Whether different odors can be quickly distinguished depends on certain synapses in the brain that inhibit nerve stimulation. The researchers in Professor Dr. Thomas Kuner’s team at the Institute of Anatomy and Cell Biology at Heidelberg University Medical School and Dr. Andreas Schäfer at the Max Planck Institute for Medical Research have shown that mice in which a certain receptor in the olfactory center is missing can distinguish similar smells more quickly than mice without genetic manipulation. This behavior was directly attributed to inhibitor loops between adjacent nerve cells.
The discovery of the activation principle of “lateral inhibition” in the eye 43 years ago by Haldan K. Hartline, George Wald, and Ragnar Granit was honored with a Nobel Prize. The Heidelberg researchers have for the first time succeeded in confirming the same mechanism for the olfactory system, from the molecular level to behavior. The results of the studies were published in the prestigious journal “Neuron”.
Odors attach to receptors of olfactory cells in nasal mucosa, where they trigger nerve signals. These signals are processed in what is known as the olfactory bulb, a part of the brain. In the neuronal network, the incoming signal is converted to a specific electrical pattern that is transmitted to the cerebral cortex and other areas of the brain and is recognized there.
Local inhibitor loops make recognizing smells more precise
Professor Kuner and his team have now shown for the first time how neuronal processing of olfactory stimuli directly affects the behavior of test animals. “We manipulated information processing very specifically in the olfactory bulb and then measured the effect of this genetic manipulation based on reaction time. We were thus able to prove that the test animals, due to localized inhibitor loops, could distinguish very similar odor combinations much faster, yet very reliably,” explained Professor Kuner.
Inhibition via interneurons acts as a kind of filter by amplifying strong stimuli and further weakening weak stimuli. This makes the essential information easier to recognize. In the test animals, reaction time was reduced by about 50 ms. The time needed by test animals to learn various odors and their memory capability remained unaffected. Recognition of simple odors was also unchanged.
The researchers delivered a certain enzyme, cre recombinase, directly into the nerve cells of the olfactory bulb of young mice via a viral gene ferry. In the genome of these mice, a certain gene segment was removed using genetically introduced recognition sites of these enzymes. This led to the deletion of a receptor in the interneurons. This targeted manipulation made the inhibitor loops especially active. Using the usual “knock-out” models, in which the gene is deactivated in the entire body, the subsequent selective behavior could not have been observed. In a sophisticated experimental design, the mice then had to learn to recognize simple and complex odors composed of several aromatic substances. Using electrophysiological measurements, imaging processes, and anatomical techniques, a link was then created from the molecule to behavior.
NM Abraham, V Egger, DR Shimshek, R Renden, I Fukunaga, R Sprengel, PH Seeburg, M Klugmann, TW Margrie, AT Schaefer, T Kuner. Synaptic inhibition in the olfactory bulb accelerates odor discrimination in mice. Neuron, 2010, 65: 399–411
DOI 10.1016/j.neuron.2010.01.009For more information in the Internet:
Contact person:Professor Dr. Thomas Kuner
Dr. Thomas Kuner | EurekAlert!
Multi-institutional collaboration uncovers how molecular machines assemble
02.12.2016 | Salk Institute
Fertilized egg cells trigger and monitor loss of sperm’s epigenetic memory
02.12.2016 | IMBA - Institut für Molekulare Biotechnologie der Österreichischen Akademie der Wissenschaften GmbH
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...
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...
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,...
Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water
In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...
The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.
Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
02.12.2016 | Medical Engineering
02.12.2016 | Agricultural and Forestry Science
02.12.2016 | Physics and Astronomy