Auditory and visual prepulse inhibition in mice: parametric analysis and strain comparisons.

Prepulse inhibition (PPI) is a multimodal phenomenon where the prepulse and the startling stimulus can be presented in either the same or the different sensory modalities. The aim of the present study was to characterize intramodal and cross-modal PPI in mice. We first examined the effects of varying prepulse intensity and prepulse duration on auditory and visual PPI in three inbred mouse strains C57BL/6J, 129S2 and BALB/cByJ mice. Increasing the intensity (5-15 dB above the background) and the duration (1-25 milliseconds) of the acoustic prepulse increased auditory PPI, and maximum level of inhibition was reached with each prepulse intensity at specific prepulse duration (between 5 and 15 milliseconds). Varying the intensity (30-300 lux) and the duration (1-25 milliseconds) of the light flashes had similar impact on visual PPI level (optimal durations between 1 and 10 milliseconds). There were also marked strain differences in PPI performances, with 129S2 and BALB/cByJ mice displaying the highest and the lowest scores of auditory PPI, respectively. In contrast, opposite strain ranking was obtained for visual PPI. The temporal expression of PPI was then studied in the same mouse strains using a wide range of interstimulus intervals (2-2000 milliseconds between the prepulse offset and the pulse onset). The time-course of the auditory and the visual PPI were relatively comparable (bell-shaped curve) with optimal lead-times between 10 and 100 milliseconds, but the shape of the temporal function varied between the mouse strains depending on the prepulse modality. These findings demonstrate that PPI has many physiological and genetic determinants that vary greatly across temporal and intensity domain, as well as stimulus modality.