Conditioning in the Cardiovascular System

Abstract

Pulse transit time (PTT) refers to the time taken by the arterial pressure pulse to travel from one point to another more peripheral site on the same artery. PTT is of some interest to psychologists since it reflects changes in arterial elasticity and is correlated with changes in diastolic blood pressure. The primary concern of this thesis was to investigate the classical conditioning of PTT. As an initial step, Experiments 1, 2 and 3 describe the development of an automatic recording system which provides beat by beat samples of PTT measured between two peripheral pulses and from the foot of the pulse wave. A series of experiments used this measurement technique to record PTT changes in response to a differential classical conditioning procedure with a variety of unconditioned stimuli. Concomitant changes in other cardiovascular responses were also recorded. In Experiment 4, with the cold pressor as UCS, there were conditioned decreases in PTT and increases in vasoconstriction and ECG-initiated transit time (ECG-TT). Experiment 6 investigated conditioned responding with an increased number of trials and a problem-solving UCS.A conditioned decrease in both PTT and inter-beat interval-(IBI) were observed, and a consistent biphasic beat effect was evident for both responses. The conditioned decrease from baseline was attenuated in later trials, concomitant with a tonic increase in PTT and IBI and attenuation of the UCR. Experiment 7 varied the procedure used in Experiment 6 by changing the stimulus used as the CS and the ISI length. While neither influenced PTT CR development, there was a greater conditioned decrease in IBI to a neutral than a phobic stimulus. The attenuation of the UCR was found to be a function of within-session tonic changes rather than habituation effects. Experiment 8 used a video game as the UCS and demonstrated a conditioned PTT decrease from baseline and differential PTT responding. The PTT CR persisted across twenty acquisition trials. PTT, IBI and ECG-TT all showed a consistent biphasic response. Experiment 9 replicated the procedure of Experiment 8 but used extended acquisition and an extinction phase. A conditioned decrease from baseline occurred for PTT and IBI across the forty trials. Differential responding was evident for PTT, IBI and ECG-TT. The biphasic beat effects found in Experiment 8 were replicated and persisted during initial extinction trials.