Reflexes Inhibited by a Prepulse Intensity of Startle Stimulus and Prepulse Across Onset Intervals

: Prepulse inhibition refers to the inhibition of the startle reflexes by a weak stimulus (prepulse) that precedes a strong startle stimulus (pulse). Previous findings suggest that prepulse intensity affects prepulse inhibition amplitude and that prepulse inhibition amplitudes vary across onset intervals between the prepulse and pulse. However, evidence regarding the effect of startle stimulus intensity is still inconclusive, especially due to variations between prepulse inhibition scores calculated by using percentage-type and difference-type formulas. Moreover, the combined effect of startle stimulus and prepulse intensities across onset intervals remains poorly understood. The present study investigated the combined effect as well as the influence of startle response amplitudes on the formulae used for the calculation. The results suggest that startle stimulus intensity could potentially affect results of percentage-type formulae for calculating prepulse inhibition over a wide range of lead intervals. Furthermore, the results demonstrated that a combination of strong startle stimulus intensities and weak prepulse intensities could not induce prepulse inhibition at long onset intervals (1000 ms and 2000 ms).