From vision to action
Zebrafish larvae are effective hunters of even smaller organisms. When a single-celled paramaecium swims into view, the animal turns towards it, pursues it and captures it by sucking it into his mouth. We recently discovered that a moving dot that is displayed on a miniature computer screen is able to elicit a sequence of movements that resembles prey capture. The animal swims toward the wiggling dot on the screen in front of it, in an apparent attempt to catch this “virtual prey”. However, when the dot on the screen is not behaving like potential food but is rather expanding in size, simulating an approaching object, then the fish reacts by making an escape turn to avoid the expected collision. Thus, specific visual stimulus configurations release particular behaviors. We recently found that these stimuli activate different sets of retinal ganglion cells, which project into distinct areas of the brain. How does the brain activate the appropriate motor programs?