Name that smell—if you can't, it could be an indicator of a problem somewhere in your brain. New research suggests that scratch-and-sniff smell tests could become an easy and cheap way to detect signs of traumatic brain injury and neurodegenerative ailments. Recent research found that a diminished sense of smell predicted frontal lobe damage in 231 soldiers who had suffered blast-related injuries on the battlefield. In the Department of Defense study led by Michael Xydakis of the Uniformed Services University of the Health Sciences, subjects with low scores on a smell test were three times as likely to show evidence of frontal lobe damage during brain imaging than those whose sense of smell was normal. When the sense of smell is working properly, it acts as a matchmaker between odorant molecules in the air and memories stored in the brain. Those memories are not housed in a single place, Xydakis says, but extend across many regions. Because different smell signals have to take a variety of paths to reach their destinations, arranging their travel requires a lot of coordination. “This unique feature makes an individual's ability to describe and verbally name an odor extremely challenging and cognitively demanding,” he says. A damaged sense of smell, therefore, can indicate that the ability to make those connections has been hampered by disease, a lack of sleep or, as shown in Xydakis's study, injury to the brain. The new results add to a growing understanding of the link between brain damage and an impaired sense of smell. Researchers have been working for years to use olfaction tests to track damage to the brain caused by neurodegenerative ailments such as Parkinson's and Alzheimer's diseases. Kim Good, an associate professor in the psychiatry department at Dalhousie University in Nova Scotia, is currently recruiting subjects for a cohort study that aims to better understand the link between olfaction and Parkinson's, which could improve early identification and intervention. “Olfactory deficits are as common as tremor in Parkinson's, and they help rule out other competing diagnoses,” Good says. Smell is also the first sense to be affected by Alzheimer's, with the hallmark protein tangles of the disease appearing early in the olfactory bulb, says psychiatrist Davangere Devanand of Columbia University. Last January he and his colleagues reported the results of a four-year-long cohort study in Manhattan, which found that scores on a multiple-choice scratch-and-sniff test in which participants had to identify 40 scents were good predictors of cognitive decline. It's not hard to imagine such exams becoming a routine part of primary care for older patients. “The beauty of olfaction,” Good points out, “is that testing is easy and can be done in the family physician's office.” — Ian Chant Why Smell Is Special The unique characteristics of our sense of smell make sniff tests ideal for diagnosing brain injury. Here are some of the most interesting scientific findings about this unusual sense: —Victoria Stern Ian Chant Recent Articles Forgetting Is Harder for Older Brains Could a Neural Implant Correct Errant Thoughts? How to Intentionally Forget a Memory Victoria Stern Recent Articles Mass Shootings Are Contagious Three Books Explore the Inner World of Animals Three Books Explore the Spiral of Shame ADVERTISEMENT The adult brain can generate new neurons in the olfactory bulb, the brain region that processes smells. This area is one of just a few regions that continue to grow new neurons during adulthood. Individuals vary in how they perceive odors and whether or not they can detect certain scents, and yet humans seem to universally enjoy the smell of vanilla. Anosmia, a condition in which people completely lose their sense of smell, can be debilitating. Sufferers often report feeling disconnected from their surroundings, and many become severely depressed. Romantic couples can unconsciously sense their partner's emotional state from their sweat—and the longer they have lived together, the better they are at it. Babies locate their mother's nipples in part by learning a smell map of the breasts.

Memory for odors is particularly
complex, making scratch-n-sniff
tests an early indicator of damage
to the brain

Name that smell—if you can't, it
could be an indicator of a
problem somewhere in your
brain. New research suggests that
scratch-and-sniff smell tests could
become an easy and cheap way to
detect signs of traumatic brain
injury and neurodegenerative
ailments.
Recent research found that a
diminished sense of smell
predicted frontal lobe damage in
231 soldiers who had suffered
blast-related injuries on the
battlefield. In the Department of
Defense study led by Michael
Xydakis of the Uniformed Services
University of the Health Sciences,
subjects with low scores on a smell
test were three times as likely to
show evidence of frontal lobe
damage during brain imaging
than those whose sense of smell
was normal.
When the sense of smell is
working properly, it acts as a
matchmaker between odorant
molecules in the air and memories
stored in the brain. Those
memories are not housed in a
single place, Xydakis says, but
extend across many regions.
Because different smell signals
have to take a variety of paths to
reach their destinations,
arranging their travel requires a
lot of coordination. “This unique
feature makes an individual's
ability to describe and verbally
name an odor extremely
challenging and cognitively
demanding,” he says.
A damaged sense of smell,
therefore, can indicate that the
ability to make those connections
has been hampered by disease, a
lack of sleep or, as shown in
Xydakis's study, injury to the
brain. The new results add to a
growing understanding of the link
between brain damage and an
impaired sense of smell.
Researchers have been working
for years to use olfaction tests to
track damage to the brain caused
by neurodegenerative ailments
such as Parkinson's and
Alzheimer's diseases.
Kim Good, an associate professor
in the psychiatry department at
Dalhousie University in Nova
Scotia, is currently recruiting
subjects for a cohort study that
aims to better understand the link
between olfaction and
Parkinson's, which could improve
early identification and
intervention. “Olfactory deficits
are as common as tremor in
Parkinson's, and they help rule
out other competing diagnoses,”
Good says.
Smell is also the first sense to be
affected by Alzheimer's, with the
hallmark protein tangles of the
disease appearing early in the
olfactory bulb, says psychiatrist
Davangere Devanand of Columbia
University. Last January he and
his colleagues reported the results
of a four-year-long cohort study in
Manhattan, which found that
scores on a multiple-choice
scratch-and-sniff test in which
participants had to identify 40
scents were good predictors of
cognitive decline.
It's not hard to imagine such
exams becoming a routine part of
primary care for older patients.
“The beauty of olfaction,” Good
points out, “is that testing is easy
and can be done in the family
physician's office.” — Ian Chant
Why Smell Is Special
The unique characteristics of our
sense of smell make sniff tests
ideal for diagnosing brain injury.
Here are some of the most
interesting scientific findings
about this unusual sense:
—Victoria Stern
Ian Chant
Recent Articles
Forgetting Is Harder for Older Brains
Could a Neural Implant Correct Errant
Thoughts?
How to Intentionally Forget a Memory
Victoria Stern
Recent Articles
Mass Shootings Are Contagious
Three Books Explore the Inner World of
Animals
Three Books Explore the Spiral of Shame
ADVERTISEMENT
The adult brain can generate
new neurons in the olfactory
bulb, the brain region that
processes smells. This area is
one of just a few regions that
continue to grow new neurons
during adulthood.
Individuals vary in how they
perceive odors and whether or
not they can detect certain
scents, and yet humans seem to
universally enjoy the smell of
vanilla.
Anosmia, a condition in which
people completely lose their
sense of smell, can be
debilitating. Sufferers often
report feeling disconnected
from their surroundings, and
many become severely
depressed.
Romantic couples can
unconsciously sense their
partner's emotional state from
their sweat—and the longer
they have lived together, the
better they are at it.
Babies locate their mother's
nipples in part by learning a
smell map of the breasts.