Figure 4.

Gap detection and prepulse inhibition in C57BL/6J and BALB/cByJ mice. In the top panel, baseline and startle amplitudes were collected in the presence of a 60-dB SPL broadband background noise. Baseline values provide an estimate of the force applied to the testing plate when the mouse is ambulating, grooming, and so forth (that is, not during the startle stimulus). Startle stimuli consisted of 110-dB SPL, 20-ms noise bursts. The responses to gaps were measured by comparing trials with a startle-only stimulus and trials consisting of the same startle stimulus preceded by a silent gap in the background noise. During the gap, the 60-dB background noise was turned off. Gap duration varied from 0 ms (startle-only trials) to 50 ms, and the beginning of the gap was always 100 ms before the presentation of the startle stimulus. Overall gap detection was not significantly different between C57BL/6J and BALB/cByJ mice (n = 10 per strain). In the bottom panel, prepulse inhibition (PPI) was determined by using stimuli of either 5 or 10 dB above the background noise (65 or 70 dB). Stimuli were 50 ms in duration and always began 100 ms before the presentation of the startle stimulus. PPI differed significantly (P = 0.002) between strains at 10 dB above background. For both panels, data are presented as mean ± SEM (bars).