THE EFFECTS OF PREPULSE-BLINK REFLEX TRIAL REPETITION AND PREPULSE CHANGE ON BLINK REFLEX MODIFICATION AT SHORT AND LONG LEAD INTERVALS

Prepulse inhibition and facilitation of the blink reflex are said to r eflect different responses elicited by the lead stimulus, transient de tection and orienting response respectively. Two experiments investiga ted the effects of trial repetition and lead stimulus change on blink modification. It was hypothesized that these manipulations will affect orienting and thus blink facilitation to a greater extent than they w ill affect transient detection and thus blink inhibition. In Experimen t 1 (N = 64), subjects were trained with a sequence of 12 lead stimulu s and 12 blink stimulus alone presentations, and 24 lead stimulus-blin k stimulus pairings. Lead interval was 120 ms for 12 of the trials and 2000 ms for the other 12. For half the subjects this sequence was fol lowed by a change in pitch of the lead stimulus. In Experiment 2 (N = 64), subjects were trained with a sequence of 36 blink alone stimuli a nd 36 lead stimulus-blink stimulus pairings. The lead interval was 120 ms for half the subjects and 2000 ms for the other half. The pitch of the lead stimulus on prestimulus trials 31-33 was changed for half th e subjects in each group. In both experiments, the amount of blink inh ibition decreased during training whereas the amount of blink facilita tion remained unchanged. Lead stimulus change had no effect on blink m odification in either experiment although it resulted in enhanced skin conductance responses and greater heart rate deceleration in Experime nt 2. The present results are not consistent with the notion that blin k facilitation is linked to orienting whereas blink inhibition reflect s a transient detection mechanism. (C) 1998 Elsevier Science B.V.