Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

How the nose knows a rose - or a mate

14.02.2003


If you sniff a rose this Valentine’s Day, your brain will recognize almost a hundred different molecules that collectively give the flower its heady scent-but how? Scientists are now discovering how the brain identifies odors and their mysterious counterparts, the pheromones. New research, to be presented today at the American Association for the Advancement of Science (AAAS) Annual Meeting and forthcoming in the journal, Science, explains how the mouse brain is exquisitely tuned to recognize another mouse’s pheromone cocktail.



Researchers say that most smells hover about 10 inches off the ground, placing the human nose at a disadvantage among those of most other mammals. Nonetheless, when smells do reach the neurons inside the nose, the human brain can distinguish from among the thousands of chemicals that make up odors, and scientists are beginning to understand just how the process works.

In the last decade, the nose has been revealed as the site of a large family of sensory neurons, each of which specializes in a particular smell. Since this discovery, researchers have studied the olfactory system in rodents, following the axons that extend from neurons into the rodent brain. Their research shows that the axons from neurons with receptors for the same odor molecule congregate in the one or two glomeruli that are reserved for those axons. Glomeruli, which contain only axon terminals, are specialized structures in the olfactory bulb; the rodent brain has 2000 of them. By studying "odor maps" that show activity in certain glomeruli in response to different smells, Howard Hughes Medical Institute investigator Lawrence C. Katz of Duke University has found that each odor results in a pattern or "fingerprint," which humans and other mammals seem to use to distinguish from among different smells.


"We needed a way to ’see’ which specific glomeruli were activated by different odorants," said Katz, a professor of neurobiology at Duke. "We accomplished this by using a technique called ’optical imaging of intrinsic signals,’ which allowed us to take a picture of the bulb when it was being stimulated by a particular odor, and when it wasn’t."

While the human brain’s ability to distinguish different odors may be impressive, many mammalian brains can also identify an altogether different type of "smell." Mammals ranging from mice to elephants produce substances called pheromones, which communicate information about social status and when an individual is ready to reproduce. These signals are somehow picked up through the "accessory" olfactory system, which is separate from the "main" olfactory system that allows us to appreciate, for example, the scent of a rose bouquet.

Scientists have understood little about the accessory olfactory system, but a new mouse study by Katz and his colleagues, forthcoming in Science, should change that. It reveals that pheromone-detecting neurons in this system are carefully "tuned" to pick up on another mouse’s sex and genetic makeup. This type of smelling may thus be a handy way for certain mammals to identify potential mates (and may also help mice get around the fact that they look pretty much alike). These findings may also open the way to a better understanding of how animals communicate dominance, mating receptivity, and individuality, according to Katz and his coauthors. The researchers implanted three microelectrodes into a specific region of the mouse’s brain where they would record the activity of individual neurons responding to different pheromones. Then they added to the cage a second mouse, which was lightly anaesthetized, so that the test mouse could get close for a sniff. The test mouse’s neurons each had highly selective responses to the pheromones of the introduced mouse, depending on the introduced mouse’s genetic strain and sex. Interestingly, the face seemed to be the most important source of pheromones.

Other researchers are exploring how the axons from the sensory neurons negotiate "an extremely hostile environment" to make their way into the brain, according to Charles Greer, professor of neuroscience in the Department of Neurosurgery and Section of Neurobiology at Yale University School of Medicine. He points out that unlike the axons of any other neurons, axons from the sensory neurons travel in bundles that are wrapped in tentacle-like glial processes, offering a possible model for encouraging the growth of neurons in areas that have been damaged following spinal cord injury. "Think of the glial cells as a person with their arms wrapped around the axons," Greer said. "We’ve taken these glial cells, and have begun to make spinal cord cells functionally enervate areas."

During the AAAS Annual Meeting, a panel on olfactory research also will explore the question of "olfactory memories"-how the brain can retain memories of smells, despite rapid turnover in the sensory neurons that inhabit the nose. Katz notes that the one of the next breakthroughs in the science of the olfactory system will allow scientists "to unravel the links between olfactory perception and the formation of long-term olfactory memories."

Advance interviews possible upon request.

The American Association for the Advancement of Science (AAAS) is the world’s largest general scientific society, and publisher of the journal, Science. Founded in 1848, AAAS serves 134,000 members as well as 272 affiliates, representing 10 million scientists.

For more information on the AAAS, see the web site, www.aaas.org. Additional news from the AAAS Annual Meeting may be found online at www.eurekalert.org.

MEDIA NOTE: Katz will take part in a newsbriefing during the AAAS Annual Meeting in Denver on Thursday, 13 February at 12:00 p.m. noon Mountain Time, Rooms C-110-112, in the Colorado Convention Center. Katz , Greer and other researchers will then participate in an Annual Meeting session titled, "How the Nose Knows: Neural Circuits for Chemical Detection," at 2:30 p.m. Mountain Time, Saturday, 15 February, in Room A-205 on the Main Level of the Colorado Convention Center. Reporters must register at the AAAS Press Center, Rooms C-101-103, Colorado Convention Center.


AAAS is the world’s largest general scientific society, dedicated to "Advancing science • Serving society."

Monica Amarelo | EurekAlert!
Further information:
http://www.aaas.org/

More articles from Life Sciences:

nachricht Cancer diagnosis: no more needles?
25.05.2018 | Christian-Albrechts-Universität zu Kiel

nachricht Less is more? Gene switch for healthy aging found
25.05.2018 | Leibniz-Institut für Alternsforschung - Fritz-Lipmann-Institut e.V. (FLI)

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Powerful IT security for the car of the future – research alliance develops new approaches

The more electronics steer, accelerate and brake cars, the more important it is to protect them against cyber-attacks. That is why 15 partners from industry and academia will work together over the next three years on new approaches to IT security in self-driving cars. The joint project goes by the name Security For Connected, Autonomous Cars (SecForCARs) and has funding of €7.2 million from the German Federal Ministry of Education and Research. Infineon is leading the project.

Vehicles already offer diverse communication interfaces and more and more automated functions, such as distance and lane-keeping assist systems. At the same...

Im Focus: Molecular switch will facilitate the development of pioneering electro-optical devices

A research team led by physicists at the Technical University of Munich (TUM) has developed molecular nanoswitches that can be toggled between two structurally different states using an applied voltage. They can serve as the basis for a pioneering class of devices that could replace silicon-based components with organic molecules.

The development of new electronic technologies drives the incessant reduction of functional component sizes. In the context of an international collaborative...

Im Focus: LZH showcases laser material processing of tomorrow at the LASYS 2018

At the LASYS 2018, from June 5th to 7th, the Laser Zentrum Hannover e.V. (LZH) will be showcasing processes for the laser material processing of tomorrow in hall 4 at stand 4E75. With blown bomb shells the LZH will present first results of a research project on civil security.

At this year's LASYS, the LZH will exhibit light-based processes such as cutting, welding, ablation and structuring as well as additive manufacturing for...

Im Focus: Self-illuminating pixels for a new display generation

There are videos on the internet that can make one marvel at technology. For example, a smartphone is casually bent around the arm or a thin-film display is rolled in all directions and with almost every diameter. From the user's point of view, this looks fantastic. From a professional point of view, however, the question arises: Is that already possible?

At Display Week 2018, scientists from the Fraunhofer Institute for Applied Polymer Research IAP will be demonstrating today’s technological possibilities and...

Im Focus: Explanation for puzzling quantum oscillations has been found

So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics

Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

In focus: Climate adapted plants

25.05.2018 | Event News

Save the date: Forum European Neuroscience – 07-11 July 2018 in Berlin, Germany

02.05.2018 | Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

 
Latest News

In focus: Climate adapted plants

25.05.2018 | Event News

Flow probes from the 3D printer

25.05.2018 | Machine Engineering

Less is more? Gene switch for healthy aging found

25.05.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>