Heart rate perception and the voluntary control of heart rate

Heart rate perception was assessed in two sets of trials by having subjects set an intermittent visual pulse to match their heart rates. Just prior to matching subjects were required to either hyperventilate, hypoventilate or breathe normally to encourage a range of cardiac levels. Preceding each set of perception trials, bidirectional heart rate control was attempted. While one group of subjects received no exteroceptive feedback throughout, the other received continuous visual heart rate feedback on the second occasion. The data provided evidence of heart rate perception (as indexed by the correlation between interbeat and interpulse intervals) in a substantial number of instances. Further, perception was reliably associated with initial externally unaided cardiac control, although only in the increase direction. However, while the introduction of feedback tended to enhance cardiac control albeit only acceleratory control, no parallel effect was observed for perception. Analysis of interbeat and interpulse intervals in the different conditions of the matching task suggested that a real discrimination was probed by the procedure employed, but implied that respiratory cues afforded the basis for discrimination.