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When cells grow and divide, they come into contact with other cells. This happens not only during development and regeneration and after injury, but also during cancer growth and the formation of metastases. When cells come into contact with each other in this way, information is exchanged by proteins, which are embedded in the cell membranes and form tight lock-and-key complexes with each other. These connections must be severed if the cells want to transmit a repulsion signal. It appears that the fastest way to do this is for the cells to engulf the protein complex from the membrane of the neighbouring cell. Scientists from the Max Planck Institute of Neurobiology in Martinsried have now identified the molecules that control this process.

Development is an extremely rapid process. Increasing numbers of cells are formed which must find their correct position in the body, clearly demarcate themselves from each other to form tissue, or – as is the case in the nervous system – establish contact with partner cells in remote locations. “The crowding is accompanied by orderly pushing and shoving,” says Rüdiger Klein, whose Department at the Max Planck Institute of Neurobiology studies how cells get their bearings. “A popular way for one cell to show another which direction to take is for it to repel the other cell following brief contact.” According to the scientists’ observations, the cells do not exactly treat each other with kid gloves and even go so far as to engulf entire pieces from the membranes of other cells. More

The adult brain has learned to calculate an image of its environment from sensory information. If the input signals change, however, even the adult brain is able to adapt − and, ideally, to return to its original activity patterns once the perturbation has ceased. Scientists at the Max Planck Institute of Neurobiology in Martinsried have now shown in mice that this ability is due to the properties of individual neurons. Their findings demonstrate that individual cells adjust strongly to changes in the environment but after the environment returns to its original state it is again the individual neurons which reassume their initial response properties. This could explain why despite substantial plasticity the perception in the adult brain is rather stable and why the brain does not have to continuously relearn everything.

Everything we know about our environment is based on calculations in our brain. Whereas a child's brain first has to learn the rules that govern the environment, the adult brain knows what to expect and, for the most part, processes environmental stimuli in a stable manner. Yet even the adult brain is able to respond to changes, to form new memories and to learn. Research in recent years has shown that changes to the connections between neurons form the basis of this plasticity. But, how can the brain continually change its connections and learn new things without jeopardizing its stable representation of the environment? Neurobiologists in the Department of Tobias Bonhoeffer in Martinsried have now addressed this fundamental question and looked at the interplay between plasticity and stability.

The scientists studied the stability of the processing of sensations in the visual cortex of the mouse. It has been known for about 50 years that when one eye is temporarily closed, the region of the brain responsive to that eye increasingly becomes responsive to signals from the other eye that is still open. This insight has been important to optimize the use of eye patches in children with a squint. “Thanks to new genetically encoded indicators, it has recently become possible to observe reliably the activity of individual neurons over long periods of time,” says Tobias Rose, the lead author of the study. “With a few additional improvements, we were able to show for the first time what happens in the brain on the single-cell level when such environmental changes occur.”

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Computation of motion by T4 cells in the fly brain is more complex than previously believed. As indicated by their name, photoreceptor cells in the eye respond to light: is an image point bright or dark? They do not indicate the direction of a movement. This perception only arises in the brain through the comparative computations of light signals coming from adjacent image points. Engineers, physicists and neurobiologists have been debating the exact nature of these computations for around 50 years.
Scientists from the Max Planck Institute of Neurobiology have now combined two theories about these computations, which were previously considered to be alternative hypotheses – and discovered that they are carried out in a single neuron.Flies are usually very difficult to catch. No wonder – they invest around ten percent of their brain in the detection and processing of image motion. For the fly, a hand approaches in slow motion and the fly’s evasive manoeuvre has long been triggered before any real danger arises. Scientists have been researching for decades how the fly brain can perceive and process movements so quickly and accurately. “Our goal is slowly coming into view, and we are close to completely decoding the neuronal circuit of motion perception in the fly,” says Alexander Borst, who has been working on this problem with his Department at the Max Planck Institute of Neurobiology for quite some time. The scientists have now come one step closer to the answer: They have provided experimental data that combine two theories previously considered as alternatives.  More