How the heart shapes the mind: The role of cardiac interoception in the interaction between bodily reactions and self-related thoughts

Our thoughts often drift away from the tasks at hand. Various factors influence this phenomenon, including changes in the external environment, individual cognitive characteristics, and fluctuations in bodily reactions. This study investigated the relationship between fluctuations in cardiac activity and thought state transitions, focusing on individual differences such as cardiac interoception. First, the heartbeat counting task was conducted as an index of interoceptive accuracy. Participants then completed an auditory attention task with simultaneous electrocardiogram monitoring, during which they periodically reported on their thoughts. We estimated trial-by-trial thought states in a data-driven manner and examined the interplay among the current thought state, cardiac activity, and individual cardiac interoceptive accuracy. The results revealed that for individuals with high cardiac interoceptive accuracy, the persistence of self-related thought states was associated with concurrent heart rate acceleration. Furthermore, participants with higher depressive tendencies and interoceptive accuracy exhibited an increased likelihood of transitioning to self-related states when experiencing decreased heart rate during task-focused states. These findings suggest that interoception plays a dynamic role in shaping consciousness; the accurate detection of physiological arousal co-occurring with a specific thought might amplify that thought's salience, thereby influencing its persistence. This study provides new insights into the cognitive and physiological mechanisms underlying the dynamics of spontaneous thought.