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Abstract

It is essential for the visual system to detect image motion and to compute its direction and speed. Information on local motion is needed to predict the trajectory of moving objects, whereas information on global motion provides important feedback about body and head movement relative to the environment. That the computation of image motion starts in the retina was discovered more than 40 years ago: when Barlow and his colleagues recorded from retinal ganglion cells in the rabbit, they found a subset of cells that fired vigorously when an object moved in a certain (preferred) direction across their receptive fields but remained silent when the object moved in the opposite (null) direction. This chapter provides an overview of these direction-selective ganglion cells and the neuronal circuitry that underlies direction selectivity in the vertebrate retina.