Human Pavlovian decelerative cardiac conditioning based on a respiratory-induced cardiac deceleration as an unconditional reflex.

This study was directed at examining the feasibility of using a respiratory-induced cardiac decelerative reflex as an unconditioned response (UCR) in a Pavlovian conditioning paradigm. Experiment I assessed the reflexive features of the cardiac response under a respiratory procedure which involved 3 sec of exhalation, 4 sec of inhalation, and then 30 sec of breath-holding (BH). The results indicated that the BH onset aspect of this respiratory cycle involved a phasic, large-magnitude cardiac deceleration (27 beats/min) with short latency, fast recruitment, and no indication of habituation over trials. Experiment II examined the feasibility of using BH onset as an unconditioned stimulus (UCS) in a Pavlovian paradigm by presenting an auditory conditional stimulus (CS) 1 sec prior to the instructed BH aspect of the respiratory cycle. A separate control condition involved presenting the CS 10 sec after BH onset which constituted a 'backward' conditioning control. The results indicated that the conditioning group displayed a significant cardiac deceleration on CS-alone test trials (under normal breathing) in contrast to the absence of such an effect for the control group. In brief, the study suggested that a decelerative conditioned response (CR) could be established by using a respiratory-induced cardiac deceleration as a Pavlovian UCS. Potential clinical applications of such a decelerative CR were noted.