The brain is an extremely adaptable organ – but it is also very conservative according to scientists from the Max Planck Institute of Neurobiology in Martinsried in collaboration with colleagues from the Friedrich Miescher Institute in Basel and the Ruhr Institute Bochum.
Even when neurons in the visual cortex are cut off from their main source of information, within 48 hours their activity returns to a level similar to that prior to the disruption. Under the microscope the currently active cells light up thanks to the addition of a calcium indicator.
© MPI of Neurobiology/Hübener
The researchers succeeded in demonstrating that neurons in the brain regulate their own excitability so that the activity level in the network remains as constant as possible. Even in the event of major changes, for example the complete absence of information from a sensory organ, the almost silenced neurons re-establish levels of activity similar to their previous ones after only 48 hours. The mean activity level thus achieved is a basic prerequisite for a healthy brain and the formation of new connections between neurons – an essential capacity for regeneration following injury to the brain or a sensory organ, for example.
Neurons communicate using electrical signals. They transmit these signals to neighbouring cells via special contact points known as the synapses. When a new item of information presents for processing, the cells can develop new synaptic contacts with their neighbouring cells or strengthen existing ones. To enable forgetting, these processes are also reversible. The brain is consequently in a constant state of reorganisation, through which individual neurons are prevented from becoming either too active or too inactive. The aim is to keep the level of activity constant, as the long-term overexcitement of neurons can result in damage to the brain.
Too little activity is not good either. “The cells can only re-establish connections with their neighbours when they are ‘awake’, so to speak, that is when they display a minimum level of activity,” explains Mark Hübener, head of the recently published study. The international team of researchers succeeded in demonstrating for the first time that the brain itself compensates for massive changes in neuronal activity within a period of two days, and can return to a similar level of activity to that before the change.
Up to now, the only indication of this astonishing capacity of the brain came from cell cultures. It was also unclear as to how neurons could control their own excitability in relation to the activity of the entire network. Now, the scientists have made significant progress towards finding an answer to this question. In their study, they examined the visual cortex of mice that recently went blind. As expected, but never previously demonstrated, the activity of the neurons in this area of the brain did not fall to zero but to half of the original value. “That alone was an astonishing finding, as it shows the extent to which the visual cortex also processes information from other areas of the brain,” explains Tobias Bonhoeffer, who has been researching processes in the visual cortex at his department in the Max Planck Institute of Neurobiology for many years. “However, things really became exciting when we observed the area further over the following hours and days.”
The scientists were able, under the microscope, to witness “live” how the neurons in the visual cortex became active again. After just a few hours, they could clearly observe how the points of contact between the affected cells and neighbouring cells increased in size. When synapses get bigger, they also become stronger and signals are transmitted faster and more effectively. As a result of this intensification of the contact between the neurons, the activity of the affected network returned to its starting value after a period of between 24 and 48 hours. “To put it simply, due to the absence of visual input, the cells had less to say – but when they did say something, they said it with particular emphasis,” explains Mark Hübener.
Due to the simultaneous strengthening of all of the synapses of the affected neurons, major reductions in the neuronal activity can be normalised again with surprising speed. The relatively stable activity level thereby achieved is an essential prerequisite for maintaining a healthy, adaptable brain.
ContactDr. Stefanie Merker
Dr. Stefanie Merker | Max-Planck-Institut
Molecular Force Sensors
20.09.2017 | Max-Planck-Institut für Biochemie
Foster tadpoles trigger parental instinct in poison frogs
20.09.2017 | Veterinärmedizinische Universität Wien
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...
For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.
Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...
MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems Holding GmbH about commercial use of a multi-well tissue plate for automated and reliable tissue engineering & drug testing.
MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems...
Pathogenic bacteria are becoming resistant to common antibiotics to an ever increasing degree. One of the most difficult germs is Pseudomonas aeruginosa, a...
19.09.2017 | Event News
12.09.2017 | Event News
06.09.2017 | Event News
20.09.2017 | Life Sciences
20.09.2017 | Power and Electrical Engineering
20.09.2017 | Physics and Astronomy