Evoked heart rate and blood pressure in an S1-S2 paradigm

Phasic changes in heart rate (HR) and blood pressure (BP) in an S1-S2 paradigm were studied in three experiments. In each experiment, a memory search task was performed at S1. The outcome of this task indicated whether a fast or a delayed response had to be given after S2. Besides this response instruction, there were two other task manipulations: in one experiment the memory load at S1 was varied, whereas in each experiment a different kind of performance feedback was given. Both HR and BP showed a triphasic pattern, consisting of an initial decrease, followed by an increase and another decrease. The BP patterns were quite consistent, and delayed a few seconds relative to the HR pattern. The memory load manipulation at S1 showed that the changes early in the S1-S2 interval (initial decrease and subsequent increase) reflect the processing of S1. The effects of response instruction showed that the second HR deceleration, and the subsequent BP decrease, reflect the preparation of the motor response. In Experiment 2 the level of the evoked HR and BP pattern was shifted as a function of the type of reward (a bonus or noise).