Protection from habituation by lateral inhibition

HABITUATION, or response decrement, functions to reduce an animal's responsiveness to maintained or frequently repeated stimuli, while ensuring high responsiveness to novel stimuli. Under some circumstances, however, habituation is inappropriate, in response to sensory afference caused by an animal's own activities, for example. Mechanisms for protection from habituation under such circumstances are likely to be common. Here we show, in locust movement detector (MD) neurones, that whereas habituation is rapid in response to repeated small field movements it is absent in response to maintained whole field movements. Prolonged whole field movements do not therefore reduce the responsiveness of the MD neurones to subsequent small field movements. Protection from habituation is achieved by lateral inhibition which acts prior to the site of response decrement to suppress the response to whole field stimuli.