Dictionary of Biological Psychology
(i) Perception: Adaptation is a nearly universal property of neural systems. Prolonged stimulation leads to steady decline in responsivity. Adaptation has also been demonstrated behaviourally in studies of human spatial vision and has been a key technique in developing the concept of SPATIAL FREQUENCY CHANNELS.
Exposure to a high contrast visual stimulus has been shown to lead to a number of transitory perceptual changes such as decreases in sensitivity and changes in the visual appearance of subsequently viewed patterns. Close analysis of these effects lead to the development of the multiple-channel theory of spatial vision. An unresolved issue is the exact cause of the contrast adaptation (or more precisely, HABITUATION), which may be due either to reductions in the concentration of some essential metabolite or the result of alterations in the neural organisation of visually responsive neurons.
(ii) Evolution: SPECIES tend to evolve whose individuals are well fitted to the challenges of their environment: this process is called ADAPTATION. It depends upon the existence of heritable variation between individuals, yet its mechanism—differential death—inexorably uses up this variation; see NATURAL SELECTION.
DAVID W.HEELEY AND RICHARD W.BYRNE
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