How the Heart Shapes the Mind: The Role of Cardiac Interoception in the Interaction between Autonomic Nervous Activity 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 responses. This study investigated the relationship between autonomic nervous fluctuations and thought state transitions, focusing on individual differences such as cardiac interoception. First, the heartbeat counting task was conducted, and the difference between the reported and actual number of heartbeats was used as an index of interoceptive accuracy. The participants then completed an auditory attention task while their cardiac activities were monitored. During the task, thought probes were randomly presented, and participants selected their thought content from eight categories and rated aspects such as task concentration and arousal. We estimated trial-by-trial thought states in a data-driven manner and examined how the current thought state, autonomic nervous activity, and individual cardiac interoceptive accuracy influenced the thought state in the next trial. The results demonstrated a strong association between higher cardiac interoceptive accuracy and the maintenance of similar states in subsequent trials when accelerated heart rates occurred during self-related thought states. Furthermore, the 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-concentrated states. These results suggest that accurately detecting heart rate changes associated with specific thought states facilitates updates in first-person conscious experience, thereby biasing the transition patterns of subsequent thought states. This study provides new insights into the cognitive and physiological mechanisms underlying the dynamics of spontaneous thought.