Every second, the brain's nerve cells exchange many billions of synaptic impulses. Two kinds of synapses ensure that this flow of data is regulated: Excitatory synapses relay information from one cell to the next, while inhibitory synapses restrict the flow of information.
Scientists at the Max Planck Institute of Neurobiology in Martinsried could now show, in cooperation with colleagues from the Ruhr University of Bochum, that excitatory and inhibitory synapses remain balanced – even if the brain undergoes reorganization. Following a small retinal lesion, the nerve cells in the mouse brain responsible for this particular region no longer received (excitatory) information. As a result, the cells reduced the number of their inhibitory synapses by 30% in the space of just one day. This down-regulated balance between excitation and inhibition could indicate to the nerve cells that it is time for them to reconfigure to partially compensate for the loss of information.
Nerve cells are "information addicts". To process and store new information or to optimize already existing ways of processing it, minute appendages emerge continually from their surface and grow towards neighboring cells. At the end of these appendages, a synapse can develop via which the two nerve cells can then exchange information. Scientists at the Max Planck Institute of Neurobiology in Martinsried and the Ruhr University of Bochum were already able to show how quickly such nerve cells can reorganize themselves even in the adult brain, so that they are constantly able to process information: After a small retinal lesion, the nerve cells responsible for processing information from this area were "out of work". However, during the weeks to follow, the neurobiologists observed that these nerve cells increased the number of appendages sent towards their neighbouring cells. The cells that had been temporarily redundant were thus reconnecting themselves and could take on new tasks within the processing network.
However, optimal processing in the brain depends not only on the circulation of information but also on the direct inhibition of the flow of information at given points. What actually happens to these so-called inhibitory synapses when conditions change in the brain? Since this area has hardly received any detailed scientific attention, the team of scientists set out to examine the fate of these synapses in the nerve cells that receive no information on account of the small retinal lesion.
"One possible outcome was that inhibitory synapses remained, maybe to inhibit these cells which would otherwise pass on no, or only meaningless, information", explains Tara Keck, whose study has just been published in the scientific journal Neuron. However, the neurobiologists discovered that precisely the opposite was the case. They showed that those cells which had been rendered redundant reduced the number of their inhibitory synapses by about one third within one day. Such was the extent of this downsizing that the imbalance in the flow of information, brought about by the loss of the excitatory signals from the retina, was quashed. "The exciting thing about this result is the insight that the brain appears to be constantly seeking to maintain the balance between excitation and inhibition", Keck relates.
The scientists already have a theory as to the importance of this lower level of the established balance. "The decimation of the inhibitory synapses may act as a signal to neighbouring cells by advertising: Nerve cells seeking work. Please get in touch", reflects Mark Hübener, the head of the study. The scientists now hope to establish whether this is indeed the case and whether more inhibitory synapses are produced to regain the original balance once the rewiring with other cells is complete.
Tara Keck, Volker Scheuss, R. Irene Jacobsen, Corette J. Wierenga, Ulf T. Eysel, Tobias Bonhoeffer, Mark Hübener Loss of sensory input causes rapid structural changes of inhibitory neurons in adult mouse visual cortex, Neuron, online publication, September 8 2011
Stefanie Merker | EurekAlert!
Cryo-electron microscopy achieves unprecedented resolution using new computational methods
24.03.2017 | DOE/Lawrence Berkeley National Laboratory
How cheetahs stay fit and healthy
24.03.2017 | Forschungsverbund Berlin e.V.
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
24.03.2017 | Materials Sciences
24.03.2017 | Physics and Astronomy
24.03.2017 | Physics and Astronomy