Habituation: a model phenomenon for the study of neuronal substrates of behavior.

The recent habituation literature is reviewed with emphasis on neurophysiological studies. The hindlimb flexion reflex of the acute spinal cat is used as a model system for analysis of the neuronal mechanisms involved in habituation and sensitization (i.e., dishabituation). Habituation of this response is demonstrated to follow the same 9 parametric relations for stimulus and training variables characteristic of behavioral response habituation in the intact organism. Habituation and sensitization appear to be central neural processes and probably do not involve presynaptic or postsynaptic inhibition. It is suggested that they may result from the interaction of neural processes resembling "polysynaptic low-frequency depression," and "facilitatory afterdischarge." "Membrane desensitization" may play a role in long-lasting habituation.