Neural correlates of interoceptive accuracy: Beyond cardioception

Alexithymia shapes intersubject synchrony in brain activity during interoceptive sensation representations

Alexithymia is a subclinical condition that affects individuals' processing of emotions. Emerging evidence suggests that alexithymia results from a multidomain and multidimensional interoceptive failure. Although extensive research has examined the relationship between alexithymia and interoception, less is known about how alexithymia modulates the brain activity evoked by interoceptive sensations. In this study, we used task-based functional magnetic resonance imaging (fMRI) to assess intersubject correlations in response to interoceptive sensation words in individuals with high alexithymia and low alexithymia. Participants with high alexithymia (n = 29) and low alexithymia (n = 28) were instructed to view words during MRI scanning, each word corresponding to a specific emotional category related to interoceptive sensations. Intersubject correlation analysis identified several brain regions exhibiting increased synchronization in individuals with high alexithymia, including those involved in cognitive control. Follow-up analyses revealed that the left middle occipital gyrus and the right inferior frontal gyrus (orbital part) were more active during interoceptive sensation events in individuals with high alexithymia. Validation analyses revealed that the amygdala and insula are also crucial in representing interoceptive sensations. These findings shed light on the neural basis of interoceptive deficits in high alexithymia and have significant implications for the mechanisms regulating these differences.

The anterior cingulate cortex is involved in intero-exteroceptive integration for spatial image transformation of the self-body

Spatial image transformation of the self-body is a fundamental function of visual perspective-taking. Recent research underscores the significance of intero-exteroceptive information integration to construct representations of our embodied self. This raises the intriguing hypothesis that interoceptive processing might be involved in the spatial image transformation of the self-body. To test this hypothesis, the present study used functional magnetic resonance imaging to measure brain activity during an arm laterality judgment (ALJ) task. In this task, participants were tasked with discerning whether the outstretched arm of a human figure, viewed from the front or back, was the right or left hand. The reaction times for the ALJ task proved longer when the stimulus presented orientations of 0°, 90°, and 270° relative to the upright orientation, and when the front view was presented rather than the back view. Reflecting the increased reaction time, increased brain activity was manifested in a cluster centered on the dorsal anterior cingulate cortex (ACC), suggesting that the activation reflects the involvement of an embodied simulation in ALJ. Furthermore, this cluster of brain activity exhibited overlap with regions where the difference in activation between the front and back views positively correlated with the participants' interoceptive sensitivity, as assessed through the heartbeat discrimination task, within the pregenual ACC. These results suggest that the ACC plays an important role in integrating intero-exteroceptive cues to spatially transform the image of our self-body.

Revisiting uncertainty as a felt sense of unsafety: The somatic error theory of intolerance of uncertainty

Intolerance of uncertainty (IU) has gained widespread interest as a construct of broad interest from both transdiagnostic and trans-situational perspectives. We have approached this article inspired by the curiosity, clinical observation, consideration of different theoretical perspectives, speculation, optimism and indeed fun that can be seen in S. J. Rachman's work. We address some of what we know about IU before considering one way of conceptualizing IU from the standpoint of a felt sense or embodied experience. In the first part, we start with Woody and Rachman's (1994) observations of people with GAD. Second, we consider some key findings from the literature. Third, we consider two important perspectives on uncertainty, namely, Brosschot et al.'s (2016, 2018) influential Generalized Unsafety Theory of Stress and uncertainty as an emotion. In the second part, backing our clinical hunch about the importance of the felt sense of uncertainty, we consider IU from the perspective of interoception and the somatic error theory of anxiety (Khalsa & Feinstein, 2018). We propose the somatic error theory of intolerance of uncertainty, which places the experience of uncertainty at the heart of our understanding of intolerance of uncertainty. This is followed by predictions, unresolved questions, and potential clinical implications. Finally, we revisit Woody and Rachman's (1994) suggestions for treatment as internalizing "a sense of safety in a range of circumstances (p. 750)" and update this from the perspective of the felt sense of uncertainty. We finish by suggesting that uncertainty can be tolerated, perhaps accepted, and even embraced.

Interoceptive Awareness of the Breath Preserves Attention and Language Networks amidst Widespread Cortical Deactivation: A Within-Participant Neuroimaging Study

Interoception, the representation of the body's internal state, serves as a foundation for emotion, motivation, and wellbeing. Yet despite its centrality in human experience, the neural mechanisms of interoceptive attention are poorly understood. The Interoceptive/Exteroceptive Attention Task (IEAT) is a novel neuroimaging paradigm that compares behavioral tracking of the respiratory cycle (Active Interoception) to tracking of a visual stimulus (Active Exteroception). Twenty-two healthy participants completed the IEAT during two separate scanning sessions (N = 44) as part of a randomized control trial of mindful awareness in body-oriented therapy (MABT). Compared with Active Exteroception, Active Interoception deactivated somatomotor and prefrontal regions. Greater self-reported interoceptive sensibility (MAIA scale) predicted sparing from deactivation within the anterior cingulate cortex (ACC) and left-lateralized language regions. The right insula, typically described as a primary interoceptive cortex, was only specifically implicated by its deactivation during an exogenously paced respiration condition (Active Matching) relative to self-paced Active Interoception. Psychophysiological interaction (PPI) analysis characterized Active Interoception as promoting greater ACC connectivity with lateral prefrontal and parietal regions commonly referred to as the dorsal attention network (DAN). In contrast to evidence relating accurate detection of liminal interoceptive signals such as the heartbeat to anterior insula activity, interoceptive attention toward salient signals such as the respiratory cycle may involve reduced cortical activity but greater ACC-DAN connectivity, with greater sensibility linked to reduced deactivation within the ACC and language-processing regions.

Cardiac and Gastric Interoceptive Awareness Have Distinct Neural Substrates

Interoceptive awareness, an awareness of the internal body state, guides adaptive behavior by providing ongoing information on body signals, such as heart rate and energy status. However, it is still unclear how interoceptive awareness of different body organs are represented in the human brain. Hence, we directly compared the neural activations accompanying attention to cardiac (related to heartbeat) and gastric (related to stomach) sensations, which generate cardiac and gastric interoceptive awareness, in the same population (healthy humans, N = 31). Participants were asked to direct their attention toward heart and stomach sensations and become aware of them in a magnetic resonance imaging (MRI) scanner. The results indicated that the neural activations underlying gastric attention encompassed larger brain regions, including the occipitotemporal visual cortices, bilateral primary motor cortices, primary somatosensory cortex, left orbitofrontal cortex, and hippocampal regions. Cardiac attention, however, selectively activated the right anterior insula extending to the frontal operculum compared with gastric attention. Moreover, our detailed analyses focusing on the insula, the most relevant region for interoceptive awareness, revealed that the left dorsal middle insula encoded cardiac and gastric attention via different activation patterns, but the posterior insula did not. Our results demonstrate that cardiac and gastric attention evoke different brain activation patterns; in particular, the selective activation may reflect differences in the functional roles of cardiac and gastric interoceptive awareness.