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uni'wissen 02-2012 ENG

Prof. Dr. Ulrich Egert studied biology in Tübingen and Durham, England. He wrote his dissertation on the development of thin- film electrode arrays and their use in neurophysiol- ogy at the Natural and Medical Sciences Institute of the University of Tübin- gen. In 2005 he completed his habilitation at the Fac- ulty of Biology of the Uni- versity of Freiburg. In 2008 he established the Labora- tory for Biomicrotechnology, which has 15 employees today. He also serves as coordinator of “Bernstein Focus: Neurotechnology Freiburg/Tübingen,” a pri- ority project funded by the Federal Ministry of Educa- tion and Research, as di- rector of the Bernstein Center Freiburg, and as co-director of the new Cluster of Excellence BrainLinks–BrainTools. He and his colleagues are working on reaching a bet- ter understanding of the foundations of activity dy- namics in neuronal net- works and clarifying their relation to diseases of the nervous system and their treatment. Further Reading Froriep, U. P./Kumar, A./Cosandier-Rimélé, D./Häussler, U./Kilias, A./Haas, C. A./Egert, U. (2012): Altered theta coupling between medial entorhinal cortex and dentate gyrus in temporal lobe epilepsy. In: Epilepsia, doi: 10.1111/j.1528 – 1167.2012.03662.x Frey, U./Egert, U./Heer, F./Hafizovic, S./ Hierlemann, A. (2009): Microelectronic system for high-resolution mapping of extracellular electric fields applied to brain slices. In: Bio- sensors and Bioelectronics 24/7, p. 2191– 2198. On the Internet platform Surprising Science, Prof. Dr. Carola Haas from the Freiburg University Medi- cal Center, who collaborates with Prof. Dr. Egert at the Cluster of Excellence BrainLinks–BrainTools, explains her fundamental medical research on epilepsy, to which mi- crosystems engineering is making important contributions. the-brain-and-technology/epilepsy-in-a-model/ all of their resources immediately.” This corre- sponds closely to the situation that can be found in clustered networks. The activity of the neu- rons in an artificial network of this kind can be designed in a simulation to be functionally simi- lar to a biological network. “It looks as if we were replacing one chaos with another,” says Egert, “but that is not the case.” On the contrary, the various paths of excitation in the electrode array can be precisely traced and even influenced. Epilepsy research provides the neuroscien- tists access to the biological networks in the brains of mammals. Epileptic areas of the brain undergo restructurings that change the neural networks permanently. Mesial temporal lobe epi- lepsy, which occurs in the hippocampus, often cannot be treated adequately with drugs. Sur- geons therefore often remove the tissue in order to prevent an excitation from occurring. The sci- entists initially failed in their attempt to simulate the excitation in a brain slice of a modified sec- tion of the hippocampus. “We didn’t succeed in causing epilepsy in the tissue section.” In further experiments with epileptic mice, however, they discovered that various sub-networks with incor- rectly functioning interactions in the hippocam- pus and in the so-called entorhinal cortex react with one another in a feedback loop. “We do not yet know precisely how this leads to epilepsy, but we find it systematically and only in epileptic animals,” says Egert. The scientists found similar processes in cell cultures: sponta- neous transitions between normal and extremely strong activity, like in the epileptic system. “We are now asking ourselves what these two pro- cesses have in common and whether we can re- pair them. We have found a new approach for intervening, but we are not yet certain whether it will be successful.” In collaboration with Prof. Dr. Oliver Paul and Dr. Patrick Ruther from the De- partment of Microsystems Engineering, the neu- roscientists have defined new microelectrodes for simultaneously collecting data on different areas of the entorhinal cortex and the hippocam- pus. “But at the same time we are working with our cell cultures, in which we can stimulate the individual nerve cells and modify the networks without too much effort. Here we have entirely different possibilities for accessing and manipu- lating the samples than we do in experiments on animals.” Detail of a cell culture that has been colored with antibodies against a neuron-specific protein. The image shows the cell bodies as thick “knots” and the neuronal networks connecting them. Several non- neuronal cells are barely visible in the background. 7