Cortical processing of breathing perceptions in the athletic brain

Cognitive and neural basis of vigilance advantage in soccer players: Evidence from the drift-diffusion model and magnetic resonance imaging

Soccer is a sport that requires athletes to be constantly aware of rapidly changing and unpredictable environments and to react adaptively. Previous studies have found that soccer players typically exhibit a vigilance advantage, but the underlying cognitive and neural basis for this is unclear. In this study, 27 soccer players, 17 age-matched artistic gymnasts, and 57 college students were recruited to participate in a psychomotor vigilance task. Compared to the college students, the soccer players demonstrated higher vigilance, whereas the artistic gymnasts did not. Drift-Diffusion Modeling revealed that soccer players' non-decision time was significantly lower than that of college students, while drift rate and boundary were not significantly different between the two groups. This suggests that the vigilance advantage of soccer players stems from their shorter information encoding and action generation time. Vigilance was not only correlated with Right Ventral lateral (rtVL), Left Intralaminar (ltIL), Left Mediodorsal medial magnocellular (ltMDm) and Right Mediodorsal medial mag-no-cellular (rtMDm) thalamic subregions, and also correlates with the functional connectivity be-tween the thalamic subregions of rtVL and Right Intralaminar (rtIL), and rtVL and Left Ventral anterior (ltVA). And, rtVL may be an important region of vigilance dominance in soccer players. This finding not only helps to deepen the understanding of the computational process of vigilance in players, but also provides a reference for subsequent more in-depth studies of neural computational mechanisms.

Multidimensional assessment of exertional dyspnea in young healthy males and females who select unsatisfied inspiration at peak exercise

Historically, it was thought that healthy humans predominantly described their breathing as a sense of increased work or effort (W/E) during maximal exercise. However, emerging data show that many healthy adults select unpleasant dyspnea descriptors such as "unsatisfied inspiration" (UI), with relatively more females selecting UI than males. We hypothesized that males and females who select UI would report higher dyspnea intensity ratings during exercise, select more distressing dyspnea qualities post exercise, and have greater inspiratory constraints than those who do not. Sixty-four healthy, nonsmokers (32 males:32 females; 23 ± 5 yr) completed questionnaires, pulmonary function tests, and maximal incremental cycling with detailed dyspnea evaluation. Males in UI and non-UI subgroups reported similar Borg 0-10 dyspnea intensity ratings of W/E, UI, and unsatisfied expiration (UE) (all P > 0.05). Females in the UI subgroup reported significantly higher UI and UE ratings than females in the non-UI subgroup (both P < 0.01). Both UI subgroups reported greater air hunger, chest tightness, and mental breathing effort than non-UI participants (all P < 0.05). In males only, masculine gender was negatively correlated (ρ = -0.402, P = 0.02) and anxiety positively correlated (ρ = 0.363, P = 0.04) with submaximal UI ratings. Females with UI had smaller peak tidal volume (Vt) [1.74 (0.32) vs. 2.06 (0.33) L, P = 0.03] than non-UI females; and Vt was negatively correlated with submaximal (ρ = -0.496, P = 0.004) and peak (ρ = -0.495, P = 0.004) UI ratings in all females. There were no differences in Vt or correlations between Vt and dyspnea in male subgroups. Absolute lung volumes and psychosocial factors appear important in understanding sex differences in the perception of UI during exercise.NEW & NOTEWORTHY The mechanisms of sex-based differences in the sensation of unsatisfied inspiration (UI) in healthy humans during exercise are poorly understood. We found that females who selected UI at peak exercise had worse dyspnea intensity ratings throughout exercise. Both sexes who selected UI at peak exercise also reported more distressing dyspnea qualities post exercise. Psychosocial factors appeared to influence male dyspnea perception, whereas smaller absolute lung volumes correlated with worse UI ratings in females.

Deep brain stimulation of the motor thalamus relieves experimentally induced air hunger

RESEARCH QUESTION

We previously reported that deep brain stimulation (DBS) of the motor thalamus, in a patient with post-stroke tremor, relieved breathlessness associated with COPD. This raised the question of whether motor thalamus DBS mitigates the ascending dyspnoea signal. We therefore sought to conduct a fully powered cohort study of experimentally induced air hunger, an uncomfortable urge to breathe in patients with motor thalamus DBS "ON" and "OFF".

METHODS

16 patients (three females) with DBS of the ventral intermediate nucleus (VIM) as treatment for tremor underwent hypercapnic air hunger tests, with DBS ON and OFF. Patients rated air hunger on a visual analogue scale (VAS) every 15 s. Hypercapnia and ventilation were matched for ON and OFF states (end-tidal carbon dioxide tension mean±sd 43±4 and 43±4 mmHg, respectively; ventilation 13.7 and 13.4 L·min-1, respectively). Participants' ventilation was constrained to baseline levels by breathing from a 3-L inspiratory reservoir with fixed flow of fresh gas while targeting their resting breathing frequency to a metronome.

RESULTS

Overall steady-state air hunger was 52±28%VAS for ON and 67±20%VAS for OFF (p=0.002; two-tailed paired t-test). The mean reduction in air hunger during VIM DBS was -14.4%VAS. DBS of the motor thalamus relieved air hunger in 13 patients, heightened air hunger in two and caused no change in one.

CONCLUSION

DBS of the motor thalamus for tremor relief also mitigates the air hunger component of dyspnoea. We posit that DBS of the motor thalamus heightens the gating control of the thalamus modulating the ascending air hunger signal. Extent of relief suggests that thalamic DBS may prove to be a viable therapy for intractable dyspnoea.

From Lung to Brain: Respiration Modulates Neural and Mental Activity

Respiration protocols have been developed to manipulate mental states, including their use for therapeutic purposes. In this systematic review, we discuss evidence that respiration may play a fundamental role in coordinating neural activity, behavior, and emotion. The main findings are: (1) respiration affects the neural activity of a wide variety of regions in the brain; (2) respiration modulates different frequency ranges in the brain's dynamics; (3) different respiration protocols (spontaneous, hyperventilation, slow or resonance respiration) yield different neural and mental effects; and (4) the effects of respiration on the brain are related to concurrent modulation of biochemical (oxygen delivery, pH) and physiological (cerebral blood flow, heart rate variability) variables. We conclude that respiration may be an integral rhythm of the brain's neural activity. This provides an intimate connection of respiration with neuro-mental features like emotion. A respiratory-neuro-mental connection holds the promise for a brain-based therapeutic usage of respiration in mental disorders.

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.

The Effects of Respiratory Muscle Training on Resting-State Brain Activity and Thoracic Mobility in Healthy Subjects: A Randomized Controlled Trial

BACKGROUND

Although inspiratory muscle training (IMT) is an effective intervention for improving breath perception, brain mechanisms have not been studied yet.

PURPOSE

To examine the effects of IMT on insula and default mode network (DMN) using resting-state functional MRI (RS-fMRI).

STUDY TYPE

Prospective.

POPULATION

A total of 26 healthy participants were randomly assigned to two groups as IMT group (n = 14) and sham IMT groups (n = 12).

FIELD STRENGTH/SEQUENCE

A 3-T, three-dimensional T2* gradient-echo echo planar imaging sequence for RS-fMRI was obtained.

ASSESSMENT

The intervention group received IMT at 60% and sham group received at 15% of maximal inspiratory pressure (MIP) for 8 weeks. Pulmonary and respiratory muscle function, and breathing patterns were measured. Groups underwent RS-fMRI before and after the treatment.

STATISTICAL TESTS

Statistical tests were two-tailed P < 0.05 was considered statistically significant. Student's t test was used to compare the groups. One-sample t-test for each group was used to reveal pattern of functional connectivity. A statistical threshold of P < 0.001 uncorrected value was set at voxel level. We used False discovery rate (FDR)-corrected P < 0.05 cluster level.

RESULTS

The IMT group showed more prominent alterations in insula and DMN connectivity than sham group. The MIP was significantly different after IMT. Respiratory rate (P = 0.344), inspiratory time (P = 0.222), expiratory time (P = 1.000), and inspiratory time/total breath time (P = 0.572) of respiratory patterns showed no significant change after IMT. All DMN components showed decreased, while insula showed increased activation significantly.

DATA CONCLUSION

Differences in brain activity and connectivity may reflect improved ventilatory perception with IMT with a possible role in regulating breathing pattern by processing interoceptive signals.

EVIDENCE LEVEL

2 TECHNICAL EFFICACY: Stage 4.

Breathing control, brain, and bodily self-consciousness: Toward immersive digiceuticals to alleviate respiratory suffering

Breathing is peculiar among autonomic functions through several characteristics. It generates a very rich afferent traffic from an array of structures belonging to the respiratory system to various areas of the brain. It is intimately associated with bodily movements. It bears particular relationships with consciousness as its efferent motor control can be automatic or voluntary. In this review within the scope of "respiratory neurophysiology" or "respiratory neuroscience", we describe the physiological organisation of breathing control. We then review findings linking breathing and bodily self-consciousness through respiratory manipulations using virtual reality (VR). After discussing the currently admitted neurophysiological model for dyspnea, as well as a new Bayesian model applied to breathing control, we propose that visuo-respiratory paradigms -as developed in cognitive neuroscience- will foster insights into some of the basic mechanisms of the human respiratory system and will also lead to the development of immersive VR-based digital health tools (i.e. digiceuticals).

Perceptual and Ventilatory Responses to Hypercapnia in Athletes and Sedentary Individuals

Purpose

Hypercapnic chemosensitivity traditionally captures the ventilatory response to elevated pressures of carbon dioxide in the blood. However, hypercapnia also contributes to subjective breathing perceptions, and previously we demonstrated a closer matching of perception to changes in ventilation in athletes compared to controls. Here we investigated any potential underlying hypercapnic chemosensitivity differences between groups, and explored whether these measures relate to ventilatory and perceptual responses during exercise as well as trait levels of affect.

Methods

A hypercapnic challenge, incremental maximal exercise test and affective questionnaires were completed by 20 endurance athletes and 20 age-/sex-matched sedentary controls. The hypercapnic challenge involved elevating end-tidal PCO₂ by 0.8% (6.1 mmHg) and 1.5% (11.2 mmHg) for 3 min each (randomised), with constant end-tidal oxygen. Ventilatory and perceptual responses to hypercapnia were compared between groups, and within each group the relationships between hypercapnic chemosensitivity (slope analyses) and exercising ventilation and perceptions were calculated using Spearman’s non-parametric correlations.

Results

While absolute ventilation differences during hypercapnia and exercise were observed, no group differences were found across hypercapnic chemosensitivity (slope) measures. Correlation analyses revealed the anxiety hypercapnic response was related to maximal exercise anxiety, but only in sedentary individuals.

Conclusion

Ventilatory and perceptual hypercapnic chemosensitivity do not differ between athletes and sedentary individuals. However, ventilatory and anxiety hypercapnic chemosensitivities were related to ventilatory and anxiety responses during exercise in untrained individuals only. Athletes may employ additional strategies during exercise to reduce the influence of chemosensitivity on ventilatory and perceptual responses.

Baseline Psychological Traits Contribute to Lake Louise Acute Mountain Sickness Score at High Altitude

Talks, Benjamin James, Catherine Campbell, Stephanie J. Larcombe, Lucy Marlow, Sarah L. Finnegan, Christopher T. Lewis, Samuel J.E. Lucas, Olivia K. Harrison, and Kyle T.S. Pattinson. Baseline psychological traits contribute to Lake Louise Acute Mountain Sickness score at high altitude. High Alt Med Biol. 23:69-77, 2022. Background: Interoception refers to an individual's ability to sense their internal bodily sensations. Acute mountain sickness (AMS) is a common feature of ascent to high altitude that is only partially explained by measures of peripheral physiology. We hypothesized that interoceptive ability may explain the disconnect between measures of physiology and symptom experience in AMS. Methods: Two groups of 18 participants were recruited to complete a respiratory interoceptive task three times at 2-week intervals. The control group remained in Birmingham (140 m altitude) for all three tests. The altitude group completed test 1 in Birmingham, test 2 the day after arrival at 2,624 m, and test 3 at 2,728 m after an 11-day trek at high altitude (up to 4,800 m). Results: By measuring changes to metacognitive performance, we showed that acute ascent to altitude neither presented an interoceptive challenge, nor acted as interoceptive training. However, AMS symptom burden throughout the trek was found to relate to sea level measures of anxiety, agoraphobia, and neuroticism. Conclusions: This suggests that the Lake Louise AMS score is not solely a reflection of physiological changes on ascent to high altitude, despite often being used as such by researchers and commercial trekking companies alike.

Dyspnea

The clinical term dyspnea (a.k.a. breathlessness or shortness of breath) encompasses at least three qualitatively distinct sensations that warn of threats to breathing: air hunger, effort to breathe, and chest tightness. Air hunger is a primal homeostatic warning signal of insufficient alveolar ventilation that can produce fear and anxiety and severely impacts the lives of patients with cardiopulmonary, neuromuscular, psychological, and end-stage disease. The sense of effort to breathe informs of increased respiratory muscle activity and warns of potential impediments to breathing. Most frequently associated with bronchoconstriction, chest tightness may warn of airway inflammation and constriction through activation of airway sensory nerves. This chapter reviews human and functional brain imaging studies with comparison to pertinent neurorespiratory studies in animals to propose the interoceptive networks underlying each sensation. The neural origins of their distinct sensory and affective dimensions are discussed, and areas for future research are proposed. Despite dyspnea's clinical prevalence and impact, management of dyspnea languishes decades behind the treatment of pain. The neurophysiological bases of current therapeutic approaches are reviewed; however, a better understanding of the neural mechanisms of dyspnea may lead to development of novel therapies and improved patient care.

Interoception of breathing and its relationship with anxiety

Interoception, the perception of internal bodily states, is thought to be inextricably linked to affective qualities such as anxiety. Although interoception spans sensory to metacognitive processing, it is not clear whether anxiety is differentially related to these processing levels. Here we investigated this question in the domain of breathing, using computational modeling and high-field (7 T) fMRI to assess brain activity relating to dynamic changes in inspiratory resistance of varying predictability. Notably, the anterior insula was associated with both breathing-related prediction certainty and prediction errors, suggesting an important role in representing and updating models of the body. Individuals with low versus moderate anxiety traits showed differential anterior insula activity for prediction certainty. Multi-modal analyses of data from fMRI, computational assessments of breathing-related metacognition, and questionnaires demonstrated that anxiety-interoception links span all levels from perceptual sensitivity to metacognition, with strong effects seen at higher levels of interoceptive processes.

Air Hunger: A Primal Sensation and a Primary Element of Dyspnea

The sensation that develops as a long breath hold continues is what this article is about. We term this sensation of an urge to breathe "air hunger." Air hunger, a primal sensation, alerts us to a failure to meet an urgent homeostatic need maintaining gas exchange. Anxiety, frustration, and fear evoked by air hunger motivate behavioral actions to address the failure. The unpleasantness and emotional consequences of air hunger make it the most debilitating component of clinical dyspnea, a symptom associated with respiratory, cardiovascular, and metabolic diseases. In most clinical populations studied, air hunger is the predominant form of dyspnea (colloquially, shortness of breath). Most experimental subjects can reliably quantify air hunger using rating scales, that is, there is a consistent relationship between stimulus and rating. Stimuli that increase air hunger include hypercapnia, hypoxia, exercise, and acidosis; tidal expansion of the lungs reduces air hunger. Thus, the defining experimental paradigm to evoke air hunger is to elevate the drive to breathe while mechanically restricting ventilation. Functional brain imaging studies have shown that air hunger activates the insular cortex (an integration center for perceptions related to homeostasis, including pain, food hunger, and thirst), as well as limbic structures involved with anxiety and fear. Although much has been learned about air hunger in the past few decades, much remains to be discovered, such as an accepted method to quantify air hunger in nonhuman animals, fundamental questions about neural mechanisms, and adequate and safe methods to mitigate air hunger in clinical situations. © 2021 American Physiological Society. Compr Physiol 11:1449-1483, 2021.

Multidimensional breathlessness response to exercise: Impact of COPD and healthy ageing

This study compared the multidimensional breathlessness response to incremental cardiopulmonary cycle exercise testing (CPET) in people with chronic obstructive pulmonary disease (COPD; n = 14, aged 69 ± 9 years, forced expiratory volume in 1-sec = 54 ± 16 % predicted) and healthy older (OA) (n = 35, aged 68 ± 5 years) and younger (YA) (n = 19, aged 28 ± 8 years) adults. Participants performed CPET and successively rated overall breathlessness intensity, unsatisfied inspiration, breathing too shallow, work/effort of breathing, and breathlessness-related unpleasantness, fear, and anxiety using the 0-10 Borg scale. At any given percent predicted peak minute ventilation, people with COPD rated all breathlessness sensations higher than OA and YAs, who were similar. Most between group differences disappeared when examined in relation to inspiratory reserve volume, except people with COPD reported higher levels of unsatisfied inspiration and breathing too shallow (vs YA), and breathlessness-related fear and anxiety (vs OA and YAs). Multidimensional ratings of breathlessness sensations during CPET provides further insight into differences in exertional symptom perceptions among people with COPD and without COPD.

Attention to breath sensations does not engage endogenous opioids to reduce pain

The endogenous opioidergic system is critically involved in the cognitive modulation of pain. Slow-breathing-based techniques are widely used nonpharmacological approaches to reduce pain. Yet, the active mechanisms of actions supporting these practices are poorly characterized. Growing evidence suggest that mindfulness-meditation, a slow-breathing technique practiced by nonreactively attending to breathing sensations, engages multiple unique neural mechanisms that bypass opioidergically mediated descending pathways to reduce pain. However, it is unknown whether endogenous opioids contribute to pain reductions produced by slow breathing. The present double-blind, placebo-controlled crossover study examined behavioral pain responses during mindfulness-meditation (n = 19), sham-mindfulness meditation (n = 20), and slow-paced breathing (n = 20) in response to noxious heat (49°C) and intravenous administration (0.15 mg/kg bolus + 0.1 mg/kg/hour maintenance infusion) of the opioid antagonist, naloxone, and placebo saline. Mindfulness significantly reduced pain unpleasantness ratings across both infusion sessions when compared to rest, but not pain intensity. Slow-paced breathing significantly reduced pain intensity and unpleasantness ratings during naloxone but not saline infusion. Pain reductions produced by mindfulness-meditation and slow-paced breathing were insensitive to naloxone when compared to saline administration. By contrast, sham-mindfulness meditation produced pain unpleasantness reductions during saline infusion but this effect was reversed by opioidergic antagonism. Sham-mindfulness did not lower pain intensity ratings. Self-reported "focusing on the breath" was identified as the operational feature particularly unique to the mindfulness-meditation and slow paced-breathing, but not sham-mindfulness meditation. Across all individuals, attending to the breath was associated with naloxone insensitive pain-relief. These findings provide evidence that slow breathing combined with attention to breath reduces pain independent of endogenous opioids.

En Pointe: Dancers Report Their Pain Less Variably Than Do Controls

The subjective nature of pain and the lack of a gold standard for objective measurement hinders effective assessment, diagnosis, and treatment. Some individuals, such as professional dancers, are better in assessing and reporting bodily sensations. This observational study aimed to assess whether dancers report their pain less variably, than other people do. After consenting, subjects completed the focused analgesia selection test (FAST), which assesses subjects' variability of pain reports. FAST outcomes, ICC and R² reflect the magnitude of variability of pain reports observed. In addition, subjects underwent a taste task, which similarly assesses variability of tastes (salty and sweet) intensity reports and completed the Multidimensional Assessment of Interoceptive Awareness questionnaire. Thirty-three professional dancers and 33 healthy aged-matched controls were recruited. The dancers exhibited less variability of pain reports then controls (P = .013), but not in case of tastes-reports. Years of practice was positively correlated with pain reporting variability (r = .447, P = .009, and r = .380, P = .029; for FAST ICC and R², respectively). Multidimensional Assessment of Interoceptive Awareness subscores correlated with pain reporting variability: R² and ICC with emotional awareness (r = .260, P = .040, and r = .274, P = .030, respectively), and R² with trusting [r = .254, P = .044]). PERSPECTIVE: The difference between dancers and controls in the magnitude of variability of pain reports is probably due to the dancers' extensive training, which focuses on attention to body signals. Our results suggest that training can improve subjective pain reports, which are essential for quality clinical care.

Neural Efficiency and Acquired Motor Skills: An fMRI Study of Expert Athletes

The neural efficiency hypothesis was investigated. Functional magnetic resonance imaging was used to study the differences in brain activity between athletes imagining performing different movements: basketball athletes imagined throwing and volleyball athletes imagined serving. These comparisons of brain activity among athletes imagining movements from their self-sport (e.g., a basketball throw in basketball athletes) versus movements from other sport (e.g., a volleyball serve in basketball athletes) revealed the neural energy consumption each task costs. The results showed better temporal congruence between motor execution and motor imagery and vividness of motor imagery, but lower levels of activation in the left putamen, inferior parietal lobule, supplementary motor area, postcentral gyrus, and the right insula when both groups of athletes imagined movements from their self-sport compared with when they imagined movements from the other-sport. Athletes were more effective in the representation of the motor sequences and the interoception of the motor sequences for their self-sport. The findings of present study suggest that elite athletes achieved superior behavioral performance with minimal neural energy consumption, thus confirming the neural efficiency hypotheses.