Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Study reveals that odor discrimination is linked to the timing at which neurons fire

09.11.2006
Timing is everything. For a mouse trying to discriminate between the scent of a tasty treat and the scent of the neighborhood cat, timing could mean life or death. In a striking discovery, Carnegie Mellon University scientists have linked the timing of inhibitory neuron activity to the generation of odor-specific patterns in the brain's olfactory bulb, the area of the brain responsible for distinguishing odors.

Their work, appearing in the Nov. 8 issue of the Journal of Neuroscience, describes for the first time a cellular mechanism linking a specific stimulus to the timing at which inhibitory neurons fire. This breakthrough lays a cellular foundation for the "temporal coding hypothesis," which proposes that odor identity is encoded by the timing of neuronal firing and not the rate at which neurons fire.

Past research has shown that specific odors trigger unique patterns of electrical activity in the brain. Generating these patterns requires reliably timed inhibition, but relatively little was known about the timing of the activity of inhibitory neurons -- until now.

"There is a clear link between which odor is being presented and the time at which inhibitory neurons fire. This timing controls which excitatory neurons are active and at which time. This modulation contributes to the generation of reliable temporal patterns of neuronal activity," said Nathan Urban, an assistant professor of biological sciences at the Mellon College of Science at Carnegie Mellon.

... more about:
»Neuron »granule »inhibitory »odor »specific

Populations of mitral cells, a type of excitatory neuron in the olfactory bulb, receive input from neurons in the nose that respond to a single odorant. After receiving this input, the mitral cells convey messages about odor identity to other parts of the brain. But they don't simply relay information. Their activity, and therefore which message they send, is modulated by the inhibitory activity of granule cells. In a first, Urban has shown that the timing of granule cell firing encodes odor information.

Urban's work is especially provocative given that the traditional view holds that the rate of neuronal firing is what really matters, not the time that it takes for a stimulated neuron to fire. Recognition of a stimulus like an odor relies on the orchestrated firing of neurons, both ones that excite other neurons to relay a message as well as ones that inhibit or alter how a message is relayed.

"Our results indicate that the latency period before a single granule cell fires is associated with a specific odor, thus linking the timing of inhibitory modulation of mitral cell activity to odor identity. In other words, the timing of granule cell firing conveys different messages. In this case, the messages relay which odor is present," explained Urban.

Urban monitored the subtle-yet-coordinated activity of populations of granule cells in living brain slices using calcium imaging, an optical imaging technique that has never been applied to studies of the olfactory system. Urban loaded the neurons with a fluorescent dye that emits a yellow glow. This glow decreases when the dye binds to calcium. Because the flow of calcium ions into and out of cells corresponds to their firing, Urban was able to actually watch which neurons were firing and when.

Urban stimulated mitral cells, which in turn stimulated granule cells. He found that granule cells respond by firing over a range of times, from a fraction of a millisecond to hundreds of milliseconds. But, according to Urban, the most striking observation was that specific granule cells reliably fired with the same latency when they receive input from certain populations of mitral cells. Input from one group of mitral cells (hence, one set of odor receptors) caused certain granule cells to fire with a 500-millisecond delay, for example. Input from another set of mitral cells (a different set of odor receptors) caused the same granule cells to fire with a 50-millisecond delay. Thus, he found that the timing of granule cell firing is directly related to the input the mitral cells receive -- the original odorant.

"This is the first time we have seen reliable timing of firing. It turns out that cells are better at clocking their firing than previously thought," Urban said.

"This finding is a springboard to addressing other important questions," Urban added. "For example, what are the molecular mechanisms by which granule cells time their firing? We are now exploring this question, as well as how we can observe this odor-specific timing in living animals."

Lauren Ward | EurekAlert!
Further information:
http://www.cmu.edu

Further reports about: Neuron granule inhibitory odor specific

More articles from Life Sciences:

nachricht Newly discovered bacteria-binding protein in the intestine
08.12.2016 | University of Gothenburg

nachricht The balancing act: An enzyme that links endocytosis to membrane recycling
07.12.2016 | National Centre for Biological Sciences

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

Scientists track chemical and structural evolution of catalytic nanoparticles in 3-D

08.12.2016 | Materials Sciences

Decoding cement's shape promises greener concrete

08.12.2016 | Materials Sciences

Will Earth still exist 5 billion years from now?

08.12.2016 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>