title: Habituation of the acoustic startle response in rats after lesions in the mesencephalic reticular formation or in the inferior colliculus.
abstract: Extensive damage to the mesencephalic reticular formation (MRF) in rats altered long-term habituation of the acoustic startle response without disrupting short-term habituation. The MRF lesions did not alter initial startle amplitudes, but the animals with lesions were unable to attain as low a long-term asymptote of habituation as could control animals. Subsequent manipulation of stimulus intensity and interstimulus interval revealed no differences in short-term habituation between the two groups. Large lesions to the inferior colliculus (IC) did not disrupt long-term habituation of the acoustic startle response, but these animals were unable to suppress responding as much as controls to intense stimuli presented rapidly. The deficits in long-term habituation following MRF lesions suggested a disruption of an extrinsic, inhibitory mechanism of habituation. The deficits following IC lesions could be due either to a disruption of a short-term habituation mechanism or to an increase in response sensitization produced by the lesions.
mesh_terms: D000161:Acoustic Stimulation; D000818:Animals; D001931:Brain Mapping; D006185:Habituation, Psychophysiologic / Q000502:physiology*; D007245:Inferior Colliculi / Q000502:physiology*; D008297:Male; D008636:Mesencephalon / Q000502:physiology*; D051381:Rats; D013216:Reflex, Startle / Q000502:physiology*