The present study evaluated the ability of a weak electrical
prepulse to modify startle caused by a more intense shock. Painful
electrical shocks (150 V, 0.5 ms duration) were presented to
the upper arm of college student participants, preceded on some
trials by a weaker shock (0.5 ms duration, at perceptual threshold)
at the same location. Intense shocks elicited eyeblink reflexes,
and these eyeblinks were inhibited by weak electrical prepulses.
These data suggest that the inclusion of prepulses immediately
preceding painful therapeutic shocks, such as those generated
by an implanted cardioverter-defibrillator, might be capable
of reducing the startle response generated by that therapeutic
shock.