Heart-rate decelerative Pavlovian conditioning with tilt as UCS: towards behavioural control of cardiac dysfunction.

As part of a programme the ultimate goal of which is to teach behavioural control of stress-induced maladaptive cardiac accelerations through Pavlovian decelerative conditioning, this study was directed at examining the feasibility of using tilting of the body from a head-up to a head-down position as the unconditional stimulus (UCS) to elicit phasic cardiac deceleration as the unconditional response (UCR). Experiment I assessed the reflexive features of the cardiac response to 32 tilt UCS trials delivered at mean intervals of 75 sec. The results yielded a large-magnitude (over 30 BsPM) cardiac decelerative UCR with fast recruitment and complete resistance to habituation. Experiment II examined the feasibility of using the tilt UCS to demonstrate associative control over decelerative responding to a tone as the conditional stimulus (CS). Relative to a control 'backward' UCS-CS group with an interstimulus interval (ISI) of 14.5 sec, a 0.5 sec ISI CS-UCS experimental group demonstrated both orderly acquisition and extinction performance. The magnitude of the conditional deceleration of some 4 BsPM is greater than the extent of control generally achieved with biofeedback, but still constitutes a problem for theoretical accounts of classical conditioning framed in terms of stimulus substitution, and is still only of borderline clinical significance.