Attentional modulation of short- and long-lead-interval modification of the acoustic startle eyeblink response: comparing auditory and visual prestimuli.

Studies in our laboratory have shown that modification of startle by lead stimuli with short- and long-lead-intervals is modulated by stimulus significance. The significant stimulus in a tone duration judgement task generates enhanced short-lead-interval startle inhibition as well as pronounced long-lead-interval startle facilitation. The present study was designed to compare tones with simple visual stimuli as lead stimuli in a counterbalanced within-subjects design (Experiment I) or between-subjects design (Experiment II). The results show that auditory compared to visual lead stimuli generate more short-lead-interval inhibition but comparable amounts of long-lead-interval startle facilitation, which was significantly enhanced on to-be-attended trials independent of sensory modality. The attentional manipulation did not yield short-lead-interval effects in Experiment I, but previously reported attention effects were replicated in Experiment II. The results suggest early modality effects on startle modification, reflected by the differing levels of inhibition. Late effects of both modality and attention, however, seem to reflect a sensory modality independent process in startle modification.