Heartfelt choices: The influence of cardiac phase on free-choice actions

The influence of cardiac phases on cognitive and sensorimotor functions is noteworthy. Specifically, during systole, as opposed to diastole, there is an observed enhancement in tasks demanding the suppression of instructed responses. This suggests that systole contributes to inhibitory control in motor functions. However, the extent to which systolic inhibition is significant in volitional free-choice actions, such as choosing to execute or refrain from a cue-initiated response, remains to be clarified. To fill this gap in the current literature, the purpose of this study was to test whether during the systole phase, compared with the diastole phase, the tendency to enact volitional actions decreased due to the systolic inhibitory effect. We used a modified version of the Go/No-Go task with an added condition for volitional free-choice actions, where participants could decide whether to respond or not, to test whether systolic inhibition could affect the volitional decision to act. The results showed that participants' responses were less frequent in systole than in diastole in the volitional action condition. Then, to test the robustness of the cardiac effect on volitional actions, we used two established manipulations: the Straw Breathing Manipulation and the Cold Pressor Test, which were able to induce anxiety and increase the heart rate, respectively. Results showed that the systole/diastole difference in the number of volitional action trials in which participants decided to respond tended to remain the same despite all manipulations. Overall, our results provide convergent evidence for the effect of the heart on the decision to act, an effect that appears independent of manipulations of both the physiological and psychological state of the individual.