Addressing the need for new interoceptive methods

Cardiac interoception in the museum: A novel measure of experience

Interoception is the perception of the body's internal signals in response to various external and internal stimuli. The present study uses a novel method adapted from the CARdiac Elevation Detection Task to examine cardiac interoception objectively and subjectively in a unique context-in the presence of art. Self-report questionnaires were used to measure subjective interoceptive awareness, subjective interoceptive accuracy, and aesthetic appreciation. For objective interoceptive accuracy and sensibility, a wearable device (Shimmer) measured heart rate (HR) and connected to a mobile application to prompt two questions: "Is your heart beating faster than usual?" and "How confident are you in your previous response?" Participants explored an art gallery for 40 minutes while the Shimmer measured their HR and randomly prompted them to answer the questions. Using a Generalized Estimating Equation model, interoceptive sensibility was not found to predict the odds of submitting a correct response. It was also found that art does not improve participants' perceptions of their HR. Finally, there was no relation between aesthetic appreciation and subjective or objective cardiac interoception. Despite lack of statistical significance, the current study's method presents an improved method by examining interoceptive accuracy in the moment under ecological conditions. To date, findings and methods used in interoception are inconsistent or flawed; the value in the current study lies in the development and demonstration of a method to examine how the environment influences the body and self-awareness across a wide variety of contexts, thereby offering a possible standardized measure of interoception for investigators to adopt.

The duration discrimination respiratory task: A new test to measure respiratory interoceptive accuracy

Interoception, which refers to the perception of body's internal state, is implicated in emotional processes and psychopathological disorders. Over the last decades, different tools have been developed to measure interoceptive accuracy, or the ability to accurately perceive physiological signals. Most of these tools have focused on cardiac interoception, but respiratory interoception has been less investigated due to the more complex and less portable equipment required. In this study, we suggest a new duration discrimination respiratory (DDR) task that does not require complex equipment. Using an adaptive staircase procedure, this task aims to determine an individual's ability to detect exhalation longer than their resting reference duration. One hundred and twenty-three healthy subjects completed the DDR task, an interoceptive task of heart rate discrimination, and filled out questionnaires on interoceptive awareness (Multidimensional Assessment of Interoceptive Awareness), alexithymia (Toronto Alexithymia Scale [TAS]), affects (Positive and Negative Affect Scale [PANAS]), and anamnestic. Results demonstrated a good internal consistency (Cronbach's alpha = .93) of the DDR task. On average, subjects needed 99.22% (SD = 36.38) of their reference exhalation time in addition to reference exhalation to detect a prolonged exhalation. Higher self-reported fitness levels, not counting during the DDR task and lower difficulty in describing feelings (TAS subscale), predicted higher respiratory discrimination duration. In conclusion, this study demonstrates the utility of the DDR task as a valid measure of interoception.

Perceptual Dysfunction in Eating Disorders

Eating disorders (EDs) are characterized by abnormal responses to food and weight-related stimuli and are associated with significant distress, impairment, and poor outcomes. Because many of the cardinal symptoms of EDs involve disturbances in perception of one's body or abnormal affective or cognitive reactions to food intake and how that affects one's size, there has been longstanding interest in characterizing alterations in sensory perception among differing ED diagnostic groups. Within the current review, we aimed to critically assess the existing research on exteroceptive and interoceptive perception and how sensory perception may influence ED behavior. Overall, existing research is most consistent regarding alterations in taste, visual, tactile, and gastric-specific interoceptive processing in EDs, with emerging work indicating elevated respiratory and cardiovascular sensitivity. However, this work is far from conclusive, with most studies unable to speak to the precise etiology of observed perceptual differences in these domains and disentangle these effects from affective and cognitive processes observed within EDs. Further, existing knowledge regarding perceptual disturbances in EDs is limited by heterogeneity in methodology, lack of multimodal assessment protocols, and inconsistent attention to different ED diagnoses. We propose several new avenues for improving neurobiology-informed research on sensory processing to generate actionable knowledge that can inform the development of innovative interventions for these serious disorders.

The Neurophysiology of Interoceptive Disruptions in Trauma-Exposed Populations

In the aftermath of psychological trauma, many individuals experience perturbations in interoception, a term that broadly references the ability to accurately detect body signals and integrate these signals with emotional states. These interoceptive disruptions can manifest in different ways, including blunting or amplification of sensitivity to internal physiological signals. In this chapter we review extant neurophysiological research on interoception in trauma-exposed populations, with a particular focus on the effects of chronic interpersonal trauma, such as childhood maltreatment and racial discrimination. We explore research that used different types of interoceptive assays, from self-report measures to electrophysiological and neuroimaging tools to characterize the disruptions in pain perception, interoceptive acuity, and physiological responses that may arise after a traumatic event. Finally, we discuss interventions that are designed to target interoceptive mechanisms, from exposure-based therapies to mindfulness-based practices, as well as future directions in trauma interoception research.

A computationally informed distinction of interoception and exteroception

While interoception is of major neuroscientific interest, its precise definition and delineation from exteroception continue to be debated. Here, we propose a functional distinction between interoception and exteroception based on computational concepts of sensor-effector loops. Under this view, the classification of sensory inputs as serving interoception or exteroception depends on the sensor-effector loop they feed into, for the control of either bodily (physiological and biochemical) or environmental states. We explain the utility of this perspective by examining the perception of skin temperature, one of the most challenging cases for distinguishing between interoception and exteroception. Specifically, we propose conceptualising thermoception as inference about the thermal state of the body (including the skin), which is directly coupled to thermoregulatory processes. This functional view emphasises the coupling to regulation (control) as a defining property of perception (inference) and connects the definition of interoception to contemporary computational theories of brain-body interactions.

The relationship between mindfulness and athletes' mental skills may be explained by emotion regulation and self-regulation

BACKGROUND

Although numerous psychological determinants of sports success have been identified in the scientific literature, research on the contribution of mindfulness and interoceptive awareness to sports achievements remains limited. This study investigates the relationship between self-reported mental skills determining sports success (i.e., flow state, attention, technique, sensitivity to error, commitment, and achievement), state mindfulness for physical activity (of the mind and the body), and interoceptive awareness (including scales of noticing, not distracting, not worrying, attention regulation, emotional awareness, self-regulation, body listening, and trusting).

METHODS

A cross-sectional online survey was conducted on a sample of elite athletes in speed skating (n = 54) and university students of physical education (n = 102) representing various sports disciplines and competitive levels. The Sports Success Scale (SSS), the State Mindfulness Scale for Physical Activity (SMS-PA), and the Multidimensional Assessment of Interoceptive Awareness (MAIA-2) were used to assess psychological determinants of athletic achievements, state mindfulness, and interoceptive sensitivity, respectively.

RESULTS

Our findings indicate some small-to-moderate differences in particular dimensions of psychological traits related to sports success, mindfulness, and interoceptive awareness between athletes of different genders, groups, and competitive levels. A chain mediation model showed that the relationship between body mindfulness and psychological variables determining sports success is fully explained by two dimensions of interoception: self-regulation and attention regulation.

CONCLUSIONS

Cultivating the mindfulness state of the body can improve self-regulation and attention regulation, which in turn may increase the mental skills required for successful sports participation. Therefore, mental training should focus primarily on body mindfulness, attention regulation, and self-regulation to improve the mental skills responsible for athletes' sports achievements. In addition, individual differences in athletes' gender, sports discipline, and level of sports competition should be considered during mental training.

Thermosensation and emotion: Thermosensory accuracy in a dynamic thermal matching task is linked to depression and anxiety symptomatology

Interoception is related to the generation of bodily feelings and the awareness of ourselves as 'sentient beings', informing the organism about its bodily needs to guarantee survival. Previous studies have reported links among interoception, emotion processing, and mental health. For example, the alignment of interoceptive dimensions (i.e., accuracy, sensibility, awareness) can predict emotional symptoms, such as anxiety. Here, we aimed to investigate the relationship between the perception of a certain type of skin-mediated interoceptive signal, i.e., thermosensation, and self-reported depression, anxiety, and stress. One hundred seventy participants completed the Depression Anxiety Stress Scale (DASS-21) and a dynamic thermal matching task, a static temperature detection task, and a heartbeat counting task. Our results revealed that self-reported anxiety and depression were related to the perception of temperature on hairy and non-hairy skin, respectively: higher anxiety was related to better performance on the thermal matching task on the forearm, while higher depression was related to poorer performance on dynamic and static temperature tasks on the palm. Discrepancies between thermosensory accuracy and sensibility measures ('trait prediction error') were related to heightened anxiety, in line with previous studies. No significant correlations were found between DASS-21 scores and heartbeat counting accuracy. In conclusion, this study suggests that individual differences in thermosensory perception in different areas of the body are associated with self-reported anxiety and depression.

Pain and related suffering reduce attention toward others

BACKGROUND

It has been proposed that the expression of pain-related suffering may lead to an enhanced focus on oneself and reduced attention toward the external world. This study aimed at investigating whether experimentally induced painrelated suffering may lead persons to withdraw into themselves, causing a reduced focus on external stimuli as reflected by impaired performance in a facial recognition task and heightened perception of internal stimuli measured by interoceptive awareness.

METHODS

Thirty-two participants had to recognize different emotional facial expressions (neutral, sad, angry, happy), or neutral geometrical figures under conditions of no pain, low, and high prolonged pain intensities. Interoceptive accuracy was measured using a heartbeat-detection task prior to and following the pain protocol.

RESULTS

Males but not females were slower to recognize facial expressions under the condition of high painful stimulation compared to the condition of no pain. In both, male and female participants, the difficulty in recognizing another person's emotions from a facial expression was directly related to the level of suffering and unpleasantness experienced during pain. Interoceptive accuracy was higher after the pain experiment. However, neither the initial interoceptive accuracy nor the change were significantly related to the pain ratings.

CONCLUSIONS

Our results suggest that long-lasting and intense painful stimuli, which induce suffering, lead to attentional shifts leading to withdrawal from others. These findings contribute to a better understanding of the social dynamics of pain and pain-related suffering.

Interoceptive awareness in a Norwegian population: psychometric properties of the Multidimensional Assessment of Interoceptive Awareness (MAIA) 2

BACKGROUND

Interoception plays a vital role in human cognition and emotion and is an increasingly important part of clinical studies of mind-body approaches and mental health. Interoceptive awareness (IA) encompasses numerous mind-body components and can be assessed by employing a self-report measure such as the Multidimensional Assessment of Interoceptive Awareness (MAIA), which has been adapted and validated across several countries and is used in experimental and clinical settings. In this study, the MAIA-2, which was developed due to the psychometric shortages of MAIA, was thoroughly translated, and its psychometric features were examined in a sample of 306 Norwegian-speaking participants (81% females, ages 16 through 66 plus).

METHODS

The participants completed the MAIA-2 Norwegian version (MAIA-2-N) and the COOP/WONCA Functional Assessment Charts measuring psychological, physical, and overall health. The following psychometric qualities of the MAIA-2 were investigated: factor structure, internal consistency, and the moderating role of gender.

RESULTS

Confirmatory Factor Analysis (CFA) revealed that an 8-factor model of MAIA-2-N provided the best fit. Also, a bifactor model revealed a proper fit. Good internal consistency and a moderating role of gender, age, and education on the relationships between certain MAIA-2-N factors and health were observed.

CONCLUSIONS

The MAIA-2-N is an adequate measure of IA in Norwegian-speaking individuals. The factor-structure corresponds with the original MAIA-2 and it shows good internal consistency. Some moderating effects of gender were observed, particularly related to the relationship between IA and physical and psychological state, with the physical state/fitness more closely linked to IA in males and psychological state in females.

Multidimensional assessment of anticipated and experienced interoceptive states

As the sense of the body's internal state, interoception represents the afferent component of the brain-body feedback loop essential for linking internal sensation with body regulation, thereby minimizing erroneous feedback and maintaining homeostasis. The anticipation of potential future interoceptive states enables organisms to take regulatory actions to meet demands before they arise, and alterations of anticipation have been implicated in the pathophysiology of medical and psychiatric conditions. However, laboratory approaches operationalizing the anticipation of interoceptive states are missing. Therefore, we developed two interoceptive awareness paradigms, the Accuracy of Interoceptive Anticipation paradigm, and the Interoceptive Discrepancy paradigm, which we tested in 52 healthy participants on two sensory modalities: nociception and respiroception. Ten participants took part in a retest. The Accuracy of Interoceptive Anticipation paradigm focused on assessing how individuals anticipate and experience interoceptive stimuli of varying strengths. The Interoceptive Discrepancy paradigm extended this measure by manipulating previously learned expectations to induce discrepancies between anticipated and experienced stimuli. We found that anticipation and experience ratings successfully related to stimulus strength in both paradigms and modalities and were stable between test-retest. Furthermore, the Interoceptive Discrepancy paradigm successfully induced the expected discrepancies between anticipation and experience conditions, and discrepancy values were correlated across sensory modalities. Thus, both paradigms are valid and reliable tools for assessing the anticipation of future interoceptive states, and the Interoceptive Discrepancy paradigm is additionally suited to evaluate discrepancy awareness.

Interoceptive accuracy correlates with precision of time perception in the millisecond range

It has been proposed that accuracy in time perception is related to interoceptive accuracy and vagal activity. However, studies investigating time perception in the supra-second range have provided mixed results, and few studies have investigated the sub-second range. Moreover, there is a lack of studies investigating the relationship between precision in time perception and interoceptive accuracy. A recent meta-analytic review of neuroimaging studies proposed a dynamic interaction between two types of timing processing-an endogenous time keeping mechanism and the use of exogenous temporal cues. Interoceptive accuracy may affect both accuracy and precision of primary temporal representations, as they are generated based on the endogenous time keeping mechanism. Temporal accuracy may vary when adapted to the environmental context. In contrast, temporal precision contains some constant noise, which may maintain the relationship with interoceptive accuracy. Based on these assumptions, we hypothesized that interoceptive accuracy would be associated with temporal precision in the sub-second range, while vagal activity would be associated with temporal accuracy. We used the temporal generalization task, which allowed us to calculate the indices of temporal accuracy and temporal precision in line with the existing research, and also compute the index of participants' sensitivity according to the signal detection theory. Specifically, we investigated whether (1) interoceptive accuracy would correlate with temporal accuracy, temporal precision, or sensitivity and (2) resting-state vagal activity would correlate with temporal accuracy, temporal precision, or sensitivity. The results indicated that interoceptive accuracy was positively correlated with temporal precision as well as sensitivity, but not with temporal accuracy, in the sub-second range time perception. Vagal activity was negatively correlated only with sensitivity. Furthermore, we found a moderation effect of sensitivity on the relationship between vagal activity and perceived duration, which affected the association between vagal activity and temporal accuracy. These findings suggest the importance of precision as an aspect of time perception, which future studies should further explore in relation to interoception and vagal activity, and of the moderation effects of factors such as participants' sensitivity in this context.

Acute physical-activity related increases in interoceptive ability are not enhanced with simultaneous interoceptive attention

Interoception, the sense of the internal body, is proposed to support self-regulation, and consequently influence mental health. Researchers have therefore shown interest in improving the ability to accurately monitor internal signals (i.e., interoceptive accuracy, IAcc). Research suggests that cardiac IAcc is modifiable by both manipulations of interoceptive attention (guided attention towards the internal body), and interoceptive exposure (strategically inducing somatic signals e.g., via physical activity). Whilst successful in isolation, it is unclear whether a combined approach (i.e., directing attention towards the internal body when signals are more salient) could elicit greater benefits. In a 2 × 2 within-subject design, 48 healthy adults (M_age = 25.98 ± 4.73 years, 50% female) completed four 20-min conditions varying in both attentional focus (interoceptive vs exteroceptive) and physical activity (active vs rest), with cardiac IAcc measured immediately after. Results revealed a main effect for physical activity (p < 0.001), however, there was no effect for attentional focus (p = 0.397), and no interaction effect (p = 0.797). Differential analyses showed that a higher sporting background increased sensitivity to physical activity-related increases in cardiac IAcc (p = 0.031). Findings indicate that (irrespective of attentional focus) moderate-vigorous physical activity-based interventions have the potential to increase cardiac IAcc, with certain individuals potentially benefiting more.

Brain-heart interactions are modulated across the respiratory cycle via interoceptive attention

Respiration and heartbeat continuously interact within the living organism at many different levels, representing two of the main oscillatory rhythms of the body and providing major sources of interoceptive information to the brain. Despite the modulatory effect of respiration on exteroception and cognition has been recently established in humans, its role in shaping interoceptive perception has been scarcely investigated so far. In two independent studies, we investigated the effect of spontaneous breathing on cardiac interoception by assessing the Heartbeat Evoked Potential (HEP) in healthy humans. In Study 1, we compared HEP activity for heartbeats occurred during inhalation and exhalation in 40 volunteers at rest. We found higher HEP amplitude during exhalation, compared to inhalation, over fronto-centro-parietal areas. This suggests increased brain-heart interactions and improved cortical processing of the heartbeats during exhalation. Further analyses revealed that this effect was moderated by heart rate changes. In Study 2, we tested the respiratory phase-dependent modulation of HEP activity in 20 volunteers during Exteroceptive and Interoceptive conditions of the Heartbeat Detection (HBD) task. In these conditions, participants were requested to tap at each heartbeat, either listened to or felt, respectively. Results showed higher HEP activity and higher detection accuracy at exhalation than inhalation in the Interoceptive condition only. Direct comparisons of Interoceptive and Exteroceptive conditions confirmed stronger respiratory phase-dependent modulation of HEP and accuracy when attention was directed towards the interoceptive stimuli. Moreover, HEP changes during the Interoceptive condition were independent of heart physiology, but were positively correlated with higher detection accuracy at exhalation than inhalation. This suggests a link between optimization of cortical processing of cardiac signals and detection of heartbeats across the respiratory cycle. Overall, we provide data showing that respiration shapes cardiac interoception at the neurophysiological and behavioural levels. Specifically, exhalation may allow attentional shift towards the internal bodily states.