Directional Selectivity

Directional selectivity refers to a neuron’s ability to produce substantially different responses for stimulus motions of different direction. A directionally selective (DS) cell will fire many spikes in response to object motion in one direction (the preferred direction) while responding weakly, if at all, for motion in the opposite (null) direction. This directional “trigger feature” is often essentially independent of the contrast, contrast polarity, color, shape, or speed of the moving object. Cells displaying directional selectivity are found in the retinas and visual cortices of all the major vertebrate classes. These neurons support a host of visual tasks, ranging from motion perception, image segregation, and deblurring to the control of eye movements. The extraction of direction of motion is so crucial for vision that it is the first motion-related variable encoded in the visual pathway.