Lead-stimulation effects of human cardiac orienting and blink reflexes.

Innocuous prestimulation can inhibit or facilitate a startle reflex in lower animals, depending on its lead time and on whether it is dircrete or continues throughout the lead interval. Similar effects of lead stimulation on the unconditioned blink reflex were found in human subjects, but human subjects also showed an effect not seen in lower animals. Under conditions of temporal and stimulus uncertainty, the presentation of discrete stimuli at lead times that have no effect in rats produced blink facilitation as well as pronounced cardiac decelerations during the lead interval in man. The article suggests that this effect might be mediated by an attentional process and that it could be dissociated from effects produced by a classical arousal mechanism.