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Emotional Disorder Is Linked to Smell
By ERICA GOODE , (N.Y. Times)
The sense of smell, as Marcel Proust
and his madeleine made clear, is
intimately tied to feeling and memory.
So it is perhaps not surprising that in
schizophrenia, an illness that plays havoc
with the emotional capacities of those who
suffer from it, the sense of smell is impaired.
People with schizophrenia often display what
psychiatrists describe as a "blunting" of
emotional response that makes it difficult for
them to relate to others. But they also,
researchers have found, show deficits in their ability to
detect, identify and
remember odors.
Now a new study, appearing in this month's American Journal of
Psychiatry, suggests that these abnormalities in the sense of
smell have
their root in abnormal brain structure.
Using magnetic resonance imaging, Dr. Bruce Turetsky, an
associate
professor of psychiatry at the University of Pennsylvania, and
his
colleagues examined the olfactory bulbs -- blueberry-sized
organs that act
as relay stations between the nose and brain -- in 26
schizophrenic patients
and 22 comparison subjects.
The bulbs of patients with schizophrenia, the researchers
found, were on
average 23 percent smaller in volume than those of control
subjects.
The discrepancy in size, said Dr. Turetsky, was large enough
that it was
clearly visible on the M.R.I. scans. And the difference
between the groups
persisted even after cigarette smoking, the use of
anti-psychotic
medications, age and other factors that might influence the
size of the bulbs
were taken into account.
The study, said Dr. Robert Bilder, associate director for
human research at
the Center for Advanced Brain Imaging of the Nathan Kline
Institute for
Psychiatric Research in Orangeburg, N.Y., is the first to
reveal, in
schizophrenia, a structural abnormality in more primitive
brain areas, which
are also involved in emotional processing.
"For the last 10 or 20 years," Dr. Bilder said, schizophrenia
researchers
have paid "an enormous amount of attention to the higher parts
of the brain
and the associated higher cognitive functions. This kind of a
study is
important in moving the focus to lower brain systems, that are
crucial to
the regulation of emotion and visceral functions."
Further investigation of the relationship between olfaction
and
schizophrenia, Dr. Turetsky said, may also help shed light on
the emotional
disturbances that are characteristic of the illness.
"Smell is so tightly linked to emotional processing," Dr.
Turetsky said. "It's
essentially impossible to present an olfactory stimulus that
doesn't have an
emotional valence to it."
The olfactory system offers scientists a unique window on both
normal and
abnormal brain functioning, in part because it is so clearly
laid out, with
sensory impulses traveling from receptors in the nose to the
olfactory
bulbs, where they are decoded, and then to olfactory centers
in higher
brain regions.
And the changes in olfaction observed in
schizophrenia, researchers believe, may
also
contain clues to how the disease
develops.
Many scientists suspect that
schizophrenia is
a neurodevelopmental disorder, a result
of
hereditary predisposition and some
environmental insult, perhaps occurring
during the early months of fetal growth.
Whether the smaller size of the
olfactory
bulbs in schizophrenia reflects abnormalities occurring early
in development
or stems from a degenerative process later in life is still
unknown, Dr.
Turetsky said. But, he pointed out, olfactory neurons, unlike
those in other
areas of the brain, die and are replaced throughout life,
displayinga
plasticity that makes the olfactory system relatively
resistant to
degenerative disease.
A loss of smell or abnormalities in odor identification or
detection is also
seen in some degenerative diseases, like Alzheimer's. The next
task facing
the researchers, said Dr. John Q. Trojanowski, a professor of
pathology
and laboratory medicine at Penn, is to show that the smaller
volume of the
olfactory bulbs is specific to schizophrenia and is not found
in other
illnesses, like manic depression, alcoholism or dementia.
Although scientist have been studying the brains of patients
with
schizophrenia for a century or more, no one appears to have
ever noticed a
difference in the size of the olfactory bulbs.
One reason, Dr. Trojanowski said, may be that early
researchers saw no
particular reason to pay attention.
"If you look at how the bulbs sit in the skull when you take
out the brain,
it's easy to leave them behind," Dr. Trojanowski said.
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Cheers ,
Joao Paulo - Salvador,BA,Brazil
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