Closing the brain-heart loop: Towards more holistic models of addiction and addiction recovery.

Much research seeks to articulate the brain structures and pathways implicated in addiction and addiction recovery. Prominent neurobiological models emphasize the interplay between cortical and limbic brain regions as a main driver of addictive processes, but largely do not take into consideration sensory and visceral information streams that link context and state to the brain and behavior. Yet these brain-body information streams would seem to be necessary elements of a comprehensive model of addiction. As a starting point, we describe the overlap between one current model of addiction circuitry and the neural network that not only regulates cardiovascular system activity but also receives feedback from peripheral cardiovascular processes through the baroreflex loop. We highlight the need for neurobiological, molecular, and behavioral studies of neural and peripheral cardiovascular signal integration during the experience of internal states and environmental contexts that drive alcohol and other drug use behaviors. We end with a call for systematic, mechanistic research on the promising, yet largely unexamined benefits to addiction treatment of neuroscience-informed, adjunctive interventions that target the malleability of the cardiovascular system to alter brain processes.

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

Interoceptive signals give rise to subjective feeling states that can drive motivational and behavioural responses. In the context of alcohol use behaviours, interoceptive signals may shape subjective alcohol experiences and thereby support biobehavioural mechanisms of drinking behaviour change. This study examined the acute effects of alcohol on participants' interoceptive abilities and determined whether pharmacologically induced changes in heart beat detection correlate with subjective alcohol effects, craving and expectancies. Participants completed a two-session, double-blind placebo controlled experiment (n = 27). Participants consumed a beverage containing 0.4 g/kg of alcohol or a placebo. They also completed measurements of alcohol expectancies at baseline, and alcohol-induced changes in mood, craving and light-headedness. Interoceptive ability was measured using the heartbeat discrimination task prior to and following beverage administration, yielding indices of interoceptive accuracy, confidence and meta-cognition. Alcohol administration increased interoceptive accuracy compared with baseline and placebo; and those changes in interoception negatively correlated with negative alcohol expectancies. Further, changes in interoception positively correlated with perceived light-headedness and positive mood after alcohol administration, whereas null effects were found for craving. In the placebo condition, null results were obtained. Alcohol is well established to change bodily states, and here, we find that the extent to which alcohol increases participants' sensitivity to bodily states correlates with their subjective drinking experiences. This was observed in relation to mood, light-headedness and prospective alcohol expectancies. We posit that over successive alcohol experiences, changes in bodily states may feed into the development of alcohol expectancies that could in turn predict future drinking behaviours.

More than meets the heart: systolic amplification of different emotional faces is task dependent.

Interoceptive processes emanating from baroreceptor signals support emotional functioning. Previous research suggests a unique link to fear: fearful faces, presented in synchrony with systolic baroreceptor firing draw more attention and are rated as more intense than those presented at diastole. This study examines whether this effect is unique to fearful faces or can be observed in other emotional faces. Participants (n = 71) completed an emotional visual search task (VST) in which fearful, happy, disgust and sad faces were presented during systolic and diastolic phases of the cardiac cycle. Visual search accuracy and emotion detection accuracy and latency were recorded, followed by a subjective intensity task. A series of interactions between emotion and cardiac phase were observed. Visual search accuracy for happy and disgust faces was greater at systole than diastole; the opposite was found for fearful faces. Fearful and happy faces were perceived as more intense at systole. Previous research proposed that cardiac signalling has specific effects on the attention and intensity ratings for fearful faces. Results from the present tasks suggest these effects are more generalised and raise the possibility that interoceptive signals amplify emotional superiority effects dependent on the task employed.

Getting to the Heart of Low Sensitivity to Alcohol: Context Moderates Low Cardiovascular Response to Alcohol in Persons With a Family History of Alcohol Use Disorder.

BACKGROUND: Low sensitivity to alcohol in persons with a family history of alcoholism (FH+), compared to those without (FH-), contributes to risk for alcohol use disorder (AUD). However, sensitivity of FH+ cardiovascular response to alcohol is not well understood. This gap is significant because cardiovascular processes contribute to emotional regulation and stress response problems theorized to be central to the development and persistence of AUD. This study compared changes in heart rate (HR) and HR variability (HRV) between FH groups after consuming alcohol and control beverages and examined how these changes were moderated by emotional and alcohol-related contexts. METHODS: Young adults (N = 165) with FH+ (n = 110) or FH- (n = 55) each completed 2 sessions, separated by 1 week. They received one of 3 different beverages (alcohol, placebo, and told-no-alcohol) in each session. Electrocardiogram data were recorded during pre-beverage consumption and post-beverage consumption baselines, and then during 4 picture cue tasks (neutral, positive, negative, and alcohol-related). Generalized estimating equations were used to examine differences in cardiovascular reactivity (changes in HR and HRV power at ~ 0.1 Hz) across FH groups, beverage conditions, and picture cue tasks. RESULTS: A significant beverage condition × cue task × FH interaction effect on HRV was observed. The FH+ group, compared to the FH- group, showed (a) significantly less HRV suppression in specific cue contexts following alcohol, (b) a mixed pattern of more and less HRV suppression across cue contexts following placebo, and (c) a similar HRV reactivity pattern in the told-no-alcohol condition across cue tasks. For HR, there were no significant effects involving FH. CONCLUSIONS: Diminished cardiovascular sensitivity to oral alcohol in FH+ persons varied within a given drinking episode depending on emotional and alcohol-related features of the context, suggesting that environmental characteristics play a role in the expression of low sensitivity to alcohol among FH+ individuals.

Immediate and Complex Cardiovascular Adaptation to an Acute Alcohol Dose.

BACKGROUND: The detrimental effects of chronic heavy alcohol use on the cardiovascular system are well established and broadly appreciated. Integrated cardiovascular response to an acute dose of alcohol has been less studied. This study examined the early effects of an acute dose of alcohol on the cardiovascular system, with particular emphasis on system variability and sensitivity. The goal was to begin to understand how acute alcohol disrupts dynamic cardiovascular regulatory processes prior to the development of cardiovascular disease. METHODS: Healthy participants (N = 72, age 21 to 29) were randomly assigned to an alcohol, placebo, or no-alcohol control beverage condition. Beat-to-beat heart rate (HR) and blood pressure (BP) were assessed during a low-demand cognitive task prior to and following beverage consumption. Between-group differences in neurocardiac response to an alcohol challenge (blood alcohol concentration ~ 0.06 mg/dl) were tested. RESULTS: The alcohol beverage group showed higher average HR, lower average stroke volume, lower HR variability and BP variability, and increased vascular tone baroreflex sensitivity after alcohol consumption. No changes were observed in the placebo group, but the control group showed slightly elevated average HR and BP after beverage consumption, possibly due to juice content. At the level of the individual, an active alcohol dose appeared to disrupt the typically tight coupling between cardiovascular processes. CONCLUSIONS: A dose of alcohol quickly invoked multiple cardiovascular responses, possibly as an adaptive reaction to the acute pharmacological challenge. Future studies should assess how exposure to alcohol acutely disrupts or dissociates typically integrated neurocardiac functions.

A computational physiology approach to personalized treatment models: the beneficial effects of slow breathing on the human cardiovascular system.

Heart rate variability biofeedback intervention involves slow breathing at a rate of ∼6 breaths/min (resonance breathing) to maximize respiratory and baroreflex effects on heart period oscillations. This intervention has wide-ranging clinical benefits and is gaining empirical support as an adjunct therapy for biobehavioral disorders, including asthma and depression. Yet, little is known about the system-level cardiovascular changes that occur during resonance breathing or the extent to which individuals differ in cardiovascular benefit. This study used a computational physiology approach to dynamically model the human cardiovascular system at rest and during resonance breathing. Noninvasive measurements of heart period, beat-to-beat systolic and diastolic blood pressure, and respiration period were obtained from 24 healthy young men and women. A model with respiration as input was parameterized to better understand how the cardiovascular processes that control variability in heart period and blood pressure change from rest to resonance breathing. The cost function used in model calibration corresponded to the difference between the experimental data and model outputs. A good match was observed between the data and model outputs (heart period, blood pressure, and corresponding power spectral densities). Significant improvements in several modeled cardiovascular functions (e.g., blood flow to internal organs, sensitivity of the sympathetic component of the baroreflex, ventricular elastance) were observed during resonance breathing. Individual differences in the magnitude and nature of these dynamic responses suggest that computational physiology may be clinically useful for tailoring heart rate variability biofeedback interventions for the needs of individual patients.

Mental and Physical (MAP) Training: a neurogenesis-inspired intervention that enhances health in humans.

New neurons are generated in the hippocampus each day and their survival is greatly enhanced through effortful learning (Shors, 2014). The numbers of cells produced can be increased by physical exercise (van Praag, Kempermann, & Gage, 1999). These findings inspired us to develop a clinical intervention for humans known as Mental and Physical Training, or MAP Training. Each session consists of 30min of mental training with focused attention meditation (20min sitting and 10min walking). Meditation is an effortful training practice that involves learning about the transient nature of thoughts and thought patterns, and acquiring skills to recognize them without necessarily attaching meaning and/or emotions to them. The mental training component is followed by physical training with 30min of aerobic exercise performed at moderate intensity. During this component, participants learn choreographed dance routines while engaging in aerobic exercise. In a pilot "proof-of-concept" study, we provided supervised MAP Training (2 sessions per week for 8weeks) to a group of young mothers in the local community who were recently homeless, most of them having previously suffered from physical and sexual abuse, addiction, and depression. Preliminary data suggest that MAP Training improves dependent measures of aerobic fitness (as assessed by maximal rate of oxygen consumed) while decreasing symptoms of depression and anxiety. Similar changes were not observed in a group of recently homeless women who did not participate in MAP Training. It is not currently possible to determine whether new neurons in the human brain increase in number as a result of MAP Training. Rather these preliminary results of MAP Training illustrate how neuroscientific research can be translated into novel clinical interventions that benefit human health and wellness.

Memory for drug-related visual stimuli in young adult, cocaine-dependent polydrug users.

BACKGROUND AND OBJECTIVES: Implicit (unconscious) and explicit (conscious) memory associations with drugs have been examined primarily using verbal cues. However, drug seeking, drug use behaviors, and relapse in chronic cocaine and other drug users are frequently triggered by viewing substance-related visual cues in the environment. We thus examined implicit and explicit memory for drug picture cues to understand the relative extent to which conscious and unconscious memory facilitation of visual drug cues occurs during cocaine dependence. METHODS: Memory for drug-related and neutral picture cues was assessed in 14 inpatient cocaine-dependent polydrug users and a comparison group of 21 young adults with limited drug experience (n = 35). Participants completed picture cue exposure, free recall and recognition tasks to assess explicit memory, and a repetition priming task to assess implicit memory. RESULTS: Drug cues, compared to neutral cues, were better explicitly recalled and implicitly primed, and especially so in the cocaine group. In contrast, neutral cues were better explicitly recognized, and especially in the control group. CONCLUSION: Certain forms of explicit and implicit memory for drug cues were enhanced in cocaine users compared to controls when memory was tested a short time following cue exposure. Enhanced unconscious memory processing of drug cues in chronic cocaine users may be a behavioral manifestation of heightened drug cue salience that supports drug seeking and taking. There may be value in expanding intervention techniques to utilize cocaine users' implicit memory system.

A role for cognitive rehabilitation in increasing the effectiveness of treatment for alcohol use disorders.

Neurocognitive impairments are prevalent in persons seeking treatment for alcohol use disorders (AUDs). These impairments and their physical, social, psychological and occupational consequences vary in severity across persons, much like those resulting from traumatic brain injury; however, due to their slower course of onset, alcohol-related cognitive impairments are often overlooked both within and outside of the treatment setting. Evidence suggests that cognitive impairments can impede treatment goals through their effects on treatment processes. Although some recovery of alcohol-related cognitive impairments often occurs after cessation of drinking (time-dependent recovery), the rate and extent of recovery is variable across cognitive domains and individuals. Following a long hiatus in scientific interest, a new generation of research aims to facilitate treatment process and improve AUD treatment outcomes by directly promoting cognitive recovery (experience-dependent recovery). This review updates knowledge about the nature and course of cognitive and brain impairments associated with AUD, including cognitive effects of adolescent AUD. We summarize current evidence for indirect and moderating relationships of cognitive impairment to treatment outcome, and discuss how advances in conceptual frameworks of brain-behavior relationships are fueling the development of novel AUD interventions that include techniques for cognitive remediation. Emerging evidence suggests that such interventions can be effective in promoting cognitive recovery in persons with AUD and other substance use disorders, and potentially increasing the efficacy of AUD treatments. Finally, translational approaches based on cognitive science, neurophysiology, and neuroscience research are considered as promising future directions for effective treatment development that includes cognitive rehabilitation.

Negative mood and alcohol problems are related to respiratory dynamics in young adults.

This study examined the relationship of negative affect and alcohol use behaviors to baseline respiration and respiratory response to emotional challenge in young adults (N = 138, 48 % women). Thoracic-to-abdominal ratio, respiratory frequency and variability, and minute volume ventilation were measured during a low-demand baseline task, and emotional challenge (viewing emotionally-valenced, emotionally-neutral, and alcohol-related pictures). Negative mood and alcohol problems principal components were generated from self-report measures of negative affect and mood, alcohol use, and use-related problems. The negative mood component was positively related to a thoracic bias when measured throughout the study (including baseline and picture exposure). There was generally greater respiratory activity in response to the picture cues, although not specifically in response to the content (emotional or alcohol-related) of the picture cues. The alcohol problems component was positively associated with respiratory reactivity to picture cues, when baseline breathing patterns were controlled. Self-report arousal data indicated that higher levels of negative mood, but not alcohol problems, were associated with greater arousal ratings overall. However, those with alcohol problems reported greater arousal to alcohol cues, compared to emotionally neutral cues. These results are consistent with theories relating negative affect and mood to breathing patterns as well as the relationship between alcohol problems and negative emotions, suggesting that the use of respiratory interventions may hold promise for treating problems involving negative affect and mood, as well as drinking problems.

Functional connectivity in the central executive network predicts changes in binge drinking behavior during emerging adulthood: an observational prospective study.

BACKGROUND AND AIMS: Binge drinking contributes to the immense public health burden associated with alcohol use, especially among younger drinkers. Little is known about the underlying neurobiology of changes in this behavior over time. This preliminary study aimed to identify neurobiological markers of binge drinking behavior change during emerging adulthood. DESIGN: Observational prospective investigation of neurobiological predictors of binge drinking behavior. SETTING: Communities surrounding a large, public university in the northeastern United States. PARTICIPANTS: A total of 42 emerging adults (48% female), approximately half meeting criteria for an alcohol use disorder. MEASUREMENTS: Past month binge drinking, the dependent variable, was assessed at two time-points (T1, T2) via self-report. Ten indices of resting-state functional connectivity within the central executive network (CEN), a brain network involved in executive function, were collected at T1 and specified as independent variables in cross-sectional and prospective Poisson models. All models controlled for age, sex, and alcohol use disorder status. FINDINGS: The cross-sectional model yielded five significant associations between CEN connectivity and binge drinking incidence. Connections anchored primarily in the anterior CEN exhibited negative associations with binge drinking incidence (P = 0.001, 0.004, 0.011), and connections stemming from the right posterior parietal cortex exhibited positive associations with binge drinking incidence (P = 0.041, 0.045). In prospective models, stronger frontoparietal connectivity between the right dorsolateral prefrontal cortex and left posterior parietal cortex predicted greater increases in binge drinking incidence over time (P = 0.003). CONCLUSIONS: There is an association between central executive network connectivity and heavy drinking, as well as evidence that functional pathways within the central executive network may contribute to changes in problematic drinking behaviors.

Effects of arousal modulation via resonance breathing on craving and affect in women with substance use disorder.

BACKGROUND: Craving for alcohol and other drugs is a complex in-the-moment experience that involves within-person changes in physiological arousal and affect. We evaluated the utility of a just-in-time, self-administered resonance breathing smartphone application (app) to reduce craving and improve affect in women during outpatient treatment for substance use disorders (SUD). METHODS: Women (N = 57) receiving outpatient addiction treatment were randomized to practice either cardiovascular resonance breathing (0.1 Hz/6 breaths per minute) or a sham (∼0.23 Hz/14 breaths per minute) in the face of urges over an 8-week intervention. Craving (Penn Alcohol Craving Scale) and affect (Positive and Negative Affect Scale) were collected weekly throughout the intervention. App data were uploaded weekly to assess frequency of use. Generalized Estimated Equations modeled craving and affect as a function of group randomization and app use frequency across the 8-week intervention. FINDINGS: Higher levels of craving were associated with more frequent app use. The group X app use interaction was significant for craving. Frequent app use during the intervention phase was associated with lower craving levels in the resonance breathing group relative to the sham group over the 8-week intervention. There was no effect of app use frequency on affect measures. CONCLUSIONS: Women assigned to practice sham breathing who used the intervention frequently experienced elevations in craving that are commonly reported during outpatient SUD treatment. Women assigned to resonance breathing who used the intervention frequently did not experience such increases. Resonance breathing may be protective against triggers in outpatient treatment. Physiological mechanisms are discussed.

Use and perceived usefulness of a just-in-time resonance breathing intervention adjunct for substance use disorder: Contextual and physiological predictors.

Craving for alcohol and other drugs is often described as a momentary hyperarousal state that interferes with one's ability to use top-down strategies. As such, it may be best interrupted 'in the moment' through bottom-up modulation. We recently reported that episodic resonance paced breathing (eRPB) delivered via mobile phone app as an add-on to outpatient treatment for substance use disorder (SUD) was effective at dampening craving over the course of an 8-week intervention (NCT#02579317). However, not all participants engaged with the eRPB app and there was high intra- and inter-individual variability in weekly ratings of usefulness. Here we examined baseline demographic, physiological, and psychiatric measures as well as time-varying exposure to positive, negative, and temptation craving triggers as predictors of frequency of eRPB app use and ratings of usefulness. Seventy-seven outpatient women were randomized to an eRPB (0.1 Hz) or a faster paced breathing sham (0.23 Hz) condition. Baseline measures were assessed within the first 3 weeks of treatment entry prior to randomization. App use frequency, ratings of usefulness, and trigger exposure were measured weekly throughout the intervention. Variables were entered into marginal means models with forward stepwise model selection and examined as predictors of use and usefulness. Frequent app use was associated with a lifetime alcohol use disorder (AUD) diagnosis (p = 0.026), higher ratings of usefulness (p < 0.001), and fewer exposures to positive triggers (e.g., celebration, socialization; p < 0.001). There was a trend-level association between frequency of app use and greater cardiovascular capacity at baseline (p = 0.088). Higher ratings of usefulness were associated with greater exposure to negative triggers (e.g,. loneliness, frustration; p < 0.001) and parasympathetic dysregulation at baseline (p = 0.05). A positive relationship between app use frequency and ratings of usefulness was present only in the eRPB group (p = 0.045). Matching ideal candidates and moments to an arousal modulation anti-craving intervention can help streamline screening and implementation of eRPB in the treatment of SUD. Clinical Trial Registration: https://clinicaltrials.gov/ct2/show/NCT02579317, identifier NCT02579317.

Associations between heavy drinking and changes in impulsive behavior among adolescent boys.

BACKGROUND: Impulsive behavior in humans predicts the onset of drinking during adolescence and alcohol use disorders (AUDs) in adulthood. It is also possible, however, that heavy drinking may increase impulsive behavior by affecting the development of brain areas that support behavioral control or through other associated mechanisms. This study examined whether drinking heavily during adolescence is related to changes in impulsive behavior with a specific focus on how the association differs across individuals, contingent on the developmental course of their impulsiveness. METHOD: Data came from a sample of boys (N = 503) who were followed annually from approximate age 8 to age 18 and again at approximate age 24/25. Heavy drinking was defined as experiencing a blood alcohol concentration (BAC) level of 0.08% or higher. At each assessment, the parent and child each reported whether the child was impulsive. RESULTS: First, group-based trajectory analysis was used to identify 4 groups differing in the level and slopes of their trajectories of impulsive behavior from age 9 to age 17: low (13.9%), early adolescence-limited (18.7%), moderate (60.8%), and high (6.6%). These trajectory groups differed in their prevalence of any heavy drinking, peak BACs, and rates of alcohol dependence in adolescence and AUD in early adulthood, with the less impulsive groups being lower on these measures than the more impulsive groups. Heavy drinking was then entered into the model as a time-varying covariate; this measure was lagged so that the results represent change in impulsive behavior the year following heavy drinking. Among boys on the moderate trajectory, those who drank heavily were rated as significantly more impulsive the following year compared to those who did not drink heavily. CONCLUSIONS: The association between heavy drinking and impulsive behavior may depend on earlier levels of impulsive behavior with those who are moderately impulsive appearing to be at greatest risk for increased impulsive behavior following heavy drinking. Further research is needed to clarify this association.

Does alcohol affect emotional face processing via interoceptive pathways?

BACKGROUND: Our brain uses interoceptive signals from the body to shape how we perceive emotions in others; however, whether interoceptive signals can be manipulated to alter emotional perceptions is unknown. Alcohol has acute effects both on emotional processing and on the physiological substrates supporting interoception. In this registered report, we examine whether alcohol administration triggers physiological changes that alter interoceptive signals and manipulate emotional face processing. Such knowledge will broaden understanding of the mechanisms by which alcohol affects emotional face processing. METHODS: Participants (n = 36) will be administered an alcohol or placebo beverage. Cardiovascular physiology will be recorded before and after administration. Participants will complete two behavioral tasks in which they view emotional faces presented in synchrony with different phases of the cardiac cycle (i.e., systole, diastole). This manipulation creates an index of how interoceptive signals amplify emotional face processing. HYPOTHESES: We hypothesize that, compared to placebo, alcohol administration will disrupt the cardiac amplification of emotional face processing. We further explore whether this disruption depends on the nature and magnitude of changes in cardiovascular physiology after alcohol administration.

SUBSTANCE USE AND ADDICTION AFFECT MORE THAN THE BRAIN: THE PROMISE OF NEUROCARDIAC INTERVENTIONS.

Purpose of Review: Addiction and excessive substance use contribute to poor mental and physical health. Much research focuses tightly on neural underpinnings and centrally-acting interventions. To broaden this perspective, this review focuses on bidirectional pathways between the brain and cardiovascular system that are well-documented and provide innovative, malleable targets to bolster recovery and alter substance use behaviors. Recent Findings: Cardiovascular signals are integrated via afferent pathways in networks of distributed brain regions that contribute to cognition, as well as emotion and behavior regulation, and are key antecedents and drivers of substance use behaviors. Heart rate variability (HRV), a biomarker of efficient neurocardiac regulatory control, is diminished by heavy substance use and substance use disorders. Promising evidence-based adjunctive interventions that enhance neurocardiac regulation include HRV biofeedback, resonance paced breathing, and some addiction medications. Summary: Cardiovascular communication with the brain through bidirectional pathways contributes to cognitive and emotional processing but is rarely discussed in addiction treatment. New evidence supports cardiovascular-focused adjunctive interventions for problematic substance use and addiction.

An interoceptive basis for alcohol priming effects.

RATIONALE: Alcohol priming can modulate the value of rewards, as observed through the effects of acute alcohol administration on cue reactivity. However, little is known about the psychophysiological mechanisms driving these effects. Here, we examine how alcohol-induced changes in bodily states shape the development of implicit attentional biases and explicit cue reactivity. OBJECTIVES: To characterize the interoceptive correlates of alcohol priming effects on alcohol attentional biases and cue reactivity. METHODS: In a two-session double-blind alcohol administration procedure, participants (n=31) were given a 0.4-g/kg dose of alcohol or a placebo drink. Cardiovascular responses were measured before and after alcohol administration to observe the effects of alcohol on viscero-afferent reactivity, as indexed through changes in heart rate variability (HRV) at or near 0.1 Hz (0.1-Hz HRV). Next, participants completed a modified flanker task to examine implicit alcohol attentional biases and provided subjective valence and arousal ratings of alcohol cues to examine explicit cue reactivity. RESULTS: We found that changes in 0.1-Hz HRV after alcohol administration positively correlated with attentional biases, and negatively correlated with alcohol valence ratings; blood alcohol content was a null predictor. CONCLUSIONS: This is novel evidence that suggests alcohol-induced changes in bodily states may mediate the occurrence of alcohol priming effects and highlights the potentially generative role of interoceptive mechanisms in alcohol-related behaviors. The differential patterns revealed by implicit biases and explicit response tendencies are considered within the context of the dissociation between wanting and liking.

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.

Digital neuropsychological test performance in a large sample of uninjured collegiate athletes.

Digital neuropsychological test batteries are popular in college athletics; however, well-validated digital tests that are short and portable are needed to expand the feasibility of performing cognitive testing quickly, reliably, and outside standard clinical settings. This study assessed performance on digital versions of Trail Making Test (dTMT) and a modified Symbol Digit Modalities Test (dSDMT) in uninjured collegiate athletes (n = 537; 47% female) using the C3Logix baseline assessment module. Time to complete (dTMT) and the number of correct responses (dSDMT) were computed, transformed into z scores, and compared to age-matched normative data from analogous paper-and-pencil tests. Overall sample performance was compared to normative sample performance using Cohen's d. Sample averages on the dTMT, Part A, and dSDMT were similar to published norms; 97 and 92% of z scores fell within 2 standard deviations of normative means, respectively. The sample averaged faster completion times on dTMT, Part B than published norms, although 98% of z scores were within 2 standard deviations of the normative means. Brief, digitized tests may be useful in populations and testing environments when longer cognitive test batteries are impractical. Future studies should assess the ability of these tests to detect clinically relevant changes following a suspected head injury.