Attentional modulation of prepulse inhibition: a new startle paradigm.

There is increasing evidence for an influence of directed attention on prepulse inhibition (PPI) of the acoustic startle reflex. However, the existing paradigms for the assessment of this effect have methodological problems and pitfalls. In particular, most previous studies used a paradigm which directed the attention of subjects to the prepulse only. In the present study, we used a modified paradigm which directed the attention of the subjects both to the prepulse and the pulse. Twenty healthy male subjects were instructed trial by trial either to relax or to attend to the startle stimulus and decide whether it was a 'simple' (prepulse alone or pulse alone) or a 'composite' trial (pulse plus a prepulse or postpulse). Directed attention enhanced PPI at the lead interval of 240 ms, but not at the lead interval of 100 ms. This finding is in line with the idea that attention contributes to PPI when there is enough time for the attentional mechanisms to exert an influence. This new paradigm offers a valuable tool for the study of attentional modulation of sensorimotor gating in humans.