The acoustic startle reflex and its modulation: effects of age and gender in humans.

The acoustic startle reflex and its modulation by prepulse inhibition (PPI) and habituation are used in many studies in different fields of neuropsychiatric research. The aim of this study was to examine the effects of age and gender on PPI, startle magnitude, and habituation in healthy human volunteers. Twenty-seven male and 28 female participants of four different age groups (range: 20-60 years) were investigated in an acoustic startle paradigm using a startle stimulus of 115 dB and a prepulse of 86 dB (16 dB over the white noise background) with five different lead intervals (30, 60, 120, 240, and 2000 ms). Seventeen males and 16 female participants were tested three times at monthly intervals. Aged participants showed significantly lower startle magnitude and significantly more habituation than younger participants, but there was no effect of age on PPI or prepulse facilitation. Moreover, there were no effects of gender on startle magnitude, PPI, prepulse facilitation, or habituation measures. Healthy males and females exhibited stable startle magnitudes and PPI across sessions. The results demonstrated that PPI and startle are reliable measures of sensory information processing in both genders and that startle magnitude and habituation are age-dependent measures.