Biology subjects

Shinagawa, K.

Publications and source records attributed to Shinagawa, K..

7 recordsLinked to original sources

bioRxiv2026

Heartbeat-Related Bodily Processing Shapes Transition Patterns in Self-Related Spontaneous Thought

Spontaneous thought changes over time, yet the moment-to-moment factors shaping these changes remain poorly understood. We examined whether heartbeat-related bodily processing, operating largely outside explicit awareness, is associated with the organization of ongoing thought. Forty adults performed an auditory attention task with intermittent thought probes in which auditory events were scheduled either 200 ms after each detected R peak (synch condition) or independently of ongoing cardiac timing (asynch condition), with occasional omissions in both conditions. Heartbeat-synchronous omissions in this paradigm have been shown to induce cardiac deceleration and modulate heartbeat-evoked potentials (HEPs). The score of the heartbeat counting task (HCT) served as a behavioral index related to cardiac interoceptive accuracy. The results showed that higher HCT score was associated with a stronger synch-asynch shift toward more self-related and less task/self-unrelated thought. HEPs showed a synch-related negative shift across several thought groups, although the magnitude of this condition effect did not reliably differ among thought groups. Overall thought-group distributions were similar across conditions, while transition analyses suggested a tendency in the synch condition toward more frequent transitions linking predominantly interoceptive stimulus-dependent thought with both on-task and self-related thought. Together, these findings suggest that heartbeat-related bodily processing may influence the organization of spontaneous thought, particularly in individuals with greater cardiac interoceptive accuracy. Bodily signals may therefore act as an automatic constraint on the ongoing stream of thought, biasing which thought contents and transitions become more likely over time.

neuroscience↗

bioRxiv2026

Autonomic and cortical responses to heartbeat-synchronous auditory omissions during an auditory attention task

Cardiovascular regulation depends on bidirectional communication between autonomic cardiac control and cardiac afferent signals ascending to the central nervous system, forming a heart-brain loop. Cardio-auditory omission paradigms provide a non-invasive way to probe this loop in humans by withholding scheduled tones within heartbeat-contingent auditory sequences and measuring the resulting autonomic cardiac and heartbeat-related cortical responses. Previous studies have shown omission-evoked cardiac deceleration and neural responses mainly in specific contexts such as passive listening or synchrony-judgement tasks. The present study examined whether these responses also occur under the more general condition of active responses to external stimuli. We tested 40 adults in an auditory detection task in which tones were presented either 200 ms after the ECG R-peak (synch) or at pseudo-random intervals matched to each participants resting heart rate (asynch). A five-minute no-stimulation resting recording was used to generate the asynch sequence and served as the resting comparison condition. In both auditory conditions, 10% of scheduled tones were omitted, yielding synch and asynch omissions. Heartbeat-synchronous omissions induced sustained RR-interval prolongation that exceeded responses to asynch omissions, sound-present conditions, and rest. HEP amplitude was selectively enhanced in the synch-omission condition relative to all other conditions. Reaction times to the first post-omission tone were slightly delayed, whereas overall performance remained comparable across conditions. These findings show that heartbeat-synchronous auditory omissions produce a distinct autonomic-cortical response profile under active response demands, indicating that heart-brain loop dynamics continue to shape physiological responses during ongoing behaviour.

neuroscience↗

bioRxiv2026

A hierarchical generative model reveals enhanced latent precision of brain-body interaction dynamics during interoceptive attention

Brain-body interactions (BBIs) are fundamental to cognition and mental health, but their continuous multimodal dynamics remain difficult to extract. Previous approaches have been largely observational, and few frameworks enable these interacting processes to be modeled within an integrated generative system. Here, we applied a Predictive-Coding-Inspired Variational RNN (PV-RNN) to simultaneous EEG, ECG, and respiration recordings obtained from 33 participants during exteroceptive and interoceptive attention. The model learned a temporal hierarchy spanning modality-specific dynamics, multimodal associative integration, and sequence-level global states, and accurately reconstructed unseen physiological sequences. Specifically, the intermediate associative layer successfully captured the core complexities of BBI by extracting multiscale, nonlinear, and bidirectional coupling dynamics with variable temporal lags. Furthermore, the estimated precision (inverse variance) of latent variables representing BBI dynamics within this multimodal associative layer increased significantly during interoceptive attention. The magnitude of this condition-dependent precision enhancement correlated positively with subjective adaptive body controllability and negatively with psychiatric vulnerabilities, including rumination and trait anxiety. These findings identify a latent physiological signature of interoceptive attention and establish hierarchical generative modeling as an interpretable framework for extracting continuous BBI dynamics and linking multimodal physiology to cognitive and clinical characteristics.

neuroscience↗

bioRxiv2024

Brain-Body Interactions Influence the Transition from Mind Wandering to Awareness of Ongoing Thought

Our thoughts are inherently dynamic and often wander far from our current situation (mind wandering, MW). Although previous research revealed that the ascending arousal system shapes neural dynamics to mediate awareness of ongoing thoughts, the physiological states and afferent signals altered by this activation and its effects on awareness are unknown. In this study, we examined electroencephalography (EEG), electrocardiography (ECG), and respiration data before participants were aware of MW during a task in which they focused on external or internal stimuli. We showed that the transition from MW to awareness was characterized by decreased alpha and beta activity and increased heartbeat-evoked potential (HEP) amplitudes. In addition, the participants were more likely to be in the exhalation phase becoming aware, and in the inhalation phase at the time of MW reports. Moreover, changes in cardiac activity and HEP accompanied this pattern when participants were asked to focus on respiration. Based on these findings, we suggest that the release from the increased cognitive load with sustained MW and catching these changes as physiological alterations supporting awareness of MW; moreover, the modulation of the respiratory cycle by focusing on breathing enhances these changes.

neuroscience↗

bioRxiv2024

The Body Mirroring Thought: The Relationship Between Thought Transitions and Fluctuations in Autonomic Nervous Activity Mediated by Interoception

Our thought states change unconsciously. This study verified that the transference of thought states varies with fluctuations in autonomic nervous activity, and that this effect is modulated by interoceptive accuracy. The participants completed the heartbeat counting task (HCT) and vigilance task (VT). We assessed the participants interoceptive accuracy based on their performance on the HCT. The VT is a simple attention task, and during this task, we asked the participants to report the content and contemplation of their thoughts. Consequently, participants with accurate interoception were more likely to remain in a highly contemplative thought state when sympathetic activity was activated. In contrast, the dominance of parasympathetic activity facilitated transitions to different thought states or experiences of less contemplative thought states in them. The results suggest that even subtle changes in bodily responses at rest can affect thought transitions in people with accurate interoception.

neuroscience↗

bioRxiv2024

Effects of unconscious tactile stimuli on autonomic nervous activity and afferent signal processing

Autonomic nervous system (ANS) is a mechanism that regulates our internal environment. In recent years, the interest in how tactile stimuli presented directly to the body affect ANS function and cortical processing in humans has been renewed. However, it is not yet clear how subtle tactile stimuli below the level of consciousness affect human heart rate and cortical processing. To examine this, subthreshold electrical stimuli were presented to the left forearm of 43 participants during an image-viewing task, and electrocardiogram (ECG) and electroencephalogram (EEG) data were collected. The changes in the R-wave interval of the ECG immediately after the subthreshold electrical presentation and heartbeat-evoked potential (HEP), the afferent signal processing of cardiac activity, were measured. The results showed that heart rate decelerated immediately after the presentation of subthreshold electrical stimuli. The HEP during stimulus presentation was amplified for participants with greater heart rate acceleration immediately after this deceleration. The magnitude of these effects depended on the type of the subthreshold tactile stimuli. The results suggest that even with subthreshold stimulation, the changes in autonomic activity associated with orienting response and related afferent signal processing differ depending on the clarity of the tactile stimuli.

neuroscience↗

bioRxiv2024

Extending Homeostasis as the Principle of Driving Behavior to the Thought Dynamics Allows Comprehensive Explanation of Mind Wandering

Our thoughts are inherently dynamic, often wandering far from the current situation. Mind-wandering (MW), which is these thought transitions, is crucial for understanding the nature of human thought. Although previous research has identified various factors influencing MW, a comprehensive framework integrating these findings remains absent. Here, we propose that homeostasis has the potential to explain MW and validate the idea through simulations by replicating previous findings. We employed a homeostatic reinforcement learning model where independent drives for the task and others were assigned, and drive reduction became a reward and trained under sustained attention to the response task. We confirmed that the model behaves consistently with the empirical results reported in human experiments, suggesting that the model accurately captures the underlying mechanism of MW. Finally, we discuss the behavioral and neurobiological commonality between human thought and animal behavior and the possibility that the same principle, homeostasis, controls these phenomena.

animal behavior and cognition↗