Heart-rate change as a component of the orienting response.

Both Sokolov and the Laceys have proposed that autonomic feedback to central neural structures amplifies or reduces the effects of stimulation. Lacey and Lacey distinguished between the effects of feedback from the cardiovascular system and from other autonomic systems and suggested, specifically, that heart-rate (HR) acceleration should be associated with stimulus "rejection" and HR deceleration with stimulus enhancement. This appeared to be contradicted by evidence that HR increased with the orienting reflex whose function, according to Sokolov, is the enhancement of stimulus reception. However, when studies using simple "nonsignal" stimuli were reviewed, it was found that the criteria identifying an orienting reflex were satisfied by responses of HR deceleration and that instances of HR acceleration probably reflected a "defense," "startle," or "acoustic-cardiac" response. (2 p. ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)