The article presents a study which examines the significance of active dendritic processing to neuronal computations in the visual system. The action of the the visual system. direction-selective retinal ganglion cells (DSGCs) when visual stimuli move across their receptive field in a particular direction is cited. It is inferred that active dendritic processing is an important component of neuronal computations in the visual system, both in the primary visual cortex and in the retina.