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Important adjustment process between the sense of balance and the eyes deciphered

Our eyes must be tightly coupled with our sense of balance to provide sharp and jitter-free images. If the adjustment is disturbed, our view is blurred and we get dizzy. Scientists at the Bernstein Center Munich, the LMU München and the Integrated Research and Treatment Center IFB-LMU have now deciphered an important step of this interaction; whether certain neurons transmit information about the start or the duration of the movement depends entirely on a single type of membrane channel and the cells' interconnections. Optimized therapies against vertigo and the development of jitter-free camera systems could benefit from this research.

Just three steps in the brain are necessary for processing data from the vestibular system and transferring them to the eye muscles. This allows the visual system to adjust to head movements within a fraction of a second. While in the first and last step, information is mainly transferred from the sensors and to the muscles, respectively, the second step is where the essential processing takes place. Scientists found that neurons with different properties are involved in this step: one type is only active during the initiation of a movement, while the other type sends signals during the entire movement. Recently, Dr. Stefan Glasauer, researcher at the Bernstein Center Munich and at the Ludwig-Maximilians-Universität München, and his PhD student Christian Rössert, in collaboration with Prof. Hans Straka, Neurobiologist at the LMU, have found out why this is so. In their study, presented in the Journal of Neuroscience*, they used the already well-understood balance organ of grass frogs.

Based on experimental data, the scientists created computer simulations that reproduced the information processing of these nerve cells. "In the simulation, we can supply the cells with any combination of ion channels, connect them in any way, and measure their behavior," explains Glasauer about the advantages of the models. And even more: "We can even make the simulated frog jump, in order to test its data processing," says Glasauer. First, the researchers examined in a simulated single cell the influence of certain membrane channels on the transmission of incoming stimuli. They found that cells with two different membrane channels have different functions: channels with the first type were suitable for the processing of the exact movement initiation time, while the other type discharged for the entire stimulus duration. In simulations with a number of nerve cells, Glasauer and Rössert found that the interconnection of the cells also plays an important role in processing. "The combination of experimental biology and modeling significantly helped in understanding essential basics of sensorimotor information processing," says Glasauer. The results are also relevant for clinical and technical research.

Besides others, patients with cerebellar damage could benefit from these research results. The affected individuals have problems in compensating rapid head movements by appropriate eye movements, but no problems in compensating for smooth movements. This might be due to a deficit in one of the two cell types. The highly efficient neuronal processing could also serve as a model for jitter-free camera systems that are used, for example, in driver assistance systems of cars or helicopters.

*Original publication: Rössert C, Moore L, Straka H, Glasauer S (2011), Cellular and network contributions to vestibular signal processing: impact of ion conductances, synaptic inhibition, and noise, J Neurosci, Volume 31, issue 23, 8359-8372

For further information please contact:

Dr. Stefan Glasauer Bernstein Center Munich and Ludwig-Maximilians-Universität München Department of Neurology Marchioninistr. 15, 81377 Munich, Germany Phone: +49-89-7095-4839 E-mail: sglasauer@nefo.med.uni-muenchen.de

idw :: 24.06.2011

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