Habituation and prestimulus inhibition of the auditory startle reflex in decerebrate rats

Abstract

Integrated emgs, recorded from muscles of the neck, have been used to study the auditory startle reflex in the decerebrate rat. The reflex had a mean onset latency of 11.6 msec and a mean duration of 90 msec; it was abolished by lesions in the inferior colliculus and, in some animals, lesions in the pontine or caudal mesencephalic reticular formation. It was found that the startle response, in the decerebrate animal, was habituated in a way comparable with that described in the intact animal. The size of the response was also reduced by a single preceding auditory stimulus, whether or not that stimulus was above threshold for eliciting a startle response. It therefore appears that short term habituation and prestimulus inhibition of the startle reflex are not dependent on higher regions of the central nervous system.