Searching for mechanisms of retinal direction selectivity

A classic example of a complicated neurocomputation carried out by a relatively simple neuronal circuitry is that some mammalian retinal ganglion cells respond selectively to direction of motion. Search for the mechanisms of direction selectivity in the mammalian retina started some 35 years ago. It has been shown that direction selectivity is caused by an asymmetrical inhibition induced by GABA acting on GABAA receptors. However, the physical circuitry underlining this computation is still not clear. A few recent breakthroughs provide important evidence for the sites where the computation takes place.