In a tight spot

Being constantly flooded by a mass of stimuli, it is impossible for us to react to all of them. The same holds true for a little fish. Which stimuli should it pay attention to and which not? Scientists at the Max Planck Institute of Neurobiology have now deciphered the neuronal circuit that zebrafish use to prioritize visual stimuli. Surrounded by predators, a fish can thus choose its escape route from this predicament.

Even though we are not exposed to predators, we still have to decide which stimuli we pay attention to – for example, when crossing a street. Which cars should we avoid, which ones can we ignore? "The processes in the brain and the circuits that lead to this so-called selective attention are largely unexplored," explains Miguel Fernandes, a postdoctoral researcher in Herwig Baier's department. "But if we understand this in a simple animal model like the zebrafish, it can give us fundamental insights into decision-making mechanisms in humans." For this reason, Miguel Fernandes and his colleagues studied the behavior of zebrafish in the predicament described above: Using virtual reality, the team simulated two predators approaching a fish from the left and right at the same speed. In most cases, the fish focused on one of the two predators and fled in the opposite direction. They thus integrated only one, the so-called "winner stimulus", into their escape route (winner-take-all strategy).

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