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(Anatomy) Smell: Humans Have Ability to Track Odors

 
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PostPosted: Mon Dec 12, 2005 8:02 am    Post subject: (Anatomy) Smell: Humans Have Ability to Track Odors Reply with quote






Study shows humans have ability to track odors, much like bloodhounds
By Robert Sanders, Media Relations
Universitry of California, Berkeley
29 August 2005

BERKELEY – Though humans may never match the tracking ability of dogs, we apparently have the ability to sniff out and locate odors, according to a new study by scientists from the University of California, Berkeley.

Student volunteers presented with odors to one nostril or the other could reliably discern where the odor was coming from, and functional magnetic resonance images of their brains showed that the brain is set up to pay attention to the difference between what the left and right nostrils sense, much the way it can localize sounds by contrasting input from the ears.

"It has been very controversial whether humans can do egocentric localization, that is, keep their head motionless and say where the spatial source of an odor is," said study coauthor Noam Sobel, associate professor of psychology at UC Berkeley and a member of the campus's Helen Wills Neuroscience Institute. "It seems that we have this ability and that, with practice, you could become really good at it."

In future experiments, UC Berkeley biophysics graduate student Jess Porter and Sobel plan to train volunteers to track odors in the field and test the limits of odor localization in humans.

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

Forty years ago, Nobel Prize laureate Georg von Békésy claimed that humans had the ability to localize odors, based on experiments in 1964 with human subjects. He suggested this was done the same way we locate sounds: by contrasting either the intensity of the odor or the time of arrival.

Since then, however, scientists have had difficulty replicating his experiments, according to Sobel. One explanation for this failure was that von Békésy used chemicals that stimulate not only the olfactory nerve in the nose, but also a nasal sensory nerve, the trigeminal nerve. Most odors stimulate both, and some, like onions and ammonia, are stinging enough to bring tears to the eyes. Perhaps, some suggested, von Békésy's subjects were localizing odors based on trigeminal nerve stimulation, not olfactory nerve stimulation.

To eliminate this confusion, Porter and Sobel used two odors with minimal trigeminal stimulation - essence of rose (phenyl ethyl alcohol) and cloves (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 an artificial septum that provided separate air flow to each nostril.

In addition, they conducted similar experiments on five volunteers who had no olfactory nerves and therefore couldn't smell at all, a condition known as anosmia.

Normal subjects, 16 in all, were able to tell which nostril was receiving a squirt of scent, but anosmic volunteers could only localize the trigeminal odorants, Sobel said. This shows that humans are able to localize odors through the olfactory nerves alone.

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

The experiments were conducted with the subjects' heads inside a functional MRI to allow the scientists to see which areas of the brain were most active during sniffing and attempts to identify and localize odors. They found that the left and right nostrils have separate areas of the primary olfactory cortex - the brain's smell center - devoted to them, indicating that the brain at least encodes information that could help it localize an odor. A successful detection of an odor is accompanied by more activity in the region of the olfactory cortex associated with the particular nostril.

"While a subject was doing this task, I could look at the brain and tell you how accurate he or she would be on every trial and on the task overall," Sobel said. "So the fact that we have this predictive value in the data really suggests that we have actually successfully captured the mechanism."

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

"It's actually a very nice and elegant convergence of this area, the superior temporal gyrus, that appears to transform non-spatial information into spatial information," he said. "Together, these results are the first description of the mammalian brain mechanisms for extracting spatial information from smell."

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

"We think 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 to localize an odor wouldn't be allowed to sniff. That's almost like studying auditory localization but having your ears plugged. We actually enabled natural behavior, we enabled subjects to sniff, and we think that's a major difference."

In addition to Porter and Sobel, other authors of the Neuron paper were UC Berkeley senior scientist Rehan M. Khan of the Department of Psychology and graduate students Tarini Anand and Brad Johnson of the Department of Bioengineering. The work was supported by grants from the National Institutes of Health.

*************************************************************

Questions to explore further this topic:

What is the nose?

http://kidshealth.org/kid/body/nose_noSW.html
http://www.cyh.com/HealthTopic.....mp;id=1686

Besides smelling what does the nose do?

http://kidshealth.org/kid/body/nose_SW_p2.html

What is the olfactory system?

http://faculty.washington.edu/chudler/nosek.html

What is smell (odor, scent, aroma)?

http://yucky.kids.discovery.co.....00150.html
http://faculty.washington.edu/chudler/chsmell.html
http://www.tsbvi.edu/Outreach/...../smell.htm
http://www.cf.ac.uk/biosi/staf.....fact1.html
http://www.hhmi.org/senses/d110.html

Are taste and smell related?

http://www.ktca.org/newtons/11/tstesmll.html

Can people have problems with smell?


http://nihseniorhealth.gov/pro.....ll/01.html

Here is an animation on how the nose works:

http://www.innerbody.com/anim/nasal.html

Can other animals smell too?

http://www.nhm.org/exhibitions.....smell.html
http://news.nationalgeographic.....utans.html
http://www.ntnu.no/gemini/1998-01E/30.html
http://www.sandiegozoo.org/tea.....knows.html

What are pheromones?

http://www.nysaes.cornell.edu/pheronet/pherom.html
http://www.hhmi.org/senses/d230.html
http://www.colorado.edu/iec/FA.....mones.html

GAMES

http://www.sandiegozoo.org/kids/games/index.html
http://www.littledittle.com/kids_games/games.htm
http://library.thinkquest.org/.....leeric.htm


Last edited by adedios on Sat Jan 27, 2007 4:31 pm; edited 3 times in total
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PostPosted: Mon May 22, 2006 8:28 am    Post subject: How We Smell Reply with quote

How We Smell

By Corey Binns
Special to LiveScience
posted: 22 May 2006
08:37 am ET
http://www.livescience.com/hum.....smell.html

Your nose is one powerful protrusion. Whether it's a big honker or a little button, if it is working correctly you can sense a skunk from only 0.000,000,000,000,071 of an ounce of offensive spray.

Animals can trace even tinier trails. Male luna moths, for example, track females from 5 miles away.

Such nosiness is important for the survival of almost all creatures: to find food, avoid being eaten, and pick proper mates. It warns us about rotten milk, a burning house, or an unhappy skunk, and can turn our attention to attractive potential dates.

Nosing around

Despite its value, scientists knew little about how we sensed scents before the 2004 Nobel Prize winners took a jab at it.

In 1991, laureates Richard Axel of Howard Hughes Medical Institute and Linda Buck at the Fred Hutchinson Cancer Research Center discovered about 1,000 genes that encode for olfactory receptors inside the human nose. They also found that each receptor is tuned for only a small number of odors.

Researchers recently determined which receptors in a fruit fly detect which specific odors. They plotted each receptor to form an entire map of where the fly senses each scent.

"The results of our analysis allow us to make predictions about which odors smell alike to an animal, and which smell different," said Yale University molecular biologist John Carlson who worked with then-grad student Elissa Hallem, now a molecular biologist at the California Institute of Technology.

Their findings are published in the April issue of the journal Cell.

Take a deep breath

Although we don't yet have a scent map for humans, thanks to Axel and Buck, scientists know how you smell.

Take a deep breath. Air is sucked up into your nostrils over bony ridges called turbinates, which add more surface area to your sniffer. The air travels over millions of olfactory receptor neurons that sit on a stamp-size sheet, the olfactory epithelium, on the roof of the nasal cavity. Odor molecules in the air stimulate and inhibit the receptors.

Each aroma sets off a signal made by the receptors that travels along the olfactory nerve to the olfactory bulb. The olfactory bulb sits underneath the front of your brain. Signals from the bulb tell your brain what reeks.

Humans can recognize 10,000 different odors. However, no two people sense anything the same..

Good weather for smelling

Several factors, including genes, skin type, and diet are related to how smells smell. Even the weather can alter an odor.

When we're hungry, our smell sense grows stronger
Women have keener whiffers than men and like the smell of a symmetrical man best.
At certain times of the month, men say the scent of a woman is more attractive.
Our schnozzes are at their worst in the mornings, improving as the day goes on.
Some people endure long-term proboscis problems.

Smell disorders most often stem from injuries to the head and upper respiratory infections. Other causes include hormonal disturbances, dental problems, and exposure to chemicals such as insecticides and solvents can also cause smell disorders. Radiation for treating head or neck cancer can create smelling problems as well.

A nose that's in less than tip-top condition can affect taste buds too. Researchers say 80 percent of the flavors we taste come from what we smell, which is why foods become relatively flavorless when we're plugged up.
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PostPosted: Wed Nov 22, 2006 11:12 am    Post subject: The smell of money Reply with quote

National Science Foundation
21 November 2006

The smell of money

Research suggests an absence of metallic chemicals in the strong metallic odors that result from people handling coins and other metals
It's not hard to recall the pungent scent of a handful of pocket change. Similar smells emanate from a sweat-covered dumbbell or the water emerging from an old metal pipe. Yet no one has been able to identify the exact chemical cause of these familiar odors.

Now, researchers supported by a National Science Foundation (NSF) MUSES award and the UFZ Environmental Research Center in Germany have shown that these odor molecules come not from the penny or the pipes, but from metal-free chemicals erupting into the air when organic substances like sweat interact with the metallic objects.

The researchers--Andrea Dietrich, Dietmar Glindemann, Hans-Joachim Staerk and Peter Kuschk, all from Virginia Tech in Blacksburg--published their findings in the Oct. 20, 2006, Angewandte Chemie International Edition.

"We are the first to demonstrate that when humans describe the 'metallic' odor of iron metal, there are no iron atoms in the odors," said Dietrich. "The odors humans perceive as metallic are really a body odor produced by metals reacting with skin."

Because the makeup of byproduct molecules depends on which organic substances are reacting, the researchers believe the findings could help identify problem odors in potable water or aid doctors searching for disease markers in sweat or other body fluids.

The study, which focused mainly on the reactions of biological fluids with iron, also examined the scents emanating from iron in blood.

"We speculate that the 'blood scent' may result from skin reacting with ferrous iron because the same 'metallic' odor is produced if you rub blood on skin," said Dietrich.

One of the chemicals produced in the reaction is 1-octen-3-one, which has a mushroom-metallic smell and very low odor threshold, meaning that humans can smell it in extremely minute concentrations.

"This may have provided an evolutionary advantage that allowed early humans to track wounded comrades or prey," Dietrich added.


###
NSF-PR 06-164

The National Science Foundation (NSF) is an independent federal agency that supports fundamental research and education across all fields of science and engineering, with an annual budget of $5.58 billion. NSF funds reach all 50 states through grants to nearly 1,700 universities and institutions. Each year, NSF receives about 40,000 competitive requests for funding, and makes nearly 10,000 new funding awards. The NSF also awards over $400 million in professional and service contracts yearly.

Receive official NSF news electronically through the e-mail delivery and notification system, MyNSF (formerly the Custom News Service). To subscribe, visit http://www.nsf.gov/mynsf/ and fill in the information under "new users".

Useful NSF Web Sites:
NSF Home Page: http://www.nsf.gov
NSF News: http://www.nsf.gov/news/
For the News Media: http://www.nsf.gov/news/newsroom.jsp
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Awards Searches: http://www.nsf.gov/awardsearch/
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PostPosted: Tue Dec 19, 2006 8:02 am    Post subject: Two nostrils are better than one Reply with quote

University of California - Berkeley
18 December 2006

Sniffers show that humans can track scents, and that two nostrils are better than one

Berkeley -- University of California, Berkeley, graduate student Allen Liu last Friday donned coveralls, a blindfold, earplugs and gloves, then got down on all fours and sniffed out a 33-foot chocolate trail through the grass.

This was no fraternity initiation, but part of an experiment to find out whether mammals compare information coming from their two nostrils in order to aid scent-tracking performance, much like they compare information from their ears in order to locate a sound.

In a paper appearing this week in the advance online edition of Nature Neuroscience, UC Berkeley researchers report conclusive evidence from these experiments that humans do indeed gain a performance advantage from cross-nostril comparisons. They also found that humans can scent-track, and that, with training, they can improve their accuracy significantly while nearly doubling their speed along the scent trail.

In one experiment, the authors found that while volunteers with one nostril blocked could still track a scent - in this experiment, essence of chocolate - volunteers with two open nostrils tracked a scent quicker and with fewer deviations from the trail. "We were asking the question, 'Are two nostrils better than one"'" said lead author Jess Porter, a graduate student in biophysics at UC Berkeley. "The answer is yes."

Apparently, according to Porter and her colleagues, the mammalian brain compares smells between nostrils to tell where an odor is coming from in the same way that the brain compares the sounds entering a person's two ears to locate a source. Until now, many researchers thought this was unlikely because a mammal's nostrils, in a mouse, for example, are too close together to receive distinctly different smells.

"The human brain compares information from two 'noses' to turn smell information into spatial information," said Noam Sobel, associate professor of neuroscience and psychology and member of the program in biophysics at UC Berkeley.

Sobel hopes to use information from these experiments to design scent-tracking robots equipped with his eNose, an electronic nose that one day could detect odors such as that from an explosive mine.

To test Sobel and Porter's smell hypothesis, the UC Berkeley researchers soaked a 33-foot (10-meter) string in chocolate essence and laid it in the grass outside Barker Hall, located at the northwest corner of the UC Berkeley campus. They then garbed volunteers to block their senses of sight, hearing and touch, eliminating all clues other than smell to guide them along the trail. Sniffing like bloodhounds, two-thirds of 32 subjects were able to follow the chocolate scent to the end of the trail within three attempts. All volunteers zigzagged along the trail in the same way that tracking dogs follow a scent.

The researchers then trained four of these volunteers to see if they could improve. All were able to double their speed along the track within just a few days and deviated much less from the scent trail than on their first attempts. The researchers measured subjects' sniffs and noticed that the faster the subjects moved along the trail, the more rapid their sniffing - just as with dogs, though not as fast as the six sniffs per second rate exhibited by dogs.

The big question, however, was whether two nostrils allow scent localization in the same way that a human's two ears and eyes help locate sounds and sights.

To further test this, the researchers devised an ingenious nasal "prism" that mixed scents from the outside world and then presented this to both nostrils, so that there was no difference between what the nostrils smelled. The four subjects were half as accurate at tracking smells under these conditions.

Independent measurements showed that a human's two nostrils sample odors from distinct areas separated by approximately 1.5 inches (3.5 centimeters), more than enough distance to distinguish the edge of a scent plume.

All of these experiments put the lie to a common assumption that humans are lousy smellers compared to all other mammals. While it's true that humans are predominantly visual creatures, Sobel said, their olfactory sense can be compared to that of dogs and other mammals.

"Our sense of smell is less keen partly because we put less demand on it," Porter said. "But if people practice sniffing smells, they can get really good at it."

###
The work, which will be published in the journal's January 2007 issue, was supported by the Army Research Office and the National Institute on Deafness and other Communication Disorders of the National Institutes of Health.
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PostPosted: Sat Jan 27, 2007 9:03 am    Post subject: Odor-Chasing Penguins Reply with quote

Odor-Chasing Penguins
M. Price

Jan. 31, 2007

The smell of rotten eggs probably makes you cringe. But, for penguins, this smell might mean there's a meal nearby.
New research shows that penguins are attracted to this rotten-egg smell and probably use it when foraging for food in the ocean. The study is one of the first to show that penguins have a functioning sense of smell.

For the full article:

http://www.sciencenewsforkids....../Note2.asp
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PostPosted: Wed Feb 14, 2007 7:52 am    Post subject: Instruction Manual for Creating a Molecular Nose Reply with quote

February 9th, 2007
Max Planck Society

Instruction Manual for Creating a Molecular Nose


Max Planck researchers incorporate odorant receptors into artificial membranes

An artificial nose could be a real benefit at times: this kind of biosensor could sniff out poisons, explosives or drugs, for instance. Researchers at the Max Planck Institute for Polymer Research and the Max Planck Institute of Biochemistry recently revealed a technique for integrating membrane proteins into artificial structures. Membrane proteins have several important functions in the cell, one of which is to act as receptors, passing on signals from molecules in the air, for example, to the cell interior. They are thus ideal biosensors, but until now were difficult to access in the lab. However, Max Planck scientists have now managed to incorporate in-vitro synthesized membrane proteins directly into artificial lipid membranes (Angewandte Chemie, International Edition, January 15, 2007).

For the full article:

http://www.mpg.de/english/illu.....200702091/
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PostPosted: Fri Mar 16, 2007 8:14 am    Post subject: The Secret to Sniffing: How We Smell So Well Reply with quote

The Secret to Sniffing: How We Smell So Well

By Charles Q. Choi
Special to LiveScience
posted: 15 March 2007
12:02 pm ET

Sniffing the air does more than just vacuum odors into your nose. It also ramps up electrical signals from the snout to the brain, helping the schnoz detect even faint scents.

"Sniffing helps us to smell better," Minghong Ma, a University of Pennsylvania neuroscientist, told LiveScience.

Ma and her colleagues learned the secret to sniffing by investigating mice noses. The scientists puffed a mix of odors past the rodent sniffers, such as those in almond-like and banana-like fragrances. As expected, this generated a response in the olfactory neurons, the primary nose cells behind perception of scents.

For the full article:

http://www.livescience.com/hum.....smell.html
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PostPosted: Mon Apr 30, 2007 8:18 am    Post subject: Artificial Snot Enhances Electronic Nose Reply with quote

Artificial Snot Enhances Electronic Nose

University of Warwick
30 April 2007

Researchers at The University of Warwick and Leicester University have used an artificial snot (nasal mucus) to significantly enhance the performance of electronic noses.

The researchers have coated the sensors used by odour sensing "electronic noses” with a mix of polymers that mimics the action of the mucus in the natural nose. This greatly improves the performance of the electronic devices allowing them to pick out a more diverse range of smells.

A natural nose uses over 100 million specialised receptors or sensors which act together in complex ways to identify and tell apart the molecules they encounter. Electronic noses, used in a number of commercial settings including quality control in the food industry, use the same method but often have less than 50 sensors. This means that electronic noses can discern a much smaller range of smells than the natural nose.

However the University of Warwick and Leicester University team have found a way to replicate in their electronic devices how the natural nose’s mucus enhances our sense of smell.

In the natural nose the thin layer of mucus dissolves scents and separates out different odour molecules in a way they arrive at the noses receptors at different speeds/times. Humans are then able to use this information on the differences in time taken to reach different nose receptors to pick apart a diverse range of smells.

The Warwick and Leicester team have employed an artificial mucus layer to mimic this process. They placed a 10-micron-thick layer of a polymer normally used to separate gases on the sensors within their electronic nose. They then tested it on a range of compounds and found that their artificial snot substantially improved the performance of their electronic nose allowing it to tell apart smells such as milk and banana which had previously been challenging smells for the device.

University of Warwick researcher Professor Julian Gardner says: “Our artificial mucus not only offers improved odour discrimination for electronic noses it also offers much shorter analysis times than conventional techniques”.

The final device including the sensors and the artificial mucus is contained in a relatively thin piece of plastic just a few centimeters square and costing less than five UK pounds (10 US Dollars) to produce.

The research has just been published in the journal Proceedings of the Royal Society and the research was funded by EPSRC
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PostPosted: Sat Jul 07, 2007 7:25 am    Post subject: Restoring Scents Reply with quote

Week of July 7, 2007; Vol. 172, No. 1 , p. 10

Restoring Scents
Faulty sniffers may get help
Janet Raloff

Betty (not her real name) remembers the day 9 years ago when she fully experienced an orange. As she split the fruit's skin, the sections, citrus scents sprayed into the air and the 51-year-old woman experienced a sensory epiphany: "Whoa! This is an orange. My God, this is what an orange smells like."

For the full article:

http://sciencenews.org/articles/20070707/bob9.asp
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PostPosted: Sat Nov 10, 2007 7:14 am    Post subject: MIT's 'electronic nose' could detect hazards Reply with quote

MIT's 'electronic nose' could detect hazards
Anne Trafton, News Office
October 30, 2007


A tiny "electronic nose" that MIT researchers have engineered with a novel inkjet printing method could be used to detect hazards including carbon monoxide, harmful industrial solvents and explosives.

Led by MIT professor Harry Tuller, the researchers have devised a way to print thin sensor films onto a microchip, a process that could eventually allow for mass production of highly sensitive gas detectors.

"Mass production would be an enormous breakthrough for this kind of gas sensing technology," said Tuller, a professor in the Department of Materials Science and Engineering (MSE), who is presenting the research Oct. 30 at the Composites at Lake Louise Conference in Alberta, Canada.

The prototype sensor, created by Tuller, postdoctoral fellow Kathy Sahner and graduate student Woo Chul Jung, members of MIT's Electroceramics Group in MSE, consists of thin layers of hollow spheres made of the ceramic material barium carbonate, which can detect a range of gases. Using a specialized inkjet print head, tiny droplets of barium carbonate or other gas-sensitive materials can be rapidly deposited onto a surface, in any pattern the researchers design.

The miniature, low-cost detector could be used in a variety of settings, from an industrial workplace to an air-conditioning system to a car's exhaust system, according to Tuller. "There are many reasons why it's important to monitor our chemical environment," he said.

For a sensor to be useful, it must be able to distinguish between gases. For example, a sensor at an airport would need to know the difference between a toxic chemical and perfume, Tuller said. To achieve this, sensors should have an array of films that each respond differently to different gases. This is similar to the way the human sense of smell works, Tuller explained.

"The way we distinguish between coffee's and fish's odor is not that we have one sensor designed to detect coffee and one designed to detect fish, but our nose contains arrays of sensors sensitive to various chemicals. Over time, we train ourselves to know that a certain distribution of vapors corresponds to coffee," he said.

In previous work designed to detect nitrogen oxide (NOx) emissions from diesel exhaust, the researchers created sensors consisting of flat, thin layers of barium carbonate deposited on quartz chips. However, the films were not sensitive enough, and the team decided they needed more porous films with a larger surface area.

To create more texture, they applied the barium carbonate to a layer of microspheres, hollow balls less than a micrometer in diameter made of a plastic polymer. When the microspheres are burned away, a textured, highly porous layer of gas-sensitive film is left behind.

The resulting film, tens of nanometers (billionths of a meter) thick, is much more sensitive than flat films because it allows the gas to readily permeate through the film and interact with a much larger active surface area.

At first, the researchers used a pipette to deposit the barium carbonate and microspheres. However, this process proved time-consuming and difficult to control.

To improve production efficiency, the researchers took advantage of a programmable Hewlett-Packard inkjet print head located in the MIT Laboratory of Organic Optics and Electronics. The inkjet print head, like that in a regular inkjet printer, can deposit materials very quickly and controllably. The special gas-sensitive "inks" used in this work were optimized for printing by Amy Leung, an MIT sophomore in chemical engineering.

This allows the researchers to rapidly produce many small, identical chips containing geometrically well-defined gas-sensing films with micrometer dimensions. Patterns of different gas-sensitive inks, just as in a color printer, can be easily generated to form arrays with very little ink required per sensor.

In future studies, the team hopes to create large arrays of gas-sensitive films with controlled three-dimensional shapes and morphologies.

The research is funded by the National Science Foundation.
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PostPosted: Fri Dec 07, 2007 3:09 pm    Post subject: Subliminal smells bias perception about a person's likeabili Reply with quote

Northwestern University
6 December 2007

Subliminal smells bias perception about a person's likeability

EVANSTON, Ill. --- Anyone who has bonded with a puppy madly sniffing with affection gets an idea of how scents, most not apparent to humans, are critical to a dog’s appreciation of her two-legged friends. Now new research from Northwestern University suggests that humans also pick up infinitesimal scents that affect whether or not we like somebody.

“We evaluate people every day and make judgments about who we like or don’t like,” said Wen Li, a post-doctoral fellow in the Cognitive Neurology and Alzheimer’s Disease Center at Northwestern’s Feinberg School of Medicine and lead author of the study. “We may think our judgments are based only on various conscious bits of information, but our senses also may provide subliminal perceptual information that affects our behavior.”

“Subliminal Smells Can Guide Social Preferences” was published in the December issue of Psychological Science. Besides Li, the study’s co-investigators include Isabel Moallem, Loyola University; Ken Paller, professor of psychology in the Weinberg College of Arts and Sciences at Northwestern; and Jay Gottfried, assistant professor of neurology at Feinberg and senior author of the paper.

Minute amounts of odors elicited salient psychological and physiological changes that suggest that humans get much more information from barely perceptible scents than previously realized.

To test whether subliminal odors alter social preferences, participants were asked to sniff bottles with three different scents: lemon (good), sweat (bad) and ethereal (neutral). The scents ranged from levels that could be consciously smelled to those that were barely perceptible. Study participants were informed that an odor would be present in 75 percent of the trials.

Most participants were not aware of the barely perceptible odors. After sniffing from each of the bottles, they were shown a face with a neutral expression and asked to evaluate it using one of six different rankings, ranging from extremely likeable to extremely unlikeable.

People who were slightly better than average at figuring out whether the minimal smell was present didn’t seem to be biased by the subliminal scents.

“The study suggests that people conscious of the barely noticeable scents were able to discount that sensory information and just evaluate the faces,” Li said. “It only was when smell sneaked in without being noticed that judgments about likeability were biased.”

The conclusions fit with recent studies using visual stimuli that suggest that top-down control mechanisms in the brain can be exerted on unconscious processing even though individuals have no awareness of what is being controlled.

“When sensory input is insufficient to provoke a conscious olfactory experience, subliminal processing prevails and biases perception,” Paller said. “But as the awareness of a scent increases, greater executive control in the brain is engaged to counteract unconscious olfaction.”

The acute sensitivity of human olfaction tends to be underappreciated. “In general, people tend to be dismissive of human olfaction and discount the role that smell plays in our everyday life,” said Gottfried. “Our study offers direct evidence that human social behavior is under the influence of miniscule amounts of odor, at concentrations too low to be consciously perceived, indicating that the human sense of smell is much keener than commonly thought.”

The study adds to a growing body of research suggesting that subliminal sensory information -- whether from scents, vision or hearing -- affects perception. “We are beginning to understand more about how perception and memory function,” Paller said, “by taking into account various types of influences that operate without our explicit knowledge.”
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PostPosted: Mon Dec 10, 2007 1:47 pm    Post subject: Homosexuality Turned On and Off in Fruit Flies Reply with quote

Homosexuality Turned On and Off in Fruit Flies
By Robert Roy Britt, LiveScience Managing Editor

posted: 09 December 2007 01:05 pm ET

While several studies find homosexuality in humans and other animals is biological rather than learned, a question remains over whether it's a hard-wired phenomenon or one that can be altered.


A new study finds drugs or genetic manipulation can turn the homosexual behavior of fruit flies on and off within a matter of hours. While the genetic finding supports the thinking that homosexuality is hard-wired, the drug finding surprisingly suggests it's not that simple.

In fact, homosexuality in the fruit flies seems to be regulated by how they interpret the scent of another.

For the full article:

http://www.livescience.com/ani.....genes.html
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PostPosted: Tue Dec 11, 2007 2:34 pm    Post subject: Aromatherapy: Something Smells Funny Reply with quote

Aromatherapy: Something Smells Funny
By Christopher Wanjek, LiveScience's Bad Medicine Columnist

posted: 11 December 2007 11:52 am ET

Odors have the power to alter moods, as I learned once sitting next to a shoeless fellow on a 22-hour delayed flight from China. But can smells heal the body, as is purported in the pseudoscience of aromatherapy?

For the full article:

http://www.livescience.com/hea.....smell.html
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