daniel Schachter, psychology professor at Harvard University, has coined the term "creative memory", where the brain freely edits and generalises the neural coding that makes up a memory. Rather than being a snapshot, episodic memory (your last day of school, for example) goes closer to a script-in-workshop, relying on a bunch of familiar props you hold to be true.

We aren't necessarily lying, said Schachter in an interview with the BBC World Service, but grabbing what blocks we can and building with them. Just

as molecules need frequent replacing around the brain's synapses so do we re-slant memory's nuances, depending on what gist we've kept.

Such a dynamic picture might seem to only heighten the chances of false memory entering our mind-set, where even the brilliant child psychologist Jean Piaget can swear fiction to be true. The year was 1900 - Piaget was four. The boy was being wheeled along the Champs Elysees when a stranger tried to seize him. His nurse fought off the attacker and young Jean was safe. He was also deluded because the episode never happened.

The nurse had invented the tale to impress the Piaget parents with her virtues.

Nor are false memories confined to the psych couch. Clinical tests have shown that humans are prone to believing make-believe (a childhood dog attack or an exaggeration) via a subtle stream of positive prompts to support the lie. Repetition and leading questions - each a tack of so-called priming - can also nurture falsehood in the system. Likewise, family yarns and photo albums may see stories drift from imagination into memory.

Repressed memory is a different kettle of neurons. Childhood abuse, say, or battle trauma may lie buried in the brain's emotional vault, known as the amygdala - literally "almond", again for its shape.

"In mental life," wrote Sigmund Freud, "nothing which has once been formed can perish." Actively or subconsciously, we try to smother painful memories. In many cases, a passing prompt (a siren's wail, the molester's aftershave) can revive the memory in disabling ferocity, complete with the emotional toll.

GREYING MATTER

Research psychology student Laura Haynes is focusing on the mental blocks that supposedly afflict the ageing brain. That's the stereotype our senior citizens cop but Haynes's experiments at the University of NSW suggest that memory remains agile and vital in many older people.

"In the past, experiments have asked 70-year-olds to memorise nonsense syllables or a random sequence of digits," she says. "You've got to wonder how their results apply to everyday life." Instead, Haynes arranged her test around "ecological validity", testing aged and younger subjects on two narratives - the first dealing with the September 11 attacks, the other with a wrangle in the Japanese parliament. New York was an episode familiar to all generations. The Japanese story was deliberately unfamiliar. For some participants, the 400-word account was written in simple language. For others, the accounts, although following the same semantic lines, were written in a more elaborate way.

"I wanted to test the prevailing theory that our ability to deal with complexity diminishes as we age." The oldies scored well, on par with the twentysomethings, in the most mentally demanding task. While prospective memory (keeping shopping lists and appointments in mind) can fray among baby boomers, episodic memory seems fit for the distance. "I used to be afraid of growing old," laughs Haynes, who's bound for Cambridge on a neuroscience scholarship, "but I'm not any more."

Leo Tolstoy embodied such optimism. At 67, the Russian writer learned to ride a bike. Queen Victoria, at the age of 78, tackled the gnarly verbs of Hindustani. At 74, Frank Lloyd Wright doodled plans for the Guggenheim Museum. All are testaments to human memory - and more reasons why Haynes can't contain herself.

"Memory's this amazing mystery," she says as she tries to label the nervous jelly we call a brain. "It's a mixture of neuroscience, psychology and maths with chemistry - and it's going to come down to physics at some point. It blows your mind."

TIP-OF-THE-TONGUE moments

Known as TOT in the cognitive trade, these moments derive from a weakened connection between two memory modes - often sound and meaning. Of course, you know that a daytime sleep is a "siesta" but sometimes the semantic can't snappily marry the phonetic in quick time. So you opt for "nap" and skip the mental block. Names, alas, don't allow us the same leeway. Your nephew Josh is only Josh so you mask that "pre-sneeze feel" of groping in the memory banks, waiting for the wiring to fire. In Ancient Rome, the rich relied on a "nomenclator", a slave whose task was to provide the names of all those in the forum. Now that's thinking.

JUMBO MEMORY

Squirrels are just as sharp as elephants in the memory stakes. While a captive jumbo can retain more than 20 commands, a squirrel can zero in on 5000 buried nuts over winter. The feat, scientists discovered, was a tribute to recall, not smell. Human memorists are almost as impressive. In 2003, England's Andi Bell memorised 89 shuffled decks of cards in five hours. His technique was association, linking each card to an animal, object or character. Seven of Hearts was, naturally, James Bond

- the 007 heart-throb - and so on.

Second time around

Let's say you fly to Cairo on your first trip to Egypt. You touch down and somehow think you've been to the airport before. This is due to: (a) airports being the same the world over; or (b) a memory glitch called deja vu - literally "already seen".

Our brains can usually distinguish between a new memory and the recall of the memory itself. The exception, it's believed, is when the two processes - storage and access - misfire. The present ("I'm landing") is confused with the past ("Been there, done that"). Such eeriness can make you check your passport to see if maybe, just maybe, you lived by the Nile in a past life.

© 2005 Sun Herald

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