The eye of a zebrafish larva can already distinguish between prey and predator
Red or green? Small or large? Fast or slow? Humans and animals rely on their visual organs to classify objects in their environment. Decisions about how we best respond to moving objects in our environment are often made very quickly and unconsciously. The size of a moving object is obviously an important criterion.
The rapid speed of a response suggests that specialised neural circuits in the visual system are responsible for recognising important object properties. If they are activated, they trigger the "fight" or "flight" signal in the brain. Scientists at the Max Planck Institute for Medical Research in Heidelberg have now shed light on how such circuits, which are likely to be crucial in classifying objects by size, function in the brain of the zebrafish larva.
How does the brain decide which things in our complex environment require an immediate response from us? A key question in the animal kingdom is: "Is the object moving in my environment prey or predator?" - a question that requires a quick answer in an emergency. Evidently, the visual system manages to detect objects from the constantly changing distribution of light stimuli on the retina based on simple criteria and, if necessary, mobilise a rapid response directly. The basic mechanisms of object classification can be studied using zebrafish larva as the model system.
The larva's well-developed visual system allows it to catch small prey and avoid larger objects. The decision about whether the larva approaches or avoids the object is made on the basis of size. Researchers working with Johann Bollmann at the Max Planck Institute in Heidelberg have now been able to demonstrate that small and large stimuli, which trigger swimming movements in different directions, generate neural activity in neighbouring but different circuits in the fish's brain. The behaviour-related distinction in size thus begins in the ganglion cells of the eye.
The retina in the eye contains a variety of different ganglion cells which respond specifically to colour, size, movement or contrast, for example. However, little is understood about how these different messages travel via the optic nerve to the brain and are processed. The researchers were now able to identify such cells in a central area of the fish's brain - the tectum. These cells respond specifically to those object sizes that correspond to a small prey or a large troublemaker in the world of the zebrafish larva.
It turns out that the nerve endings of ganglion cells, which project into the tectum, respond differently to object size. Other cell types downstream in the tectum distinguish between small and large objects on the zebrafish's magnitude scale in their activity patterns, depending on the layer in which they receive their synaptic inputs.
"This suggests that the size classification process begins in the retina of the eye to subsequently classify the object that is seen in the tectum into the categories of 'small enough to count as prey' or 'sufficiently large to watch out for'. The fish larva then adapts its behaviour accordingly," says Johann Bollmann from the Max Planck Institute for Medical Research. The brains of mammals contain very similar structures that are crucially involved in the visual control of such targeted movements. This suggests that the functions of detecting objects and controlling actions are resolved in a similar way as they are in the small brain of the fish larva.
Johann H. Bollmann | Max-Planck-Institute
A Map of the Cell’s Power Station
18.08.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau
On the way to developing a new active ingredient against chronic infections
18.08.2017 | Deutsches Zentrum für Infektionsforschung
Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.
As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...
Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.
Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...
For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.
While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...
An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.
The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...
A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.
Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...
16.08.2017 | Event News
04.08.2017 | Event News
26.07.2017 | Event News
18.08.2017 | Life Sciences
18.08.2017 | Physics and Astronomy
18.08.2017 | Materials Sciences