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 A novel socio-ecological approach helps identifying suitable wolf habitats
17.02.2017 | Universität Zürich

nachricht New, ultra-flexible probes form reliable, scar-free integration with the brain
16.02.2017 | University of Texas at Austin

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Biocompatible 3-D tracking system has potential to improve robot-assisted surgery

17.02.2017 | Medical Engineering

Real-time MRI analysis powered by supercomputers

17.02.2017 | Medical Engineering

Antibiotic effective against drug-resistant bacteria in pediatric skin infections

17.02.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>