Scientists discover the transmission used by zebrafish to change to another gear
As we walk along a street, we can stroll at a leisurely pace, walk quickly, or run. The various leg movements needed to do this are controlled by special neuron bundles in the spinal cord. It is not quite clear how these central pattern generators know how quickly the legs are to be moved.
An international team working with scientists from Harvard University and the Max Planck Institute of Neurobiology in Martinsried has now discovered individual neurons in the brain of zebrafish larvae that control the animals' swimming speed. Human movements are also controlled by central pattern generators. The results represent an important step in gaining a better understanding of how rhythmic movements are modulated.
As young children, we learn how to place one foot in front of the other at a steady pace. Once this has been learned, small bundles of neurons in the spinal cord - the central pattern generators (CPG) - ensure that this sequence happens almost automatically: we do not need to think about when and how far away we should place our foot down when we take each step. Once they are operational, the CPG neurons do not need any further stimulus to transmit their impulses. But how are these cells stimulated, and how does the brain tell them how quickly the legs need to be moved?
Ruben Portugues and his colleagues have studied zebrafish larvae to investigate how the brain and the CPGs are connected. The animals use various methods to increase their speed: they can beat their tails for longer periods of time, move the tail to and fro more vigorously, reduce the time between periods of tail movements such that these periods called bouts happen more frequently or switch to a completely different movement rhythm or gait - like a horse that changes from a trot to a gallop.
To understand how the brain triggers these various types of swimming movements, the neurobiologists concentrated on a group of around 20 neurons which send out their extensions from the midbrain to the spinal cord. The scientists already knew that the cells in this nMLF region are active during swimming. They were now able to show that stimulating these cells triggered swimming movements. As the researchers now report in the journal Neuron, the cells in the central pattern generator receive the initial stimulus for a movement from neurons in the nMLF region. They also discovered that it is almost impossible for the fish to regulate their swimming speed if four particular nMLF cells are switched off.
Calcium-sensitive dyes can be used to image neuronal activity. As zebrafish larvae are transparent, the scientists were able to observe the activity of individual nMLF cells directly through the microscope. "It was especially exciting when the animals changed their speed," reports Ruben Portugues, who was recently appointed Leader of a Research Group at the Max Planck Institute of Neurobiology. "We had actually expected that more nMLF cells would simply be activated simultaneously to enable the fish to swim faster."
Instead, the scientists discovered that neurons which were already active became even more active when swimming faster. "We don't yet know the details of how a higher level of activity leads to faster movements," says Portugues. However, the scientists can demonstrate that individual nMLF cells, known as MeLR cells, control the length of swimming periods and MeLc cells, as they are known, control the frequency to the tail beating. To date, scientists were aware of the nMLF region and its cells, but nobody knew what they control or how they do it. "Now that we have found the transmission, as it were, for the swimming movements, the next question to be answered is how and where the brain decides what gear it wants to engage," says Ruben Portugues, summing up the next challenge.
Dr. Stefanie Merker | Max-Planck-Institute
Atomic-level motion may drive bacteria's ability to evade immune system defenses
24.04.2017 | Indiana University
Two-dimensional melting of hard spheres experimentally unravelled after 60 years
24.04.2017 | University of Oxford
More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.
Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...
Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.
"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
20.04.2017 | Event News
18.04.2017 | Event News
03.04.2017 | Event News
24.04.2017 | Physics and Astronomy
24.04.2017 | Materials Sciences
24.04.2017 | Life Sciences