Fig. 2.

Schematic diagram of the PPI experiment. On control trials, acoustic startle stimuli were delivered at the onset of 5- or 6-sec duration tones. On prepulse trials, acoustic startle stimuli were delivered 120 sec after the onset of the tones. Seven sec before a tone onset, the words “listen” or “ignore” were displayed on a computer monitor. On “attend” trials, subjects had to listen to the tones and report the number of short- and long-duration tones.