Recognising movement and its direction is one of the first and most important processing steps in any visual system. By this way, nearby predators or prey can be detected and even one's own movements are controlled. More than fifty years ago, a mathematical model predicted how elementary motion detectors must be structured in the brain. However, which nerve cells perform this job and how they are actually connected remained a mystery. Scientists at the Max Planck Institute of Neurobiology in Martinsried have now come one crucial step closer to this "holy grail of motion vision": They identified the cells that represent these so-called "elementary motion detectors" in the fruit fly brain. The results show that motion of an observed object is processed in two separate pathways. In each pathway, motion information is processed independently of one another and sorted according to its direction.
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