Attentive Perception Can Diminish Vagal Inhibition

Abstract

A systematic decrease in heart rate when anticipating an important stimulus or when preparing to react is called anticipatory bradycardia. Numerous studies have shown that the initiation of motor activity prompts the termination of anticipatory bradycardia in reaction time tasks. However, in experiments with procedures based on more complex reactions, the termination of anticipatory bradycardia is delayed until later cardiac cycles. This unexpected effect may be attributed to perceptual processes that are engaged in the feedback mechanism essential for effectiveness in prolonged and complex motor reactions. The experiment presented in this article was carried out to verify the hypothesis that the initiation of a motor reaction, when processed simultaneously with sustained attentive perception, does not evoke acceleration of heart rate. The experimental task was a simulated shooting at a moving target. The procedure in the experimental group induced participants to attentively observe events before and after the required reaction, whereas in the control group, attentive perception of task events after the reaction was not possible. The expected pattern of heart-rate changes appeared in the experimental group. During the initial block of trials, the initiation of the motor reaction did not evoke immediate termination of anticipatory bradycardia. During later trials in the experimental group and during all trials in the control group, heart-rate changes were completely typical - heart rate increased after the motor reaction began. The results show that attentive perception engaged immediately after the initiation of motor activity can affect the pattern of phasic heart-rate changes observed during typical reaction time tasks. Additionally, the difference between the patterns characteristic of the initial and later trials suggests possible competition between the neuronal influences that modulate heart rate.