Depending on the input signal, neurons generate action potentials either near or far away from the cell body, as researcher from Munich predict. This flexibility would improve our ability to localize sound sources.
In order to process acoustic information with high temporal fidelity, nerve cells may flexibly adapt their mode of operation according to the situation. At low input frequencies, they generate most outgoing action potentials close to the cell body.
Following inhibitory or high frequency excitatory signals, the cells produce many action potentials more distantly. This way, they are highly sensitive to the different types of input signals.
These findings have been obtained by a research team headed by Professor Christian Leibold, Professor Benedikt Grothe, and Dr. Felix Felmy from the Bernstein Center and the Bernstein Focus Neurotechnology in Munich and the LMU Munich, who used computer models in their study. The researchers report their results in the latest issue of The Journal of Neuroscience.
Did the bang come from ahead or from the right? In order to localize sound sources, nerve cells in the brain stem evaluate the different arrival times of acoustic signals at the two ears. Being able to detect temporal discrepancies of up to 10 millionths of a second, the neurons have to become excited very quickly. In this process, they change the electrical voltage that prevails on their cell membrane.
If a certain threshold is exceeded, the neurons generate a strong electrical signal—a so-called action potential—which can be transmitted efficiently over long axon distances without weakening. In order to reach the threshold, the input signals are summed up. This is achieved easier, the slower the nerve cells alter their electrical membrane potential.
These requirements—rapid voltage changes for a high temporal resolution of the input signals, and slow voltage changes for an optimal signal integration that is necessary for the generation of an action potential—represent a paradoxical challenge for the nerve cell. “This problem is solved by nature by spatially separating the two processes. While input signals are processed in the cell body and the dendrites, action potentials are generated in the axon, a cell process,” says Leibold, leader of the study. But how sustainable is the spatial separation?
In their study, the researchers measured the axons’ geometry and the threshold of the corresponding cells and then constructed a computer model that allowed them to investigate the effectiveness of this spatial separation. The researchers’ model predicts that depending on the situation, neurons produce action potentials with more or less proximity to the cell body.
For high frequency or inhibitory input signals, the cells will shift the location from the axon’s starting point to more distant regions. In this way, the nerve cells ensure that the various kinds of input signals are optimally processed—and thus allow us to perceive both small and large acoustic arrival time differences well, and thereby localize sounds in space.
The Bernstein Center Munich is part of the National Bernstein Network Computational Neuroscience in Germany. With this funding initiative, the German Federal Ministry of Education and Research (BMBF) has supported the new discipline of Computational Neuroscience since 2004 with over 170 million Euros. The network is named after the German physiologist Julius Bernstein (1835-1917).
Prof. Dr. Christian Leibold
Department Biology II
Großhaderner Straße 2
82152 Planegg-Martinsried (Germany)
Tel: +49 (0)89 2180-74802
S. Lehnert, M. C. Ford, O. Alexandrova, F. Hellmundth, F. Felmy, B. Grothe & C. Leibold (2014): Action potential generation in an anatomically constrained model of medial superior olive axons. Journal of Neuroscience, 34(15): 5370—5384.
http://neuro.bio.lmu.de/research_groups/res-leibold_ch personal website Christian Leibold
http://www.bccn-munich.de Bernstein Center München
http://www.uni-muenchen.de LMU Munich
http://www.nncn.de National Bernstein Network Computational Neuroscience
Mareike Kardinal | idw - Informationsdienst Wissenschaft
Symbiotic bacteria: from hitchhiker to beetle bodyguard
28.04.2017 | Johannes Gutenberg-Universität Mainz
Nose2Brain – Better Therapy for Multiple Sclerosis
28.04.2017 | Fraunhofer-Institut für Grenzflächen- und Bioverfahrenstechnik IGB
More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.
Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...
Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.
"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
28.04.2017 | Event News
20.04.2017 | Event News
18.04.2017 | Event News
28.04.2017 | Medical Engineering
28.04.2017 | Earth Sciences
28.04.2017 | Life Sciences