Key result
Cardiac defense was elicited by longer stimulus durations (500 and 1000 ms) but not affected by rise time, whereas eyeblink startle magnitude decreased with longer rise times.
Why the study?
Does varying the duration and rise time of an intense acoustic stimulus differentiate between cardiac defense and cardiac startle reflexes?
RCT (n=200)
Random allocation
No
Does varying the duration and rise time of an intense acoustic stimulus differentiate between cardiac defense and cardiac startle reflexes?
Stimulus duration, but not rise time, differentiates the cardiac defense reflex, challenging previous models of cardiac startle and defense.
Stimulus parameters may distinguish cardiac defense from startle in research; leaves open relevance to clinical cardiovascular reactivity assessment.
Rise time and duration are two parametric characteristics of the eliciting stimulus frequently used to differentiate among psychophysiological reflexes. The present research varied the duration (study 1) and rise time (study 2) of an intense acoustic stimulus to dissociate cardiac defense and cardiac startle using the eyeblink response as the external criterion of startle. In each study, 100 participants were presented with five white noise stimuli of 105 dB under one of five duration (50, 100, 250, 500, and 1000 ms) or rise time (0, 24, 48, 96, and 240 ms) conditions. Cardiac defense was affected by stimulus duration, present only in the 500- and 1000-ms conditions, but not by stimulus rise time, present in all rise time conditions. Rise time affected blink startle, but did not selectively alter the short latency accelerative component of the heart rate response, thus questioning whether it reflects startle.
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Ramírez-Uclés et al. (2005) conducted an RCT in Healthy volunteers (n=200). Intense acoustic stimulus (105 dB white noise) vs. Varying stimulus durations (50-1000 ms) and rise times (0-240 ms) was evaluated on Cardiac defense response (heart rate changes) and eyeblink startle magnitude. Cardiac defense was elicited by longer stimulus durations (500 and 1000 ms) but not affected by rise time, whereas eyeblink startle magnitude decreased with longer rise times.
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