Posts tagged smell
Articles and news from the latest research reports.
A new study of the sense of smell lends support to a controversial theory of olfaction: Our noses can distinguish both the shape and the vibrational characteristics of odorant molecules.
The study, in the journal Physical Chemistry Chemical Physics, demonstrates the feasibility of the theory – first proposed decades ago – that the vibration of an odorant molecule’s chemical bonds – the wagging, stretching and rocking of the links between atoms – contributes to our ability to distinguish one smelly thing from another.
“The theory goes that when the right odorant binds to its receptor, the odorant’s molecular vibration allows electrons to transfer from one part of the receptor to another,” said University of Illinois physics and Beckman Institute professor Klaus Schulten, who conducted the analysis with postdoctoral researcher Ilia Solov’yov and graduate student Po-Yao Chang. “This electron transfer appears to fine-tune the signal the receptor receives.”
(Watch a video about the research.)
Scientists have claimed to have solved the mystery of why coffee never tastes as good as it smells.
Apparently, the act of swallowing the drink sends a burst of aroma up the back of the nose from inside the mouth, activating a “second sense of smell” in the brain that is less receptive to the flavour, causing a completely different and less satisfying sensation.
“We have got two senses of smell. One sense is when you inhale things from the environment into you, and the other is when the air comes out of you up the nasal passage and is breathed out through the nose,” the Telegraph quoted Prof Barry Smith, of the University of London, as saying at the British Science Festival in Aberdeen.
The phenomenon is down to the fact that, although we have sensors on our tongue, 80 percent of what we think of as taste actually reaches us through smell receptors in our nose, the paper said. The receptors, which relay messages to our brain, react to odours differently depending on which direction they are moving in, it added.
In the case of coffee, the taste is also hampered by the fact that 300 of the 631 chemicals that combine to form its complex aroma are wiped out by saliva, causing the flavour to change before we swallow it, Prof Smith added.
Scientists have restored the sense of smell in mice through gene therapy for the first time — a hopeful sign for people who can’t smell anything from birth or lose it due to disease.
The achievement in curing congenital anosmia — the medical term for lifelong inability to detect odors — may also aid research on other conditions that also stem from problems with the cilia. Those tiny hair-shaped structures on the surfaces of cells throughout the body are involved in many diseases, from the kidneys to the eyes.
The new findings, published online in Nature Medicine, come from a team at the University of Michigan Medical School and their colleagues at several other institutions.
Smelling a skunk after a cold: Brain changes after a stuffed nose protect the sense of smell
A new Northwestern Medicine study shows that after the human nose is experimentally blocked for one week, brain activity rapidly changes in olfactory brain regions. This change suggests the brain is compensating for the interruption of this vital sense. The brain activity returns to a normal pattern shortly after free breathing has been restored.
Previous research in animals has suggested that the olfactory system is resistant to perceptual changes following odor deprivation. This new paper focuses on humans to show how that’s possible. The study is published in the journal Nature Neuroscience.
"You need ongoing sensory input in order for your brain to update smell information," said Keng Nei Wu, the lead author of the paper and a graduate student in neuroscience at Northwestern University Feinberg School of Medicine. "When your nostrils are blocked up, your brain tries to adjust to the lack of information so the system doesn’t break down. The brain compensates for the lack of information so when you get your sense of smell back, it will be in good working order."
Mice have system to handle smell of fear
July 23, 2012
Mice appear to have a specialized system for detecting and at least initially processing instinctually important smells such as those that denote predators. The finding raises a question about whether their response to those smells is hardwired.
A separate subsystem for the smell of fear. Experiments in mice suggest neurons that detect odors associated with an instinctive response — like fleeing when an approaching predator is detected — are configured differently than other olfactory neurons. Further research could determine whether this system automatically triggers flight or other primal behaviors.Credit: Mike Cohea/Brown University
PROVIDENCE, R.I. [Brown University] — A new study finds that mice have a distinct neural subsystem that links the nose to the brain and is associated with instinctually important smells such as those emitted by predators. That insight, published online this week in Proceedings of the National Academy of Sciences, prompts the question whether mice and other mammals have specially hardwired neural circuitry to trigger instinctive behavior in response to certain smells.
In the series of experiments and observations described in the paper, the authors found that nerve cells in the nose that express members of the gene family of trace amine-associated receptors (TAAR) have several key biological differences from the much more common and diverse neurons that express members of the olfactory receptor gene family. Those other nerve cells detect a much broader range of smells, said corresponding author Gilad Barnea, the Robert and Nancy Carney Assistant Professor of Neuroscience at Brown University.
The differences between TAAR neurons and olfactory receptor neurons led Barnea and his co-authors to conclude that they form an independent subsystem for certain smells.
“Our observations suggest that the TAAR-expressing sensory neurons constitute a distinct olfactory subsystem that extracts specific environmental cues that then elicit innate responses,” Barnea said.