Thinking Horsemanship Forum: Smell and Memory

Posted to BnTpics yahoogroup but I also found it on Sydney Morning Herald Online......

Fragrant memories

Date: October 16 2004

The scent of a perfume or the mustiness of an old trunk can trigger powerful
childhood memories, and now we know why, writes Alexandra Witze.

You probably pay more attention to a newspaper with your eyes than with your nose.
But lift the paper to your nostrils and inhale. The smell of newsprint
might carry you back to your childhood, when your parents perused the paper on Sunday
mornings.

Or maybe some other smell takes you back: the scent of your mother's perfume, the
pungency of a driftwood campfire.

Specific odours can spark a flood of reminiscences. Psychologists call it the
"Proustian phenomenon", after French novelist Marcel Proust. Near the beginning
of the masterpiece In Search of Lost Time, Proust's narrator dunks a madeleine cake
into a cup of tea, and the scent and taste unleash a torrent of childhood
memories for 3000 pages.

Now this phenomenon is getting the scientific treatment. Neuroscientists have
discovered, for instance, how sensory memories are shared across the brain,
with different regions remembering the sights, smells, tastes and sounds of a
particular experience.

Meanwhile, psychologists have demonstrated that memories triggered by smells can be
more emotional, as well as more detailed, than memories not related
to smells.

When you inhale, odour molecules set brain cells dancing within a region known as the
amygdala, a part of the brain that helps control emotion. In contrast,
the other senses, such as taste or touch, get routed through other parts of the brain
before reaching the amygdala.

The direct link between odours and the amygdala may help explain the emotional
potency of smells. "There is this unique connection between the sense of
smell and the part of the brain that processes emotion," says Rachel Herz, a
cognitive neuroscientist at Brown University in Providence, Rhode Island.

But the links don't stop there. Like an octopus reaching its tentacles outward, the
memory of smells also affects other brain regions.

In recent experiments neuroscientists at University College London asked 15
volunteers to look at pictures while smelling unrelated odours. For instance,
the subjects might see a photo of a duck paired with the scent of a rose, and then be
asked to create a story linking the two.

Brain scans taken at the time revealed that the volunteers' brains were particularly
active in a region known as the olfactory cortex, which is known to
be involved in processing smells. Five minutes later, the volunteers were shown the
duck photo again, but without the rose smell. And in their brains,
the olfactory cortex lit up again.

The fact that the olfactory cortex became active in the absence of the odour suggests
that people's sensory memory of events is spread across different
brain regions.

Imagine going on a seaside holiday, says research leader Jay Gottfried. The sight of
the waves becomes stored in one area, whereas the crash of the surf
goes elsewhere, and the smell of seaweed in yet another place.

There could be advantages to having memories spread around the brain. "You can
reawaken that memory from any one of the sensory triggers," Gottfried says.
"Maybe the smell of the sun lotion, or a particular sound from that day, or the sight
of a rock formation."

Or, in the case of an early hunter-gatherer out on a plain, the sight of a lion might
be enough to trigger the urge to flee, rather than having to wait
for the sound of its roar and the stench of its hide to kick in as well.

Remembered smells may also carry extra emotional baggage, says Herz. Her research
suggests that memories triggered by odours are more emotional than memories
triggered by other cues.

In one recent study Herz recruited five volunteers who had vivid memories associated
with a particular perfume. She took images of the volunteers' brains
as they sniffed that perfume and an unrelated perfume without knowing which was
which. (They were also shown photos of each perfume bottle.)

Smelling the specified perfume activated the volunteers' brains the most,
particularly in the amygdala, and in a region called the hippocampus, which helps
in memory formation. Herz published the work earlier this year in the journal
Neuropsychologia.

But she couldn't be sure that the other senses wouldn't also elicit a strong
response. So in another study Herz compared smells with sounds and pictures.

She had 70 people describe an emotional memory involving three items: popcorn,
fresh-cut grass and a campfire. Then they compared the items through sights,
sounds and smells. For instance, the person might see a picture of a lawnmower, then
sniff the scent of grass and finally listen to the lawnmower's sound.

Memories triggered by smell were more evocative than memories triggered by either
sights or sounds.

Odour-evoked memories may be not only more emotional, but more detailed as well.
Working with colleague John Downes, psychologist Simon Chu of the University
of Liverpool started researching odour and memory partly because of his grandmother's
stories about Chinese culture.

As generations gathered to share oral histories, they would pass a small pot of spice
or incense around; later, when they wanted to remember the story in
as much detail as possible, they would pass the same smell around again.

"It kind of fits with a lot of anecdotal evidence on how smells can be really good
reminders of past experiences," Chu says.

And scientific research seems to bear out the anecdotes. In one experiment Chu and
Downes asked 42 volunteers to tell a life story, then tested to see whether
odours such as coffee and cinnamon could help them remember more details in the
story. They could.

On the scent

* Everyone has his or her unique odour identity or smell fingerprint.

* No two people smell the same odour the same way - a rose may smell sweeter to some.

* The average human is able to recognise about 10,000 different odours.

* Our sense of taste is greatly influenced by our sense of smell.

* Your sense of smell is least acute in the morning.

* Dogs have about 200 million olfactory receptors - 20 times the number for humans.

Smell and Memory

Finally!