Changes in interoception after alcohol administration correlate with expectancies and subjective effects

Validity Concerns About the Heartbeat Counting Task Extend to Alcohol Use disorder: Evidence From Subclinical and Clinical Samples

Theoretical models propose that interoception plays a role in addictive disorder. However, this assumption has been mostly tested using the heartbeat counting task (HCT), which is known to be contaminated by estimation strategies. An adapted version of the HCT (in which respondents report only felt heartbeats) has been developed to reduce estimation biases. Here, we examined the validity of the classical and adapted HCT versions in samples presenting alcohol use disorders. We recruited a clinical sample of 48 patients with severe alcohol use disorder (SAUD), matched with 41 healthy controls (HC), and a subclinical sample of 32 binge drinkers (BD), matched with 30 HC. Participants performed the classical HCT, adapted HCT, and a time estimation task. We additionally assessed mental health variables theoretically related to interoception (alexithymia, anxiety, childhood trauma, depression and emotion regulation). In all groups, HCT scores were smaller in adapted than classical HCT. Patients with SAUD, but not BD, showed lower HCT scores than matched controls, independently of the task. We found no correlation between HCT scores and psychological constructs. Heartbeats reported during classical HCT correlated with seconds reported during time estimation task for SAUD and matched HC, suggesting the use of time estimation strategies to perform the task. The largely reduced HCT performance in the adapted version, the association between HCT performance and time estimation performance and the lack of theoretically expected associations between HCT scores and psychological variables extend doubts on the validity of these tasks for measuring interoceptive accuracy in problematic alcohol consumption.

The role of interoception in lifestyle factors: A systematic review

BACKGROUND

Interoception, the perception of the internal state of the body, offers an underrepresented and intriguing potential avenue for altering lifestyle-related behaviors. Interoception is intrinsically related to maintaining homeostasis and the flexible allostatic regulation of complex demands. Internal bodily states may also be influenced by lifestyle factors and related problems. This systematic review aimed to provide insight into the current state of evidence about the role of interoception in lifestyle factors.

METHODS

Studies from three databases (PubMed, Embase, and Web of Science) were screened for eligibility based on two inclusion criteria: 1) at least one measure of interoception (e.g., interoceptive accuracy, attention, or awareness), and 2) at least one measure of a lifestyle factor (i.e., alcohol consumption, cognitive leisure and relaxation activities, eating behavior, exercise, sleep, or smoking). Risk of bias was assessed using an adjusted quality score checklist, consisting of five items related to study design, population size, exposure measurement, outcome measurement, and adjustment for confounders.

RESULTS

The review included 73 studies. Out of the included studies, 51 measured interoceptive accuracy and 36 measured interoceptive attention. Six studies quantified interoceptive awareness. In terms of lifestyle factors, 26 studies on cognitive leisure and relaxation activities, 19 studies on eating behavior, 12 studies focused on alcohol consumption, 10 studies on exercise, five studies on smoking, and four studies on sleep were identified. Findings show positive relations between interoceptive domains and cognitive leisure and relaxation activities, eating behavior, and exercise. Conversely, the consumption of alcohol is negatively related to interoceptive domains. Studies in the smoking and sleep lifestyle factors were sparse and of varying methodological quality.

DISCUSSION

The findings of this review show that interoceptive domains are associated with various lifestyle factors, but the quality of the evidence is limited. Future longitudinal studies with more objective measures of interoception are needed in order to better understand the interrelations between interoception and lifestyle factors.

WACARDIA: Graphical MATLAB software for Wireless Assessment of CARDiac Interoceptive Accuracy

Many theories of psychological function emphasize the importance of bodily sensations and the ability to accurately detect them, known as interoceptive accuracy. The most common measure of interoceptive accuracy uses heartbeat detection tasks such as the Whitehead Task, yet to our knowledge there are no freely accessible programs to conduct this task. In this paper, we present novel software called WACARDIA (Wireless Assessment of CARDiac Interoceptive Accuracy), which is free, open-source software that conducts the heartbeat detection task using Matlab and Psychtoolbox. WACARDIA contains several key features supporting participant engagement, operator convenience, and measurement accuracy. First, the program includes an optional practice trial of unlimited duration, a participant-facing graphical interface, and the ability to perform heartbeat detection training. Second, the operator is provided with a graphical user interface, live trial feedback, an accurate wireless electrocardiogram device, and a separate program to conduct the related Heartbeat Tracking task. Finally, the program ensures the accuracy of collected data by scheduling the delivery of tones with high precision and implementing fail-safes to automatically reset erroneous measurements. This paper includes flowcharts that help create transparency by describing our algorithm. We also outline customizable aspects of the program with the intent to have WACARDIA's algorithm expanded to accommodate more situations and applications. With this paper, we hope to encourage the practice of publicizing research software to contribute to the transparency, rigor, and reproducibility of scientific studies. WACARDIA and video tutorials are available at www.github.com/iankleckner/wacardia and http://wacardia.iankleckner.com.

Characterizing alcohol cue reactive and non-reactive individuals with alcohol use disorder

PURPOSE

Exposure to alcohol-related cues is thought to elicit a conditional response characterized by increased craving in individuals with alcohol use disorder (AUD). In the context of AUD research, it is important to consider that not all individuals with an AUD are alcohol cue reactive. This study systematically examined subjective alcohol cue reactivity and its clinical and drinking correlates in individuals with an AUD enrolled in a human laboratory pharmacotherapy trial.

METHODS

Individuals with current moderate-to-severe AUD (N = 52) completed a standard alcohol cue exposure paradigm and individual difference assessments as part of a human laboratory pharmacotherapy trial (NCT04249882). We classified participants as cue reactive (CR+) and cue non-reactive (CR-), as indicated by self-reported, subjective alcohol urge, and examined group differences in baseline clinical characteristics and drinking outcomes over the course of the trial.

RESULTS

Twenty participants (38%) were identified as CR+, while 32 participants (62%) were identified as CR-. The CR+ and CR- groups did not differ in baseline drinking and AUD clinical characteristics, but the groups differed in race composition (p = 0.02) and smoking prevalence (p = 0.04) such that the CR+ group had lower prevalence of smokers. The CR+, compared with the CR-, group drank more during the trial titration period (p = 0.03). Both groups reduced drinking across the trial (p's < 0.001), but the CR+ group exhibited a smaller reduction in drinking, compared with the CR- group (time x group, p = 0.029; CR-, p < 0.0001; CR+: p = 0.01).

CONCLUSION

Results indicate that cue reactivity is a heterogenous construct. Recognizing this heterogeneity, and the clinical factors associated with it, is critical to advancing this paradigm as an early efficacy marker in AUD research.

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.

Substitution therapy for patients with alcohol dependence: Mechanisms of action and efficacy

New approaches for the treatment of alcohol dependence (AD) may improve patient outcomes. Substitution maintenance therapy is one of the most effective treatment options for opioid and nicotine use disorders. So far, there has been little attention to substitution therapy for the treatment of AD. Here, we explain the mechanistic foundations of alcohol substitution maintenance therapy. Alcohol has many primary targets in the brain (and other organs) and the physical interaction of ethanol molecules with these specific ethanol-sensitive sites on a variety of ionotropic receptors (e.g. GABA-A, NMDA, and nicotinic acetylcholine (nACh) receptors) and ion channels provides the rationale for substitution. As such, a variety of compounds can interact with those ethanol-sensitive sites and can thus substitute for some of the effects of alcohol. For some of these compounds, alcohol discrimination studies have shown their substitution potential. Accordingly, potential substitution treatments include agonists acting at GABA receptors such as sodium oxybate, baclofen and benzodiazepines, NMDA receptor antagonists such as ketamine and memantine, or nAChRs agonists such as varenicline. All these compounds are already approved for other indications and we present clinical evidence for these drugs in the treatment of alcohol withdrawal syndrome (AWS) and in the long-term treatment of AD, and outline future steps for their acceptance as substitution treatment in AD. Finally, we discuss the substitution approach of managed alcohol programs for the most severely affected homeless populations. Results showed that sodium oxybate is probably the closest to a substitution therapy for AD and is already approved for the treatment of AWS and in the long-term treatment of AD in some countries. In conclusion, we argue that better AD treatment can be provided if substitution maintenance treatments for alcohol are implemented at a similar scale as for opioid and nicotine use disorder.

Interoception and alcohol: Mechanisms, networks, and implications

Interoception refers to the perception of the internal state of the body and is increasingly being recognized as an important factor in mental health disorders. Drugs of abuse produce powerful interoceptive states that are upstream of behaviors that drive and influence drug intake, and addiction pathology is impacted by interoceptive processes. The goal of the present review is to discuss interoceptive processes related to alcohol. We will cover physiological responses to alcohol, how interoceptive states can impact drinking, and the recruitment of brain networks as informed by clinical research. We also review the molecular and brain circuitry mechanisms of alcohol interoceptive effects as informed by preclinical studies. Finally, we will discuss emerging treatments with consideration of interoception processes. As our understanding of the role of interoception in drug and alcohol use grows, we suggest that the convergence of information provided by clinical and preclinical studies will be increasingly important. Given the complexity of interoceptive processing and the multitude of brain regions involved, an overarching network-based framework can provide context for how focused manipulations modulate interoceptive processing as a whole. In turn, preclinical studies can systematically determine the roles of individual nodes and their molecular underpinnings in a given network, potentially suggesting new therapeutic targets and directions. As interoceptive processing drives and influences motivation, emotion, and subsequent behavior, consideration of interoception is important for our understanding of processes that drive ongoing drinking and relapse.

Cardiovascular mechanisms of interoceptive awareness: Effects of resonance breathing

Interoception, the ability to perceive internal bodily sensations, and heart rate variability (HRV) share common physiological pathways, including the baroreflex feedback loop. The baroreflex can be activated by resonance breathing, wherein respiration is paced at 6 times per minute (0.1 Hz), eliciting immediate physiological changes and longer-term therapeutic responses. This registered report characterizes baroreflex functioning as a cardiac mechanism of interoception in a two-session study (n = 67). The heartbeat discrimination task was used to obtain indices of interoceptive accuracy, sensibility and metacognition. Baroreflex functioning was measured as HRV at 0.1 Hz and baroreflex sensitivity (BRS); high frequency (HF) HRV was calculated as a control. Cardiovascular indices were measured at baseline and during active and control paced breathing after which changes in interoception were measured. The first hypothesis was that baseline baroreflex functioning would predict individual differences in interoceptive awareness. The second hypothesis was that resonance breathing would increase participants' ability to detect their own heartbeats, and that this effect would be mediated by increases in 0.1 Hz HRV and BRS. Data were collected upon in principle acceptance of the manuscript. We found a negative relationship of interoceptive accuracy with baseline HF HRV and BRS, and a positive relationship between metacognitive interoception and 0.1HZ HRV, BRS and HF HRV. We found that changes in 0.1 Hz HRV and BRS during resonance breathing positively correlate with increases in interoceptive accuracy. Our results show that the extent to which breathing recruits the resonant properties of the cardiovascular system can facilitate the conscious perception of participants' heartbeats. We interpret this as an increase in vagal afferent signaling and baroreflex functioning following resonance breathing. We put forward an alternative explanation that HRV modulation can reduce interoceptive prediction errors, facilitating the conscious perception of interoceptive signals, and consider the role of resonance breathing on mental health from an interoceptive inference perspective.