Optokinetic responses of the crab, Carcinus to a single moving light

Abstract

Summary 1. A crab in an otherwise dark room will stabilize its eye position by reference to a single small light, so long as the illumination at the eye exceeds about 0.0003 lux.

2. The eye movements follow the movements of the light.

3. Responses to a light moving in a horizontal plane resemble those to a striped drum, but at lower percentage following.

4. Apparent motion is an effective stimulus; with intermittent light the response is reduced. If there is a period of complete darkness after the first light the subsequent movement, when the second light comes on, is slower for longer dark periods.

5. The crab learns, after some repetitions, to discriminate between a continuous light and an intermittent one, as shown by its eventually stabilizing them at different points on its retina. Show more