Neurons are not randomly arranged in the human brain. In the cortex, they are organized in interconnected clusters with high intrinsic connectivity. This modular connectivity structure, in which clusters eventually serve as functional units, is formed in early phases of development. The underlying self-organization process is regulated by neuronal activity but the detailed mechanisms are still poorly understood.
Based on in vitro studies and computational modeling, neuroscientists Dr. Samora Okujeni and Prof. Dr. Ulrich Egert from the Bernstein Center Freiburg now made an important contribution to the understanding of brain networks and their development: in their current study, they show how neuronal outgrowth and migration interact in shaping network architecture and the degree of modularity in mature networks. Their findings have now been published in the open access online journal eLife.
Neurons are sociable cells that, on the long run, die in isolation. During development, they therefore grow out cellular processes, termed neurites, to establish synaptic connections with other neurons. Once they receive sufficient or too much synaptic input, however, they stop growing or shrink.
By this, neurons avoid long-term over-excitation. It is widely assumed among researchers that neuronal growth is hereby controlled to stabilize neuronal activity at a specific target level.
Yet, to increase the probability of connections, neurons cannot only grow out their neurites but are also able to migrate towards other neurons. “In computer simulations we show that migration and neurite outgrowth may interact to shape specific mesoscale network architectures” says Samora Okujeni.
The interaction regulates the relation between local connectivity within clusters and long-range inter-cluster connectivity and thereby the degree of network modularity. “This, in turn, influences the generation and spatiotemporal patterns of spontaneous activity.” Such interdependencies may be crucial for the proper development of the cortex.
The scientists tested the model predictions experimentally by investigating how cell migration, neurite outgrowth and activity interact in developing networks of cultured rat cortical neurons. To modulate cell migration in these networks they manipulated an enzyme that is centrally involved in the regulation of the neuronal cytoskeleton. As in their simulations, cell migration and clustering likewise promoted modular connectivity in vitro.
Yet, in addition, clustering promoted activity generation and led to higher activity levels. This was inconsistent with the assumed regulation of growth to establish a common target activity level. The scientists could resolve this discrepancy:
“Cytoskeletal dynamics are not directly controlled by action potential activity but indirectly through an associated calcium influx that influences the balance between growth and degradation.” Okujeni explains. “Modularity increased the overall rate of action potentials but decreased their synchronization across the network that effectively determines the calcium influx per action potential. Given this dependence, we estimated that all network structures attain a similar target level of calcium influx during development.”
Okujeni, S., Egert, U. (2019). Self-organization of modular network architecture by activity-dependent neuronal migration and outgrowth.
Elife 8. DOI: 10.7554/eLife.47996
Learn more about Samora Okujeni’s work
Dr. Samora Okujeni
Bernstein Center Freiburg
Phone: +49 (0)761/203 - 7523
Nicolas Scherger | idw - Informationsdienst Wissenschaft
Biophysicists reveal how optogenetic tool works
29.05.2020 | Moscow Institute of Physics and Technology
Mapping immune cells in brain tumors
29.05.2020 | University of Zurich
In living cells, enzymes drive biochemical metabolic processes enabling reactions to take place efficiently. It is this very ability which allows them to be used as catalysts in biotechnology, for example to create chemical products such as pharmaceutics. Researchers now identified an enzyme that, when illuminated with blue light, becomes catalytically active and initiates a reaction that was previously unknown in enzymatics. The study was published in "Nature Communications".
Enzymes: they are the central drivers for biochemical metabolic processes in every living cell, enabling reactions to take place efficiently. It is this very...
Early detection of tumors is extremely important in treating cancer. A new technique developed by researchers at the University of California, Davis offers a significant advance in using magnetic resonance imaging to pick out even very small tumors from normal tissue. The work is published May 25 in the journal Nature Nanotechnology.
researchers at the University of California, Davis offers a significant advance in using magnetic resonance imaging to pick out even very small tumors from...
Microelectronics as a key technology enables numerous innovations in the field of intelligent medical technology. The Fraunhofer Institute for Biomedical Engineering IBMT coordinates the BMBF cooperative project "I-call" realizing the first electronic system for ultrasound-based, safe and interference-resistant data transmission between implants in the human body.
When microelectronic systems are used for medical applications, they have to meet high requirements in terms of biocompatibility, reliability, energy...
Thomas Heine, Professor of Theoretical Chemistry at TU Dresden, together with his team, first predicted a topological 2D polymer in 2019. Only one year later, an international team led by Italian researchers was able to synthesize these materials and experimentally prove their topological properties. For the renowned journal Nature Materials, this was the occasion to invite Thomas Heine to a News and Views article, which was published this week. Under the title "Making 2D Topological Polymers a reality" Prof. Heine describes how his theory became a reality.
Ultrathin materials are extremely interesting as building blocks for next generation nano electronic devices, as it is much easier to make circuits and other...
Scientists took a leukocyte as the blueprint and developed a microrobot that has the size, shape and moving capabilities of a white blood cell. Simulating a blood vessel in a laboratory setting, they succeeded in magnetically navigating the ball-shaped microroller through this dynamic and dense environment. The drug-delivery vehicle withstood the simulated blood flow, pushing the developments in targeted drug delivery a step further: inside the body, there is no better access route to all tissues and organs than the circulatory system. A robot that could actually travel through this finely woven web would revolutionize the minimally-invasive treatment of illnesses.
A team of scientists from the Max Planck Institute for Intelligent Systems (MPI-IS) in Stuttgart invented a tiny microrobot that resembles a white blood cell...
19.05.2020 | Event News
07.04.2020 | Event News
06.04.2020 | Event News
29.05.2020 | Materials Sciences
29.05.2020 | Materials Sciences
29.05.2020 | Power and Electrical Engineering