Startle habituation in rats after lesions in the brachium of the inferior colliculus.

Bilateral interruption of the primary ascending auditory pathway at the level of the brachium of the inferior colliculus (BIC) did not affect short- or long-term habituation of the startle response provoked by auditory stimuli. Animals with BIC lesions and control animals exhibited comparable habituation following manipulations of stimulus intensity, inter-stimulus interval, and intensity of background noise, although animals with lesions in the BIC were more responsive than controls to auditory stimuli and to tactile stimuli. The integrity of the primary auditory pathway above the inferior colliculus is not necessary for short- or long-term habituation of the acoustic startle response.