Physical Exercise to Redynamize Interoception in Substance use Disorders.

Physical exercise is considered a promising medication-free and cost-effective adjunct treatment for substance use disorders (SUD). Nevertheless, evidence regarding the effectiveness of these interventions is currently limited, thereby signaling the need to better understand the mechanisms underlying their impact on SUD, in order to reframe and optimize them. Here we advance that physical exercise could be re-conceptualized as an "interoception booster", namely as a way to help people with SUD to better decode and interpret bodily-related signals associated with transient states of homeostatic imbalances that usually trigger consumption. We first discuss how mismatches between current and desired bodily states influence the formation of reward-seeking states in SUD, in light of the insular cortex brain networks. Next, we detail effort perception during physical exercise and discuss how it can be used as a relevant framework for re-dynamizing interoception in SUD. We conclude by providing perspectives and methodological considerations for applying the proposed approach to mixed-design neurocognitive research on SUD.

The new measures of interoceptive accuracy: A systematic review and assessment.

Conscious interoception, the perception of internal bodily states, is thought to contribute to fundamental human abilities (e.g., decision-making and emotional regulation). One of its most studied dimensions is interoceptive accuracy: the objective capacity to detect internal bodily signals. In the past few years, several labs across the world have started developing new tasks aimed at overcoming limitations inherent in classical measures of interoceptive accuracy. In this systematic review, we identified these tasks (since 2015) for the cardiac, respiratory, and gastrointestinal domains. For each identified task, we discuss their strengths and weaknesses, and make constructive suggestions for further improvement. In the general discussion, we discuss the (potentially elusive) possibility of reaching high validity in the measurement of interoceptive accuracy. We also point out that interoceptive accuracy may not be the most critical dimension for informing current theories, and we encourage researchers to investigate other dimensions of conscious interoception.

Discrepancies in the Definition and Measurement of Human Interoception: A Comprehensive Discussion and Suggested Ways Forward.

Interoception has been the subject of renewed interest over the past 2 decades. The involvement of interoception in a variety of fundamental human abilities (e.g., decision-making and emotional regulation) has led to the hypothesis that interoception is a central transdiagnostic process that causes and maintains mental disorders and physical diseases. However, interoception has been inconsistently defined and conceptualized. In the first part of this article, we argue that the widespread practice of defining interoception as the processing of signals originating from within the body and limiting it to specific physiological pathways (lamina I spinothalamic afferents) is problematic. This is because, in humans, the processing of internal states is underpinned by other physiological pathways generally assigned to the somatosensory system. In the second part, we explain that the consensual dimensions of interoception are empirically detached from existing measures, the latter of which capture loosely related phenomena. This is detrimental to the replicability of findings across measures and the validity of interpretations. In the general discussion, we discuss the main insights of the current analysis and suggest a more refined way to define interoception in humans and conceptualize its underlying dimensions.

Mindfulness-Based Interventions and Body Awareness.

Body awareness (BA) has long been proposed as a working mechanism of mindfulness-based interventions (MBIs), yet research on the mediating role of BA is scarce. Hence, the present study assesses the impact of an 8-week MBI on self-reported and indirect measures of BA, investigates the potential mediating role of BA in the relationship between an MBI and symptomatology, evaluates the impact of an MBI on important psychological processes (i.e., experiential avoidance, rumination, self-efficacy, and self-discrepancy), and explores whether these variables act alongside BA in mediating the relationship between an MBI and symptomatology. A non-randomized controlled trial was conducted with 148 participants (n = 89 in the MBI group; n = 59 in the control group) who completed questionnaires assessing BA and the above-mentioned psychological processes before and after an MBI. A sub-sample of participants (n = 86) completed a task that evaluates BA indirectly. Results showed a significant effect of MBI on the self-reported BA but not on the indirect measure of BA. The MBI significantly reduced symptomatology, and this effect was mediated by regulatory and belief-related dimensions of BA. Multiple mediator models showed a significant mediation via various pathways involving improved BA and various transdiagnostic psychological processes.

What do measures of self-report interoception measure? Insights from a systematic review, latent factor analysis, and network approach.

Recent conceptualizations of interoception suggest several facets to this construct, including "interoceptive sensibility" and "self-report interoceptive scales", both of which are assessed with questionnaires. Although these conceptual efforts have helped move the field forward, uncertainty remains regarding whether current measures converge on their measurement of a common construct. To address this question, we first identified -via a systematic review- the most cited questionnaires of interoceptive sensibility. Then, we examined their correlations, their overall factorial structure, and their network structure in a large community sample (n = 1003). The results indicate that these questionnaires tap onto distinct constructs, with low overall convergence and interrelationships between questionnaire items. This observation mitigates the interpretation and replicability of findings in self-report interoception research. We call for a better match between constructs and measures.

The impact of transcranial Direct Current stimulation on rumination: A systematic review of the sham-controlled studies in healthy and clinical samples.

INTRODUCTION: Broadly considered a transdiagnostic feature of psychological disorders, rumination is associated with lower treatment response, slower recovery rates, and higher relapse rates. Accordingly, research has focused on the development of interventions to alleviate rumination. Recently, transcranial Direct Current Stimulation (tDCS) has emerged as a promising tool to do so. METHODS: We performed a systematic review of sham-controlled tDCS studies targeting rumination among healthy participants or patients with psychiatric disorders, investigating the effectiveness of tDCS in reducing rumination, and assessing the research quality of this nascent field. RESULTS: We identified nine studies, with five reporting a significant impact of tDCS on rumination. We also outlined a few tDCS parameters (e.g., stimulation duration, electrode size) and research methods' features (e.g., within- versus between-research designs) characterizing those positive-finding studies. However, these studies were characterized by substantial heterogeneity (e.g., methodological flaws, lack of open science practices), precluding any definite statement about the best way to target rumination via tDCS. Moreover, several strong methodological limitations were also present across those studies. DISCUSSION: Although our systematic review identifies the strengths and weaknesses of the available research about the impact of tDCS on rumination, it calls for strong efforts to improve this nascent field's current methodological caveats. We discuss how open science practices can help to usher this field forward.

Contribution of Time Estimation and Knowledge to Heartbeat Counting Task Performance under Original and Adapted Instructions.

Interoceptive accuracy is frequently assessed using the Heartbeat Counting Task (HCT), requiring participants to count the number of times their heart beats. The HCT validity has been questioned, as participants may perform the task by estimating, rather than counting, their felt heartbeats. Participants could estimate the time or use their knowledge of their heart rate. Some research ruled out the contribution of time estimation in HCT performance. However, we believe these studies relied on a problematic analytic rationale. We revisited this question by relying on new analytic strategies, and by examining the role of estimation in HCT performance, while varying task instructions. The findings support the role of time and knowledge-based estimations under original instructions. They also highlight the critical impact of instructions on HCT validity. Given the many limitations of the HCT, we urge researchers to test the robustness of published effects and to reconsider the interpretation of replicable results.

A heartfelt response to Zimprich et al. (2020), and Ainley et al. (2020)'s commentaries: Acknowledging issues with the HCT would benefit interoception research.

In two Commentaries, Zimprich et al. (2020), and Ainley et al. (2020) dispute conclusions raised by Zamariola et al. (2018) in a large sample study that questioned the validity of IAcc scores derived from the Heartbeat Counting Task (HCT). After clarifying the reliability of our procedures and the robustness of our main findings, we address the four points of contention discussed in the Commentaries. In doing so, we spell out why research using the HCT faces important interpretational issues, and we call for a theoretical clarification on the construct. In our conclusion, we provide recommendations for improving HCT research and research on interoception in general.

Effects of prebiotics on affect and cognition in human intervention studies.

Studies conducted in rodents have highlighted that neurobiological processes underlying cognition and affect are modulated by the gut microbiota. Certain dietary fibers are able to modulate the composition of gut microbiota and are thus considered prebiotics. A review of the impact of the available prebiotic intervention studies in humans on cognition and affect, addressing the potential mediating role of the microbiota, was conducted. PubMed, Scopus, and PsycINFO were selected as sources. Fourteen articles were eligible for narrative synthesis. Data extraction and quality assessment were performed with characteristics established a priori. Some chronic prebiotic interventions (>28 d) improved affect and verbal episodic memory compared with a placebo. Acute prebiotic interventions (<24 h) were more efficient in improving cognitive variables (eg, verbal episodic memory). Future research should measure microbiota using adequate methodologies and recruit patients with dysbiosis, inflammation, or psychopathology. More research is needed to unravel the conditions required to obtain effects on affect and cognition.

The heartbeat counting task largely involves non-interoceptive processes: Evidence from both the original and an adapted counting task.

The heartbeat counting task (HCT) is among the most frequently used measures of interoceptive accuracy (i.e., IAcc). Growing concerns, however, have been raised regarding the validity of this task, as well as the validity of the IAcc scores that are derived from it. In the present study, healthy participants (N = 123) performed both the original task and an adapted version of it that stressed the importance of reporting only their perceptually felt heartbeats. In the original task, we found that participants report relying on three different strategies (i.e., detection of heartbeats in a specific body location, detection of heartbeats in a diffuse way and heart rate estimation) to complete the task. In the adapted task, we found that IAcc scores are drastically reduced (about 50%) when asking participants to avoid relying on non-interoceptive signals and to only report the heartbeats they perceive. These findings confirm that the HCT task is largely contaminated by the influence of non-interoceptive processes. Implications of these findings for research on interoception are discussed.