Instrumental conditioning of human heart rate during free and controlled respiration.

The effect of respiratory constraint on heart rate control was assessed in a biofeedback situation with feedback consisting of changes in both illumination level and intensity of pre-recorded baby's cry. Subjects were reinforced for alternately increasing and decreasing heart rate on each of seven days during which respiration was unconstrained (Phase 1). This phase was followed by eight days when respiration was constrained during training sessions with a control respirator (Phase 2). Seven additional days of training followed in the unconstrained situation (Phase 3). Results indicate that the control of heart rate in biofeedback situations is very closely related to respiratory and other somatic activity. The implication of these findings for the field of visceral control is discussed.