Featured Research

from universities, journals, and other organizations

Study Shows Humans Have Ability To Track Odors, Much Like Bloodhounds

August 30, 2005
University of California - Berkeley
Neuroscientists imaging the brain have confirmed a 40-year-old claim that humans have an untapped ability to localize odors in the same way we localize sounds. In fact, the brain seems to use the same brain region used by the ears to translate input from the two nostrils into spatial information. Someday, humans may vie with dogs and pigs in the ability to track smells.

Jess Porter, a biophysics graduate student, adjusts a mask that will deliver odors to her nose while she lies still in a functional magnetic resonance machine.
Credit: Photo s by Steve McConnell/UC Berkeley NewsCenter

Related Articles

Student volunteers presented with odors to one nostrilor the other could reliably discern where the odor was coming from, andfunctional magnetic resonance images of their brains showed that thebrain is set up to pay attention to the difference between what theleft and right nostrils sense, much the way it can localize sounds bycontrasting input from the ears.

"It has been very controversialwhether humans can do egocentric localization, that is, keep their headmotionless and say where the spatial source of an odor is," said studycoauthor Noam Sobel, associate professor of psychology at UC Berkeleyand a member of the campus's Helen Wills Neuroscience Institute. "Itseems that we have this ability and that, with practice, you couldbecome really good at it."

In future experiments, UC Berkeleybiophysics graduate student Jess Porter and Sobel plan to trainvolunteers to track odors in the field and test the limits of odorlocalization in humans.

Porter, Sobel and their colleagues reported the results in the August 18 issue of the journal Neuron.

Ina review appearing in the same issue of the journal, Jay A. Gottfriedof the Department of Neurology at Northwestern University's FeinbergSchool of Medicine noted that the UC Berkeley findings open numerousavenues for further research. "Finally, what are the implications forthe Provençal truffle hunt?" he wrote, only partly tongue-in-cheek. "Inthe traditional world of the truffle forests, the dog (or pig) is king.The evidence presented here suggests that humans are every bit as wellequipped to carry out the search."

Forty years ago, Nobel Prizelaureate Georg von Békésy claimed that humans had the ability tolocalize odors, based on experiments in 1964 with human subjects. Hesuggested this was done the same way we locate sounds: by contrastingeither the intensity of the odor or the time of arrival.

Sincethen, however, scientists have had difficulty replicating hisexperiments, according to Sobel. One explanation for this failure wasthat von Békésy used chemicals that stimulate not only the olfactorynerve in the nose, but also a nasal sensory nerve, the trigeminalnerve. Most odors stimulate both, and some, like onions and ammonia,are stinging enough to bring tears to the eyes. Perhaps, somesuggested, von Békésy's subjects were localizing odors based ontrigeminal nerve stimulation, not olfactory nerve stimulation.

Toeliminate this confusion, Porter and Sobel used two odors with minimaltrigeminal stimulation - essence of rose (phenyl ethyl alcohol) andcloves (eugenol) - as well as two trigeminal odorants - propionic acid,which smells like vinegar, and amyl acetate, which smells like banana.They delivered the odors through a specially designed mask with anartificial septum that provided separate air flow to each nostril.

Inaddition, they conducted similar experiments on five volunteers who hadno olfactory nerves and therefore couldn't smell at all, a conditionknown as anosmia.

Normal subjects, 16 in all, were able to tellwhich nostril was receiving a squirt of scent, but anosmic volunteerscould only localize the trigeminal odorants, Sobel said. This showsthat humans are able to localize odors through the olfactory nervesalone.

"One possible objection is that the experimental set-up,with a mask that provides separate air flow to each nostril, isartificial. How behaviorally relevant is that?" said Porter. Subsequentexperiments not yet reported, however, provide additional support fortheir hypothesis that the ability to localize odors to one nostril orthe other is realistic.

The experiments were conducted with thesubjects' heads inside a functional MRI to allow the scientists to seewhich areas of the brain were most active during sniffing and attemptsto identify and localize odors. They found that the left and rightnostrils have separate areas of the primary olfactory cortex - thebrain's smell center - devoted to them, indicating that the brain atleast encodes information that could help it localize an odor. Asuccessful detection of an odor is accompanied by more activity in theregion of the olfactory cortex associated with the particular nostril.

"Whilea subject was doing this task, I could look at the brain and tell youhow accurate he or she would be on every trial and on the taskoverall," Sobel said. "So the fact that we have this predictive valuein the data really suggests that we have actually successfully capturedthe mechanism."

What's more, another area of the brain outsidethe olfactory cortex was very active during successful localization.This area, the superior temporal gyrus, is also involved in thelocalization of sounds and visual objects, Sobel said.

"It'sactually a very nice and elegant convergence of this area, the superiortemporal gyrus, that appears to transform non-spatial information intospatial information," he said. "Together, these results are the firstdescription of the mammalian brain mechanisms for extracting spatialinformation from smell."

One key difference between theirexperiment and previous experiments to replicate the results of vonBékésy is that Porter and Sobel asked their subjects to actively sniff,whereas many previous experiments prevented subjects from sniffing.

"Wethink that most people failed to replicate his results for that reason,that is, the extent to which they enabled natural behavior,specifically sniffing," Sobel said. "In some studies subjects asked tolocalize an odor wouldn't be allowed to sniff. That's almost likestudying auditory localization but having your ears plugged. Weactually enabled natural behavior, we enabled subjects to sniff, and wethink that's a major difference."

In addition to Porter andSobel, other authors of the Neuron paper were UC Berkeley seniorscientist Rehan M. Khan of the Department of Psychology and graduatestudents Tarini Anand and Brad Johnson of the Department ofBioengineering. The work was supported by grants from the NationalInstitutes of Health.

Story Source:

The above story is based on materials provided by University of California - Berkeley. Note: Materials may be edited for content and length.

Cite This Page:

University of California - Berkeley. "Study Shows Humans Have Ability To Track Odors, Much Like Bloodhounds." ScienceDaily. ScienceDaily, 30 August 2005. <www.sciencedaily.com/releases/2005/08/050830070723.htm>.
University of California - Berkeley. (2005, August 30). Study Shows Humans Have Ability To Track Odors, Much Like Bloodhounds. ScienceDaily. Retrieved March 30, 2015 from www.sciencedaily.com/releases/2005/08/050830070723.htm
University of California - Berkeley. "Study Shows Humans Have Ability To Track Odors, Much Like Bloodhounds." ScienceDaily. www.sciencedaily.com/releases/2005/08/050830070723.htm (accessed March 30, 2015).

Share This

More From ScienceDaily

More Mind & Brain News

Monday, March 30, 2015

Featured Research

from universities, journals, and other organizations

Featured Videos

from AP, Reuters, AFP, and other news services

AAA: Distracted Driving a Serious Teen Problem

AAA: Distracted Driving a Serious Teen Problem

AP (Mar. 25, 2015) — While distracted driving is not a new problem for teens, new research from the AAA Foundation for Traffic Safety says it&apos;s much more serious than previously thought. (March 25) Video provided by AP
Powered by NewsLook.com
Smartphone Use Changing Our Brain and Thumb Interaction, Say Researchers

Smartphone Use Changing Our Brain and Thumb Interaction, Say Researchers

Reuters - Innovations Video Online (Mar. 25, 2015) — European researchers say our smartphone use offers scientists an ideal testing ground for human brain plasticity. Dr Ako Ghosh&apos;s team discovered that the brains and thumbs of smartphone users interact differently from those who use old-fashioned handsets. Jim Drury went to meet him. Video provided by Reuters
Powered by NewsLook.com
Many Don't Know They Have Alzheimer's, But Their Doctors Do

Many Don't Know They Have Alzheimer's, But Their Doctors Do

Newsy (Mar. 24, 2015) — According to a new study by the Alzheimer&apos;s Association, more than half of those who have the degenerative brain disease aren&apos;t told by their doctors. Video provided by Newsy
Powered by NewsLook.com
A Quick 45-Minute Nap Can Improve Your Memory

A Quick 45-Minute Nap Can Improve Your Memory

Newsy (Mar. 23, 2015) — Researchers found those who napped for 45 minutes to an hour before being tested on information recalled it five times better than those who didn&apos;t. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.


Breaking News:

Strange & Offbeat Stories


Health & Medicine

Mind & Brain

Living & Well

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News


Free Subscriptions

Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile

Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?

Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins