Researchers in a study published in the Aug. 18 issue of Neuron present the first clear evidence that the brain processes the same odorant molecule differently if it arrives through the nose rather than the mouth.
Dana Small, assistant professor in the Department of Surgery at the School of Medicine and the John B. Pierce Laboratory, says she and her colleagues investigated whether sensing an odor "orthonasally," or through the nose, produces similar brain response as sensing it through the mouth, or "retronasally."
"When we sense an odor retronasally we perceive it as coming from the mouth," says Small. "We may say that we like the 'taste' of a wine because of its fruity or spicy notes. However, gustation refers only to the sensations of sweet, sour, salty, savory and bitter. The pleasant 'taste' to which we refer is actually a pleasant odor sensed retronasally (through the mouth) and misattributed to taste because it is perceived to be coming from the mouth."
The researchers were interested in determining if retronasal olfaction is simply an alternate route to the same neural system that is responsible for orothonasal olfaction, or if it evokes unique neural responses. "If the latter is true," says Small, "then we will have evidence of the existence of distinct olfactory subsystems; one specialized for sensing objects at a distance and one for sensing objects in the mouth."
The researchers inserted small tubes into the noses of volunteers so that one tube ended at the nostrils and the other ended farther back in the nasal passage near the throat, where odors from the mouth would originate. As they introduced four odors into one tube or the other -- chocolate for a food odor, lavender as a non-food odor, and two chemical odors, butanol and farnesol -- they scanned the subjects' brains using functional magnetic resonance imaging.
In support of the existence of separate olfactory subsystems, they found that retronasally sensed odors activated the part of the brain that represents the mouth, possibly reflecting the fact that retronasal but not orthonasal odors are perceived as coming from the mouth. They were also intrigued to observe that the greatest effect of route of delivery occurred for the chocolate odor. Since only food-related odors have been previously experienced retronasally, the finding raises the possibility, the researchers say, that the route of odorant administration interacts with experience to engage unique brain regions.
The co-authors were Erica Mak of Yale and Thomas Hummel and Johannes Gerber of the University of Dresden Medical School.
-- By Jacqueline Weaver
T H I S
W E E K ' SS T O R I E S
Yale community extends helping hand to the victims of Hurricane Katrina
Yale leaders contribute $70,000 to match employee and student donations
Student donates prize money to aid victims of hurricane
Panel examined why Katrina was 'a perfect storm' of failure
Brenzel named undergraduate admissions dean
Studies explore function and formation of feathers
Chinese president's visit postponed
ENDOWED PROFESSORSHIPS
Richard L. Cohn: Battell Professor of the Theory of Music
Lawrence Manley: William R. Kenan Jr. Professor of English
Robert S. Nelson: Robert Lehman Professor of the History of Art
Susan C. Stokes: John S. Saden Professor of Political ScienceNBA star to discuss his humanitarian efforts in the Congo
Director Sofia Coppola to give Chubb Lecture
Labor-management training aims to foster cooperation
Project explores how cultural outlook impacts opinions
MEDICAL SCHOOL NEWS
NIH gives $3.6 million for research to alleviate anxiety . . .
Common pesticide linked to reduced fertility in women
Most implanted embryos are not viable, says study
Study: Hormone therapy for menopause leads to fewer wrinkles
Nicotine, long thought to curb appetite, may actually increase it . . .
Research shows brain distinguishes between odors inhaled . . .
Schizophrenics with diabetes still receive antipsychotic drugs . . .
Medical school offering clinical trial of new treatment . . .'Days of Caring'
Event celebrates 400-year anniversary of 'Don Quixote'
Symposium to examine history of U.S. reach into the Pacific
Scientist Pan invited to participate in NAE symposium
Electrical engineer T.P. Ma is honored for solid-state research
In weekly series, World Fellows will debate global topics
University will celebrate Constitution Day on Sept. 20
Multimedia artist presents photo exhibit and video installation at ISM
'A Taste of Bulgaria' to aid flood victims in another corner of the world
Urban infra-power and urban charisma to be explored in conference
Search committee named for School of Art dean
Biophysical chemist Julian Sturtevant . . .
Memorial service scheduled for . . . Robert Abelson
Alumni magazine now reaches every Yale graduate in the U.S.
Campus Notes
Bulletin Home|Visiting on Campus|Calendar of Events|In the News
Bulletin Board|Classified Ads|Search Archives|Deadlines
Bulletin Staff|Public Affairs|News Releases|
E-Mail Us|Yale Home