Sex differences in prepulse inhibition of the acoustic startle response

The startle response is inhibited when the startle-eliciting stimulus is preceded 30–500 ms by a prepulse. This effect, known as prepulse inhibition (PPI), is believed to represent a sensorimotor gating mechanism, which protects the brain from experiencing sensory overload. PPI is disturbed in many psychiatric disorders. Within healthy populations, women show less PPI than men. This study employed a new PPI paradigm with a single prepulse or two prepulses to measure PPI in 15 men and 15 women. Startle stimuli were preceded on some trials by a single discrete prepulse with a 120-ms prepulse-to-pulse interval. On other trials, a second discrete prepulse preceded the first with 30–480-ms prepulse-to-prepulse intervals. Women showed less PPI than men with a single prepulse. PPI, however, was quantitatively identically reduced (greatest reduction when the second prepulse preceded the first with a 120-ms interval) in the two sexes by two-prepulse trials, relative to that with a single prepulse. Women showed a smooth transition from reduced PPI to an observed prepulse facilitation (PPF) with two prepulse trials. We conclude that sex difference consists in a general shift of the inhibition/facilitation curve in the direction of facilitation in women relative to men.