The nose: gateway to memories
Scientists finding direct links between smell, brain and its emotions
By ALEXANDRA WITZE / The Dallas Morning News

You're probably paying more attention to this 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
mustiness of an old trunk, the pungency of a driftwood campfire.

Specific odors can trigger a flood of memories. 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 cookie into a cup of tea – and the scent
and taste unleash a torrent of childhood memories for 3,000 pages.

Now, this phenomenon is getting the scientific treatment.
Neuroscientists have discovered, for instance, how sensory memories
are shared across the brain, with different brain 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, odor 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 odors and the amygdala may help explain the
emotional potency of smells, scientists say.

"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, R.I.

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

In recent experiments, neuroscientists at University College London
asked 15 volunteers to look at pictures while smelling unrelated
odors. 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 scientists reported recently in Neuron.

The fact that the olfactory cortex became active in the absence of
the odor suggests that people's sensory memory of events is spread
across different brain regions, says the University College London
team leader, Jay Gottfried.

Imagine going on a seaside holiday, he says. 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 a third place.

There could be advantages to having memories spread around the
brain. "You can reawaken that memory from any one of the sensory
triggers," says Dr. Gottfried, "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.

A sniff of perfume
Remembered smells may also carry extra emotional baggage, says
Brown's Dr. Herz. Her years of research suggest that memories
triggered by odors are more emotional than memories triggered by
other cues.

In one recent study, Dr. Herz recruited five volunteers who had vivid
memories associated with a particular perfume, such as Opium for
Women and Juniper Breeze from Bath and Body Works. 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. Dr. 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 she 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. Each person then rated how
well the various cues triggered their memory.

Memories triggered by the smell were more evocative than memories
triggered by either sights or sounds, Dr. Herz reported this spring
in the journal Chemical Senses.

More details
Odor-evoked memories may be not only more emotional, but more
detailed as well, a pair of British psychologists has argued in a
series of papers.

Working with colleague John Downes, psychologist Simon Chu of the
University of Liverpool started researching odor and memory partly
because of his grandmother's stories about Chinese culture. As
generations gathered to share oral histories, she said, 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," says Dr. Chu.

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

Element of surprise
Despite such studies, not everyone is convinced that Proust can be
scientifically analyzed. In the June issue of Chemical Senses, Drs.
Chu and Downes exchanged critiques with renowned perfumer and chemist
J. Stephan Jellinek.

Dr. Jellinek chided the Liverpool researchers for, among other
things, presenting the smells and asking the volunteers to think of
memories, rather than seeing what memories were spontaneously evoked
by the odors. But there's only so much science can do to test a
phenomenon that's inherently different for each person, Dr. Chu
responds.

In the meantime, Dr. Jellinek has also been collecting anecdotal
accounts of Proustian experiences, hoping to find some common links
between the experiences.

"I think there is a case to be made that surprise may be a major
aspect of the Proust phenomenon," he says. "That's why people are so
struck by these memories."

No one knows whether Proust himself ever experienced such a
transcendental moment. But his notions of memory, written as fiction
nearly a century ago, continue to inspire scientists of today.

E-mail awitze@...

RESOURCES

The Sense of Smell Institute is at www.senseofsmell.org

A Society for Neuroscience backgrounder on smell and the brain can be
found at
http://apu.sfn.org/content/Publications/BrainBriefings/smell.html

A new English translation of Swann's Way, the first volume of Marcel
Proust's In Search of Lost Time (also known as Remembrance of Things
Past), is available from Viking