Navigation Links
Neural mapping paints a haphazard picture of odor receptors

CAMBRIDGE, Mass., Feb. 3, 2009 -- Despite the striking aromatic differences between coffee, peppermint, and pine, a new mapping of the nose's neural circuitry suggests a haphazard patchwork where the receptors for such disparate scents are as likely as not to be neighbors.

Inexplicably, this seemingly random arrangement is faithfully preserved across individuals and even species, with cells that process the same scent located in precisely the same location on the olfactory bulb, the brain's first processing station for odors.

The crazy-quilt map of odor-processing neurons on the front lines of the olfactory system is described by Harvard University neuroscientists in the February issue of the journal Nature Neuroscience.

"It had been thought that the layout of the olfactory bulb was variable from individual to individual, but followed a chemotopic order where cells handling similar odor responses are near each other," says Markus Meister, the Jeff C. Tarr Professor of Molecular and Cellular Biology in Harvard's Faculty of Arts and Sciences. "Here we show that the layout is actually very precise -- the same from animal to animal -- but doesn't appear to follow any chemotopic order whatsoever."

Working with mice and rats, Meister and colleague Venkatesh N. Murthy recorded neural responses to several hundred distinct odors, including anise, beer, cloves, coffee, ginger, lemon, orange, peppermint, pine, rose, and even fox pheromones. The neuroscientists found that across individuals and even across the two species, bundles of neurons from a given type of odor receptor -- known as glomeruli -- were found in almost exactly the same spot on the olfactory bulb, a sensory structure measuring some four to five millimeters across and located at the very front of the brain.

"Glomeruli from different receptors line the surface of the olfactory bulb like an array of close-packed marbles," says Murthy, professor of molecular and cellular biology at Harvard. "Across individuals the location of a given glomerulus varies by only one array position. Compared to the size of the map, this represents a remarkable developmental precision of one part in 1,000."

Meister and Murthy then analyzed whether nearby glomeruli detect similar odors, such as those with similar chemical structures. Neuroscientists have previously hypothesized axes of similarities along which odors might be classified.

"One might expect that nearby glomeruli should have similar odor sensitivities," Meister says, "but we were surprised to find this was not the case. The odor response spectra of two neighboring glomeruli were as dissimilar as those of distant glomeruli."

This seemingly haphazard layout of sensory properties stands in marked contrast to other brain maps, such as those governing vision, touch, and hearing. In these three cases, our brains represent the outside world using ordered maps -- such as when neighboring points in visual space activate neighboring points on the retina.

"That sort of arrangement makes sense, since most brain computation is local, relying on short connections between nearby cells," Murthy says. "This is necessary because the connections between neurons occupy most of the volume available to the brain, and long-distance connections require more of this volume."

Meister and Murthy suspect that the deliberate randomness in rodents' odor maps is likely also found in humans, which have only one-third as many receptors but are capable, in some extreme cases, of discerning tens of thousands of distinct smells.


Contact: Steve Bradt
Harvard University

Related biology news :

1. I feel your pain: Neural mechanisms of empathy
2. Obesity starts in the head? 6 newly discovered genes for obesity have a neural effect
3. Neural mechanisms of value bias in the human visual cortex
4. NeuralIQ Expands Global Leadership Team, Names Donnie Blanks CEO
5. Neural cell transplants may help those with Parkinsons disease
6. MIT aids creation of neural prosthetic devices
7. Neural stem cell study reveals mechanism that may play role in cancer
8. Studies offer guide as protein interaction mapping comes of age
9. New rainforest mapping technology gets huge support
10. Mapping a clan of mobile selfish genes
11. Chemical equator discovery will aid pollution mapping
Post Your Comments:
(Date:6/2/2016)... 2, 2016   The Weather Company , an IBM ... an industry-first capability in which consumers will be able to ... ask questions via voice or text and receive relevant information ... Marketers have long sought an advertising solution that ... be personal, relevant and valuable; and can scale across millions ...
(Date:5/24/2016)... care by providing unparalleled technology to leaders of the medical imaging industry.  As such, ... to the range of products distributed by Ampronix. Photo - ... ... ... With ...
(Date:5/12/2016)... May 12, 2016 , a ... the overview results from the Q1 wave of its ... wave was consumers, receptivity to a program where they ... a health insurance company. "We were surprised ... says Michael LaColla , CEO of Troubadour Research, ...
Breaking Biology News(10 mins):
(Date:6/27/2016)... , ... June 27, 2016 , ... ... for Amgen, will join the faculty of the University of North Carolina ... professor of strategy and entrepreneurship at UNC Kenan-Flagler, with a focus on the ...
(Date:6/27/2016)... BOSTON , June 27, 2016   Ginkgo ... biology to industrial engineering, was today awarded as ... a selection of the world,s most innovative companies. ... at scale for the real world in the ... organism engineers work directly with customers including Fortune ...
(Date:6/24/2016)... SAN DIEGO , June 24, 2016 /PRNewswire/ ... that more sensitively detects cancers susceptible to PARP ... individual circulating tumor cells (CTCs). The new test ... of HRD-targeted therapeutics in multiple cancer types. ... therapies targeting DNA damage response pathways, including PARP, ...
(Date:6/24/2016)... ... 24, 2016 , ... Researchers at the Universita Politecnica delle Marche in Ancona ... or pleural mesothelioma. Their findings are the subject of a new article on the ... are signposts in the blood, lung fluid or tissue of mesothelioma patients that can ...
Breaking Biology Technology: