The startle response as an indicator of temporal summation

Abstract

The present study assessed temporal summation of transient and sustained stimuli in the startle eyeblink response system. In two experiments, adult subjects received 95-dB(A), fast-rising broadband noise bursts of two types: (1) single stimuli varying in duration from 20 to 100 msec (Experiment 1) or 30 to 55 msec (Experiment 2) and (2) pairs of 3-msec bursts presented at interpulse intervals corresponding to the single stimulus durations. In addition, a single 3-msec pulse was used as an anchor point for both stimulus types. Though the temporal functions depended on whether startle amplitude or probability was assessed, both measures showed that temporal summation was similar for sustained stimuli and pulse pairs up to about 40 to 50 msec. Beyond this point, single stimuli maintained responding to 100 msec, whereas the second pulse of the pair quickly lost its effect. The results indicate that, although startle is influenced by summation of the sustained aspects of a stimulus, summation of transients produces an equivalent effect and does so with more acoustic efficiency (requires less energy). Response latency measures showed no significant summation with paired pulses, and only a narrow summation window for single stimuli. Thus, differential summation of sustained and transient information is demonstrated by all three response measures, but in different ways. © 1986 Psychonomic Society, Inc.