Neural adaptation

Neural adaptation or sensory adaptation is a change over time in the responsiveness of the sensory system to a constant stimulus. It is usually experienced as a change in the stimulus. For example, if one rests one's hand on a table, one immediately feels the table's surface on one's skin. Within a few seconds, however, one ceases to feel the table's surface. The sensory neurons stimulated by the table's surface respond immediately, but then respond less and less until they may not respond at all; this is neural adaptation.

More generally, neural adaptation refers to a temporary change of the neural response to a stimulus as the result of preceding stimulation. It is usually distinguished from memory, which is thought to involve a more permanent change in neural responsiveness. Some people use adaptation as an umbrella term that encompasses the neural correlates of priming and habituation. In most cases, adaptation results in a response decrease, but response facilitation does also occur.

Adaptation is considered to be the cause of perceptual phenomena like afterimages and the motion aftereffect. In the absence of fixational eye movements, visual perception may fade out or disappear due to neural adaptation. (See Adaptation (eye).)

While large mechanosensory neurons such as type I/group A&beta; will display adaptation, smaller type IV/group C nociceptive neurons do not. As a result, pain does not usually subside rapidly but persists for long periods of time, but one quickly stops receiving touch or other sensory information if surroundings remain constant.