WRITER: BECKY SOGLIN
CONTACT: DAVE PEDERSEN
Iowa City IA 52242
(319) 335-8032; fax (319) 384-4638
Release: July 25, 2001
UI researchers find link between altered sense of smell and schizophrenia
IOWA CITY, Iowa -- Enjoying good smells or avoiding bad ones is one of the
most basic human drives. However, people who have schizophrenia have difficulty
recognizing good smells even though they experience bad smells to a similar
degree as healthy people do, according to an investigation involving University
of Iowa Health Care researchers.
In addition, the team found that the brains of people with schizophrenia
work completely differently when it comes to smelling odors, good or bad,
compared to the brain functioning of healthy volunteers. The findings will
appear in the July 25 issue of the Journal of the American Medical Association.
While previous studies have looked at cognitive functions, such as memory
and attention, of people with schizophrenia, this investigation is believed
to be the first study to use neuroimaging techniques to look at anhedonia,
or how people with schizophrenia are impaired in their ability to experience
pleasure and express emotion, said Nancy C. Andreasen, M.D., Ph.D., the Andrew
H. Woods Chair of Psychiatry at the UI and principal investigator of one of
the grants that funded the study.
"Smell is a very basic drive in combination with appetite and sexual
drive," Andreasen said. "If you want to sell a house, you try to
have a smell of home-baked bread because it makes the home more appealing.
If we want to say something is terrible, we say it 'stinks.'
"We found that people with schizophrenia could not recognize good smells
even though they recognized the bad smells just as healthy volunteers did.
This is consistent with what we see at the clinical level, where people with
schizophrenia have lost the ability to experience pleasure. It also adds more
evidence that schizophrenia is a brain disease that affects connections between
areas of the brain."
The study focused on how 18 people with schizophrenia and 16 healthy volunteers
reacted to good and bad smells, a vanilla odor and an acidic odor, respectively.
The research team directly
measured the participants' brain activity using positron-emission tomography
(PET) while they were smelling the different odors. PET maps brain blood flow
so that researchers can see how blood
moves from one brain region to another depending on the mental activities
a person is performing. The patients and healthy subjects were chosen based
on equivalent smoking histories in order to avoid differences caused by an
impaired sense of smell.
The team found that healthy subjects used a primitive part of the brain called
the limbic system, or the "nose brain," to recognize bad smells.
These same healthy people used a more advanced part of the brain, the frontal
lobe, to recognize good smells. However, people with schizophrenia did not
follow this pattern of using the primitive brain to recognize bad odors and
the higher part of the brain to recognize good or pleasurable odors.
"In a fascinating reversal, people with schizophrenia used the frontal,
or advanced part of the brain, to recognize bad smells," Andreasen said.
"It's as if the frontal region gets hijacked for this evolutionary task
of recognizing bad smells, and the ability of the frontal region to experience
pleasurable smells is lost."
She added, "So people with schizophrenia can recognize bad smells, which
is important for survival. But they pay a price for using their frontal lobe
instead of the more primitive part. They have anhedonia, or the loss of the
ability to experience pleasure."
Andreasen said the research points to how investigators need to do more studies
that bridge the clinical and biological bases of schizophrenia. She said the
findings could have implications for understanding certain behaviors in people
with the condition.
"In this particular case involving the recognition of bad odors, it's
as if the brain were really tuned to recognize danger. It has to be highly
vigilant," she said. "That same mechanism could explain why being
highly tuned to recognize danger might lead people to misperceive an inter-personal
experience or a particular other person as dangerous."
Andreasen emphasized the importance of positron-emission tomography in helping
investigators see which brain areas are activated by a particular task or
which areas have increased blood flow because a certain mental activity is
"PET is a very sensitive technique to determine what brain areas are
involved in thought and feelings," said Andreasen, who recently published
a new book, "Brave New Brain: Conquering Mental Illness in the Era of
the Genome," which includes extensive explanations and illustrations
"An analogy would be to think about how, if you're running, more blood
flows to your legs, but if you've just had lunch, the blood shifts to the
stomach to aid digestion. That process in the brain is more fine-grained,
and PET allows us to see it."
The primary author for the UI-based study was Benedicto Crespo-Facorro, M.D.,
Ph.D., who was a visiting post-doctoral fellow from the Hospital Universitario
Marques de Valdecilla in Santander, Spain. In addition to Andreasen, UI researchers
making up the primary research team included Sergio Paradiso, M.D., Ph.D.,
UI assistant professor of psychiatry, and Daniel S. O'Leary, Ph.D., a research
scientist in psychiatry.
The investigation was supported in part by grants from the UI Mental Health
Clinical Research Center, the National Institute of Mental Health, and the
National Alliance for Research of Schizophrenia and Affective Disorders.
University of Iowa Health Care describes the partnership between the
UI College of Medicine and the UI Hospitals and Clinics and the patient care,
medical education and research programs and services they provide.