Nasal Respiration Entrains Human Limbic Oscillations and Modulates Cognitive Function

Effects of cardiac and respiratory phases on auditory evoked potentials

Brain-body interactions play a crucial role in the perceptual and cognitive processing of external stimuli. Previous research has examined how cardiac phases (systole, diastole) and respiratory phases (inhalation, exhalation) influence various psychological functions, though findings on their impact on auditory processing remain inconsistent. This study investigated whether cardiac and respiratory phases affect auditory ERP components, specifically N1 and P2. To control for cardiac-related artifacts, pure tones (70 dB) and silent stimuli (0 dB) were presented in alternating, randomized intervals, and ERP difference waveforms were computed by subtracting waveforms elicited by silent stimuli from those elicited by tones. Two experiments were conducted with different participants: watching a video while ignoring the tones (Experiment 1) or pressing a button as quickly as possible in response to the tones while watching the video (Experiment 2). Results showed no significant differences in N1 amplitude between cardiac or respiratory phases. P2 amplitude was significantly larger at diastole than systole, although the effect size was small (dz = 0.26). For respiratory phases, P2 amplitude was greater during exhalation than inhalation when participants ignored the tones (dz = 0.35), but this effect disappeared when they attended to the tones. These findings suggest that visceral afferent signals may influence auditory processing by modulating attentional resource allocation across different cardiac and respiratory phases.

Computational Approaches for Uncovering Interoceptive Mechanisms in Psychiatric Disorders and Their Biological Basis

Interoception, the process of detecting, perceiving, and interpreting signals from within the body, is essential for physiological regulation and adaptive behavior. A growing body of research underscores important potential links between interoceptive dysfunction and psychiatric disorders. Parallel advancements in the field of computational psychiatry have led to the development of biologically plausible models of information processing in the brain. This review surveys the current state of traditional and computational research approaches to study interoceptive processes in psychiatry. We also provide a foundational description of predominant computational approaches and theoretical models of interoception. Finally, we discuss the potential molecular foundations of interoceptive computation and consider future directions for incorporating computational models to enhance clinical insights and inform personalized treatments. We conclude that combining interoception and computational modeling approaches holds considerable promise in moving the field forward, both in addressing unresolved mechanistic questions and identifying novel potential therapeutic targets.

The pupillary respiratory-phase response: pupil size is smallest around inhalation onset and largest during exhalation

Respiration shapes brain activity and synchronizes sensory and exploratory motor actions, with some evidence suggesting that it also affects pupil size. However, evidence for a coupling between respiration and pupil size remains scarce and inconclusive, hindered by small sample sizes and limited controls. Given the importance of pupil size in visual perception and as a reflection of brain state, understanding its relationship with respiration is essential. In five experiments using a pre-registered protocol, we systematically investigated how respiratory phase affects pupil size across different conditions. In Experiment 1 (n = 50), we examined nasal and oral breathing at rest under dim lighting with nearby fixation points, then replicated these results under identical conditions in Experiment 2 (n = 53). Experiment 3 (n = 112) extended this to active visual tasks, while Experiment 4 (n = 57) extended this to controlled breathing at different paces under ambient lighting with distant fixation. Finally, in Experiment 5 (n = 34), individuals with isolated congenital anosmia (born without olfactory bulbs) were used as a lesion-type model during visual-auditory tasks to assess whether the respiratory-pupil link depends on olfactory bulb-driven oscillations. Across all conditions - free and controlled breathing; different tasks, lighting and fixation distances; and with and without olfactory bulbs - we consistently found that pupil size is smallest around inhalation onset and largest during exhalation. We term this effect the pupillary respiratory-phase response, the fourth known mechanism influencing pupil size, alongside the pupillary light, near fixation and psychosensory responses. KEY POINTS: The influence of respiration on pupil size dynamics has long been debated. In this study, we systematically investigated how pupil size changes across the breathing cycle through a series of five experiments, while varying tasks, lighting, fixation distance and brain region involvement. We show that pupil size is smallest around inhalation onset and largest during exhalation, with pupil dilatation occurring through most of inhalation and the early phase of exhalation, and pupil constriction occurring primarily during the latter part of exhalation. This pattern was consistent across all experimental conditions, demonstrating that it is robust and likely controlled by brainstem circuits. We term this effect the pupillary respiratory-phase response, the fourth known mechanism influencing pupil size.

Brain-body dysconnectivity: deficient autonomic regulation of cortical function in first-episode schizophrenia

BACKGROUND

An accumulating body of evidence indicates that peripheral physiological rhythms help regulate and organize large-scale brain activity. Given that schizophrenia (SZ) is characterized by marked abnormalities in oscillatory cortical activity as well as changes in autonomic function, the present study aimed to identify mechanisms by which central and autonomic nervous system deficits may be related. We evaluated phase-amplitude coupling (PAC) as a physiological mechanism through which autonomic nervous system (ANS) and central nervous system (CNS) activity are integrated and that may be disrupted in SZ.

METHODS

PAC was measured between high-frequency heart rate variability (HF-HRV) as an index of parasympathetic activity and electroencephalography (EEG) oscillations in 36 individuals with first-episode SZ and 38 healthy comparison participants at rest.

RESULTS

HRV-EEG coupling was lower in SZ in the alpha and theta bands, and HRV-EEG coupling uniquely predicted group membership, whereas HRV and EEG power alone did not. HRV-EEG coupling in the alpha band correlated with measures of sustained attention in SZ. Granger causality analyses indicated a stronger heart-to-brain effect than brain-to-heart effect, consistent across groups.

CONCLUSIONS

Lower HRV-EEG coupling provides evidence of deficient autonomic regulation of cortical activity in SZ, suggesting that patterns of dysconnectivity observed in brain networks extend to brain-body interactions. Deficient ANS-CNS integration in SZ may foster a breakdown in the spatiotemporal organization of cortical activity, which may contribute to core cognitive impairments in SZ such as dysregulated attention. These findings encourage pursuit of therapies targeting autonomic function for the treatment of SZ.

Corticolimbic structures activation during preparation and execution of respiratory manoeuvres in voluntary olfactory sampling: An intracranial EEG study

Volitional respiratory manoeuvres such as sniffing and apnoea play a key role in the active olfactory exploration of the environment. Their impairment by neurodegenerative processes could thus impair olfactory abilities with the ensuing impact on quality of life. Functional brain imaging studies have identified brain networks engaged in sniffing and voluntary apnoea, comprising the primary motor and somatosensory cortices, the insula, the anterior cingulate cortex and the amygdala. The temporal organization and the oscillatory activities of these networks are not known. To elucidate these aspects, we recorded intracranial electroencephalograms in six patients during voluntary sniffs and short apnoeas (12 s). The preparation phase of both manoeuvres involved increased alpha and theta activity in the posterior insula, amygdala and temporal regions, with a specific preparatory activity in the parahippocampus for the short apnoeas and the hippocampus for sniff. Subsequently, it narrowed to the superior and median temporal areas, immediately after the manoeuvres. During short apnoeas, a particular dynamic was observed, consisting of a rapid decline in alpha and theta activity followed by a slow recovery and increase. Volitional respiratory manoeuvres involved in olfactory control involve corticolimbic structures in both a preparatory and executive manner. Further studies are needed to determine whether diseases altering deep brain structures can disrupt these mechanisms and if such disruption contributes to the corresponding olfactory deficits. KEY POINTS: Both sniff manoeuvres and short apnoeas are associated with oscillatory activity predominantly in low-frequency bands (alpha and theta). Preparation of sniff manoeuvres and short apnoeas involve activities in low-frequency bands in the posterior insula and temporal regions that extend to amygdala during the execution of both manoeuvres. During short apnoeas, activities in low-frequency bands initially decline before continuously increasing until the apnoeas end.

Effect of comorbid allergic diseases on attention-deficit hyperactivity disorder symptoms and sleep: A cross-sectional study

INTRODUCTION

Recent studies have shown a close relationship between attention-deficit hyperactivity disorder (ADHD) and allergic diseases in children. Regrettably, few studies have investigated the effect of comorbid allergies on ADHD symptoms and sleep, in particular, it is unclear whether comorbid allergic conditions further exacerbate sleep problems in children with ADHD.

OBJECTIVE

To investigate the effect of comorbid allergic on symptoms and sleep in children with ADHD.

METHODS

This was a cross-sectional study, 222 ADHD children (aged 6-14 years) were enrolled in, of whom 93 had allergic diseases and 129 without allergic diseases. Collected all ADHD symptom severity and functional impairment scales, including: Swanson, Nolan and Pelham (SNAP) scale, Integrated Visual and Auditory Continuous Performance Test (IVA-CPT), Conners Parents Symptom questionnaire (PSQ) and Weiss Functional Impairment Rating Scale-Parent Form (WFIRS-P). Every guardian of children diagnosed with ADHD is required to complete the Children's Sleep Habits Questionnaire (CSHQ).

RESULTS

Compared to ADHD children without allergic diseases, we observed significantly higher hyperactivity and impulsivity scores on the SNAP-IV, higher hyperactivity index and impulsivity index on the PSQ, and higher risky activities on the WFIRS-P in ADHD children with comorbid allergic diseases (all p < 0.05). CSHQ total score and sleep disordered breathing were particularly prominent in ADHD children with comorbid allergic diseases (all p < 0.05), and changes in CSHQ correlate with ADHD symptoms and functional impairment. Further analyses revealed that ADHD symptoms and sleep did not worsen with increasing number of comorbid allergic diseases (all p > 0.05). The primary influence on ADHD symptoms and sleep was the type of allergic diseases, where food allergies predominantly influence ADHD symptoms, including attention deficit disorder and hyperactivity disorder (all p < 0.05); allergic rhinitis notably impacts parasomnias, sleep disordered breathing (all p < 0.05); and allergic asthma significantly affects sleep anxiety, daytime sleepiness, and sleep disordered breathing in children with ADHD (all p < 0.05).

CONCLUSION

The presence of comorbid allergic diseases affects both the hyperactivity and impulsivity symptoms of ADHD and sleep disordered breathing, predominantly influenced by the type of the allergic diseases.

Exhaled Breath Analysis: From Laboratory Test to Wearable Sensing

Breath analysis and monitoring have emerged as pivotal components in both clinical research and daily health management, particularly in addressing the global health challenges posed by respiratory and metabolic disorders. The advancement of breath analysis strategies necessitates a multidisciplinary approach, seamlessly integrating expertise from medicine, biology, engineering, and materials science. Recent innovations in laboratory methodologies and wearable sensing technologies have ushered in an era of precise, real-time, and in situ breath analysis and monitoring. This comprehensive review elucidates the physical and chemical aspects of breath analysis, encompassing respiratory parameters and both volatile and non-volatile constituents. It emphasizes their physiological and clinical significance, while also exploring cutting-edge laboratory testing techniques and state-of-the-art wearable devices. Furthermore, the review delves into the application of sophisticated data processing technologies in the burgeoning field of breathomics and examines the potential of breath control in human-machine interaction paradigms. Additionally, it provides insights into the challenges of translating innovative laboratory and wearable concepts into mainstream clinical and daily practice. Continued innovation and interdisciplinary collaboration will drive progress in breath analysis, potentially revolutionizing personalized medicine through entirely non-invasive breath methodology.

Common threads: Altered interoceptive processes across affective and anxiety disorders

There is growing attention towards atypical brain-body interactions and interoceptive processes and their potential role in psychiatric conditions, including affective and anxiety disorders. This paper aims to synthesize recent developments in this field. We present emerging explanatory models and focus on brain-body coupling and modulations of the underlying neurocircuitry that support the concept of a continuum of affective disorders. Grounded in theoretical frameworks like peripheral theories of emotion and predictive processing, we propose that altered interoceptive processes might represent transdiagnostic mechanisms that confer common vulnerability traits across multiple disorders. A deeper understanding of the interplay between bodily states and neural processing is essential for a holistic conceptualization of mental disorders.

Breathing Modulates Network Activity in Frontal Brain Regions during Anxiety

Anxiety elicits various physiological responses, including changes in the respiratory rate and neuronal activity within specific brain regions such as the medial prefrontal cortex (mPFC). Previous research suggests that the olfactory bulb (OB) modulates the mPFC through respiration-coupled oscillations (RCOs), which have been linked to fear-related freezing behavior. Nevertheless, the impact of breathing on frontal brain networks during other negative emotional responses, such as anxiety-related states characterized by higher breathing rates, remains unclear. To address this, we subjected rats to the elevated plus maze (EPM) paradigm while simultaneously recording respiration and local field potentials in the OB and mPFC. Our findings demonstrate distinct respiratory patterns during EPM exploration: slower breathing frequencies prevailed in the closed arms, whereas faster frequencies were observed in the open arms, independent of locomotor activity, indicating that anxiety-like states are associated with increased respiratory rates. Additionally, we identified RCOs at different frequencies, mirroring the bimodal distribution of respiratory frequencies. RCOs exhibited higher power during open-arm exploration, when they showed greater coherence with breathing at faster frequencies. Furthermore, we confirmed that nasal respiration drives RCOs in frontal brain regions and found a stronger effect during faster breathing. Interestingly, we observed that the frequency of prefrontal gamma oscillations modulated by respiration increased with breathing frequency. Overall, our study provides evidence for a significant influence of breathing on prefrontal cortex networks during anxious states, shedding light on the complex interplay between respiratory physiology and emotional processing.

Brain-scale theta band functional connectome as signature of slow breathing and breath-hold phases

The study reported herein attempts to understand the neural mechanisms engaged in the conscious control of breathing and breath-hold. The variations in the electroencephalogram (EEG) based functional connectivity (FC) of the human brain have been investigated during attentive breathing at 2 cycles per minute (cpm). The study presents its novelty through three main aspects. First, it explores the complex breathing circuitry beyond the brain stem, specifically examining how higher brain regions interact with respiratory cycles. Second, unlike previous studies that treated respiratory phases as a singular phenomenon, this research analyses inhalation, exhalation, and breath-holds separately, providing a deeper understanding of their individual dynamics and FC in the brain. Finally, the breathing protocol is designed to include inhale-hold and exhale-hold sessions alongside symmetric breathing, allowing for testing on healthy subjects rather than specialized cohorts, which were used in earlier studies. An experimental protocol involving equal durations of inhale, inhale-hold, exhale, and exhale-hold conditions, synchronized to a visual metronome, was designed and administered to 20 healthy subjects (9 females and 11 males, age: 32.0 ± 9.5 years (mean ± SD)). EEG data were collected during these sessions using the 64-channel eego™ mylab system from ANT Neuro. Further, FC was estimated for all possible pairs of EEG time series data, for 7 EEG bands. Feature selection using a genetic algorithm (GA) was performed to identify a subset of functional connections that would best distinguish the inhale, inhale-hold, exhale, and exhale-hold phases using a random committee classifier. The best accuracy of 95.056% was obtained when 403 theta-band functional connections were fed as input to the classifier, highlighting the efficacy of the theta-band functional connectome in distinguishing these phases of the respiratory cycle. This functional network was further characterized using graph measures, and observations illustrated a statistically significant difference in the efficiency of information exchange through the network during different respiratory phases.

Body as First Teacher: The Role of Rhythmic Visceral Dynamics in Early Cognitive Development

Embodied cognition-the idea that mental states and processes should be understood in relation to one's bodily constitution and interactions with the world-remains a controversial topic within cognitive science. Recently, however, increasing interest in predictive processing theories among proponents and critics of embodiment alike has raised hopes of a reconciliation. This article sets out to appraise the unificatory potential of predictive processing, focusing in particular on embodied formulations of active inference. Our analysis suggests that most active-inference accounts invoke weak, potentially trivial conceptions of embodiment; those making stronger claims do so independently of the theoretical commitments of the active-inference framework. We argue that a more compelling version of embodied active inference can be motivated by adopting a diachronic perspective on the way rhythmic physiological activity shapes neural development in utero. According to this visceral afferent training hypothesis, early-emerging physiological processes are essential not only for supporting the biophysical development of neural structures but also for configuring the cognitive architecture those structures entail. Focusing in particular on the cardiovascular system, we propose three candidate mechanisms through which visceral afferent training might operate: (a) activity-dependent neuronal development, (b) periodic signal modeling, and (c) oscillatory network coordination.

Interoceptive Mechanisms and Emotional Processing

Interoception, the sensing of internal bodily signals, is intricately linked with the experience of emotions. Various theoretical models of emotion incorporate aspects of interoception as a fundamental component alongside higher-order processes such as the appraisal of internal signals guided by external context. Interoception can be delineated into different dimensions, which include the nature of afferent signals, the accuracy with which they can be sensed, their neural processing, and the higher-order interpretation of these signals. This review methodically evaluates these interoceptive dimensions through empirical research to illustrate their role in shaping emotions. Clinical and neurodevelopmental conditions characterized by altered emotional profiles, such as anxiety, depression, schizophrenia, posttraumatic stress disorder, emotionally unstable personality disorder, and autism, exhibit distinct changes in interoception. Various therapeutic approaches, including behavioral, pharmacological, and psychological strategies, may be efficacious for treating conditions associated with emotional alterations by targeting interoceptive mechanisms.

Breathing orchestrates synchronization of sleep oscillations in the human hippocampus

Nested sleep oscillations, emerging from asynchronous states in coordinated bursts, are critical for memory consolidation. Whether these bursts emerge intrinsically or from an underlying rhythm is unknown. Here, we show a previously undescribed respiratory-driven oscillation in the human hippocampus that couples with cardinal sleep oscillations. Further, breathing promotes nesting of ripples in slow oscillations, together suggesting that respiration acts as an intrinsic rhythm to coordinate synchronization of sleep oscillations, providing a unique framework to characterize sleep-related respiratory and memory processes.

Communication subspace dynamics of the canonical olfactory pathway

Understanding how different brain areas communicate is crucial for elucidating the mechanisms underlying cognition. A possible way for neural populations to interact is through a communication subspace, a specific region in the state-space enabling the transmission of behaviorally relevant spiking patterns. In the olfactory system, it remains unclear if different populations employ such a mechanism. Our study reveals that neuronal ensembles in the main olfactory pathway (olfactory bulb to olfactory cortex) interact through a communication subspace, which is driven by nasal respiration and allows feedforward and feedback transmission to occur segregated along the sniffing cycle. Moreover, our results demonstrate that subspace communication depends causally on the activity of both areas, is hindered during anesthesia, and transmits a low-dimensional representation of odor.

What can the psychoneuroimmunology of yoga teach us about depression's psychopathology?

Depression, the most prevailing mental health condition, remains untreated in over 30% of patients. This cluster presents with sub-clinical inflammation. Investigations trialling anti-inflammatory medications had mixed results. The lack of results may result from inflammation's complexity and targeting only a few of depression's abnormal pathways. Mind-body therapies' biological and neuro-imaging studies offer valuable insights into depression psychopathology. Interestingly, mind-body therapies, like yoga, reverse the aberrant pathways in depression. These aberrant pathways include decreased cognitive function, interoception, neuroplasticity, salience and default mode networks connectivity, parasympathetic tone, increased hypothalamic-pituitary-adrenal (HPA) axis activity, and metabolic hyper/hypofunction. Abundant evidence found yogic techniques improving self-reported depressive symptoms across various populations. Yoga may be more effective in treating depression in conjunction with pharmacological and cognitive therapies. Yoga's psychoneuroimmunology teaches us that reducing allostatic load is crucial in improving depressive symptoms. Mind-body therapies promote parasympathetic tone, downregulate the HPA axis, reduce inflammation and boost immunity. The reduced inflammation promotes neuroplasticity and, subsequently, neurogenesis. Improving interoception resolves the metabolic needs prediction error and restores homeostasis. Additionally, by improving functional connectivity within the salience network, they restore the dynamic switching between the default mode and central executive networks, reducing rumination and mind-wandering. Future investigations should engineer therapies targeting the mechanisms mentioned above. The creation of multi-disciplinary health teams offering a combination of pharmacological, gene, neurofeedback, behavioural, mind-body and psychological therapies may treat treatment-resistant depression.

Auditory mismatch negativity is larger during exhalation than inhalation

BACKGROUND

Previous research has shown that internal signals from the body can modulate the processing of external stimuli. This study investigated whether respiratory phases influence auditory deviance detection by recording mismatch negativity (MMN) responses of event-related brain potentials.

METHODS

By reanalyzing the data from a previous study examining the effect of cardiac phases on MMN (Li et al, 2024), we calculated the amplitude of MMN elicited by intensity-deviant stimuli separately for inhalation and exhalation phases in the participants (N = 37).

RESULTS

Results showed that the MMN amplitude was significantly larger during exhalation than inhalation. One possible explanation for this amplitude difference is a greater focus on internal bodily processes during exhalation than inhalation.

CONCLUSION

This study provides further evidence that respiratory phases influence the auditory processing of external events.

Restoring brain connectivity by phrenic nerve stimulation in sedated and mechanically ventilated patients

BACKGROUND

In critically ill patients, deep sedation and mechanical ventilation suppress the brain-diaphragm-lung axis and are associated with cognitive issues in survivors.

METHODS

This exploratory crossover design study investigates whether phrenic nerve stimulation can enhance brain activity and connectivity in six deeply sedated, mechanically ventilated patients with acute respiratory distress syndrome.

RESULTS

Our findings indicate that adding phrenic stimulation on top of invasive mechanical ventilation in deeply sedated, critically ill, moderate acute respiratory distress syndrome patients increases cortical activity, connectivity, and synchronization in the frontal-temporal-parietal cortices.

CONCLUSIONS

Adding phrenic stimulation on top of invasive mechanical ventilation in deeply sedated, critically ill, moderate acute respiratory distress syndrome patients increases cortical activity, connectivity, and synchronization. The observed changes resemble those during diaphragmatic breathing in awake humans. These results suggest that phrenic nerve stimulation has the potential to restore the brain-diaphragm-lung crosstalk when it has been shut down or impaired by mechanical ventilation and sedation. Further research should evaluate the clinical significance of these results.

Discriminating Parkinson's disease patients from healthy controls using nasal respiratory airflow

BACKGROUND

Breathing patterns may inform on health. We note that the sites of earliest brain damage in Parkinson's disease (PD) house the neural pace-makers of respiration. We therefore hypothesized that ongoing long-term temporal dynamics of respiration may be altered in PD.

METHODS

We applied a wearable device that precisely logs nasal airflow over time in 28 PD patients (mostly H&Y stage-II) and 33 matched healthy controls. Each participant wore the device for 24 h of otherwise routine daily living.

RESULTS

We observe significantly altered temporal patterns of nasal airflow in PD, where inhalations are longer and less variable than in matched controls (mean PD = -1.22 ± 1.9 (combined respiratory features score), Control = 1.04 ± 2.16, Wilcoxon rank-sum test, z = -4.1, effect size Cliff's δ = -0.61, 95% confidence interval = -0.79 - (-0.34), P = 4.3 × 10-5). The extent of alteration is such that using only 30 min of recording we detect PD at 87% accuracy (AUC = 0.85, 79% sensitivity (22 of 28), 94% specificity (31 of 33), z = 5.7, p = 3.5 × 10-9), and also predict disease severity (correlation with UPDRS-Total score: r = 0.49; P = 0.008).

CONCLUSIONS

We conclude that breathing patterns are altered by H&Y stage-II in the disease cascade, and our methods may be further refined in the future to provide an indication with diagnostic and prognostic value.

Aging, not Parkinson's disease, decreases a recalibration of body ownership caused by vision-respiratory interaction

Introduction

Recalibration of body ownership perception occurs through an integration among multiple modalities. A recent study has shown that respiratory rhythm also causes the recalibration of ownership perception. However, the risk factors influencing the recalibration of ownership perception caused by vision-respiratory interaction remain unclear. In this study, focusing on aging and Parkinson's disease (PD), we examined the effects of those risk factors on the recalibration.

Methods

By applying the rubber hand illusion (RHI), which temporarily alters ownership perception, and using a device that synchronizes the respiratory rhythm with the movement of a mannequin hand, we measured a change in ownership perception in RHI training by vision-respiratory interaction. The changed ownership was compared among the elderly healthy, PD, and young healthy groups.

Results

The results showed no difference in the changed ownership between the elderly healthy and PD groups, while the two groups decreased the change in the ownership perception compared to the young healthy group.

Discussion

The finding suggests that aging, not PD, related to the recalibration of ownership perception by vision-respiratory interaction. An anomaly in body perception due to aging may be associated with a mechanism in which respiratory rhythm affects the adaptation of body representations.

Beyond anosmia: olfactory dysfunction as a common denominator in neurodegenerative and neurodevelopmental disorders

Olfactory dysfunction has emerged as a hallmark feature shared among several neurological conditions, including both neurodevelopmental and neurodegenerative disorders. While diseases of both categories have been extensively studied for decades, their association with olfaction has only recently gained attention. Olfactory deficits often manifest already during prodromal stages of these diseases, yet it remains unclear whether common pathophysiological changes along olfactory pathways cause such impairments. Here we probe into the intricate relationship between olfactory dysfunction and neurodegenerative and neurodevelopmental disorders, shedding light on their commonalities and underlying mechanisms. We begin by providing a brief overview of the olfactory circuit and its connections to higher-associated brain areas. Additionally, we discuss olfactory deficits in these disorders, focusing on potential common mechanisms that may contribute to olfactory dysfunction across both types of disorders. We further debate whether olfactory deficits contribute to the disease propagation or are simply an epiphenomenon. We conclude by emphasizing the significance of olfactory function as a potential pre-clinical diagnostic tool to identify individuals with neurological disorders that offers the opportunity for preventive intervention before other symptoms manifest.

Threshold-dependent association between non-rapid eye movement obstructive sleep apnea and interictal epileptiform discharges: A hospital study

Obstructive sleep apnea frequently coexists with epilepsy, potentially influencing its pathophysiology. However, the effect of obstructive sleep apnea severity on interictal epileptiform discharges is not well understood. To explore this, we studied 108 Asian patients with epilepsy who underwent single-night polysomnography. We utilized generalized linear models, adjusting for age, sex, epilepsy type (focal versus generalized), antiepileptic medication use and disease duration, to analyse the relationship between obstructive sleep apnea severity, as measured by the apnea-hypopnea index, and interictal epileptiform discharge frequency during non-rapid eye movement and rapid eye movement sleep. Our analysis revealed that severe obstructive sleep apnea (apnea-hypopnea index ≥ 30) was associated with a higher frequency of interictal epileptiform discharges during non-rapid eye movement sleep (p = 0.04), but no such association was observed during rapid eye movement sleep. Additionally, the frequency of interictal epileptiform discharges in non-rapid eye movement sleep was positively correlated with the wake time between sleep onset and offset (p = 0.03). Further studies are warranted to validate our findings across diverse ethnicities, and over multiple nights of sleep and interictal epileptiform discharge recordings.

Nasal obstruction during development leads to defective synapse elimination, hypersynchrony, and impaired cerebellar function

Nasal respiratory disorders are linked to craniofacial anomalies and systemic dysfunctions. However, the implications of nasal respiratory disorders on brain development and their subsequent impact on brain functionalization remain largely unknown. Here, we describe that nasal obstruction from postnatal developmental stages in mice precipitates deficits in cerebellum-associated behaviors and compromised refinement and maturation of neural circuits in the cerebellum. We show that mice with nasal obstruction during developmental phases exhibit marked impairments in motor function and exhibit increased immobility time in forced swimming test. Additionally, we identified critical periods during which nasal respiration is essential for optimizing motor function and preserving mental health. Our study also reveals that nasal obstruction in mice disrupts the typical developmental process of synapse elimination in the cerebellum and hinders the normal transition of activity patterns in cerebellar Purkinje cell populations during development. Through comparing activity patterns in mouse models subjected to nasal obstruction at various stages, we suggest that the maturation of specific activity pattern among Purkinje cell populations is fundamental to the functional integrity of the cerebellum. Our findings highlight the indispensable role of adequate nasal respiration during development for the establishment and functional integrity of neural circuits, thereby significantly affecting brain function.

Humans without a sense of smell breathe differently

Olfaction may play a restricted role in human behavior, yet paradoxically, its absence in anosmia is associated with diverse deleterious outcomes, culminating in reduced life expectancy. The mammalian nose serves two purposes: olfaction and breathing. Because respiratory patterns are impacted by odors, we hypothesized that nasal respiratory airflow may be altered in anosmia. We apply a wearable device that precisely logs nasal airflow for 24-hour-long sessions in participants with isolated congenital anosmia and controls. We observe significantly altered patterns of respiratory nasal airflow in anosmia in wake and in sleep. These differences allow classification of anosmia at 83% accuracy using the respiratory trace alone. Patterns of respiratory airflow have pronounced impact on health, emotion and cognition. We therefore suggest that a portion of the deleterious outcomes associated with anosmia may be attributed to altered patterns of respiratory nasal airflow rather than a direct result of lost odor perception per se.

The timing of sleep spindles is modulated by the respiratory cycle in humans

OBJECTIVE

Coupling of sleep spindles with cortical slow waves and hippocampus sharp-waves ripples is crucial for sleep-related memory consolidation. Recent literature evidenced that nasal respiration modulates neural activity in large-scale brain networks. In rodents, this respiratory drive strongly varies according to vigilance states. Whether sleep oscillations are also respiration-modulated in humans remains open. In this work, we investigated the influence of breathing on sleep spindles during non-rapid-eye-movement sleep in humans.

METHODS

Full night polysomnography of twenty healthy participants were analysed. Spindles and slow waves were automatically detected during N2 and N3 stages. Spindle-related sigma power as well as spindle and slow wave events were analysed according to the respiratory phase.

RESULTS

We found a significant coupling between both slow and fast spindles and the respiration cycle, with enhanced sigma activity and occurrence probability of spindles during the middle part of the expiration phase. A different coupling was observed for slow waves negative peaks which were rather distributed around the two respiration phase transitions.

CONCLUSION

Our findings suggest that breathing cycle influences the dynamics of brain activity during non-rapid-eye-movement sleep.

SIGNIFICANCE

This coupling may enable sleep spindles to synchronize with other sleep oscillations and facilitate information transfer between distributed brain networks.

Single-neuron representations of odours in the human brain

Olfaction is a fundamental sensory modality that guides animal and human behaviour1,2. However, the underlying neural processes of human olfaction are still poorly understood at the fundamental-that is, the single-neuron-level. Here we report recordings of single-neuron activity in the piriform cortex and medial temporal lobe in awake humans performing an odour rating and identification task. We identified odour-modulated neurons within the piriform cortex, amygdala, entorhinal cortex and hippocampus. In each of these regions, neuronal firing accurately encodes odour identity. Notably, repeated odour presentations reduce response firing rates, demonstrating central repetition suppression and habituation. Different medial temporal lobe regions have distinct roles in odour processing, with amygdala neurons encoding subjective odour valence, and hippocampal neurons predicting behavioural odour identification performance. Whereas piriform neurons preferably encode chemical odour identity, hippocampal activity reflects subjective odour perception. Critically, we identify that piriform cortex neurons reliably encode odour-related images, supporting a multimodal role of the human piriform cortex. We also observe marked cross-modal coding of both odours and images, especially in the amygdala and piriform cortex. Moreover, we identify neurons that respond to semantically coherent odour and image information, demonstrating conceptual coding schemes in olfaction. Our results bridge the long-standing gap between animal models and non-invasive human studies and advance our understanding of odour processing in the human brain by identifying neuronal odour-coding principles, regional functional differences and cross-modal integration.

Using a Biofeedback-Based Mindfulness Practice System to Enhance Mindfulness and Alleviate Anxiety in College Students: A Randomized Controlled Trial

Objective: College students experience intense anxiety, for which biofeedback mindfulness techniques show effectiveness in relief. However, typical biofeedback products often lead to user fatigue and boredom because of a single or fixed feedback and lack of focus on mindfulness enhancement. Materials and Methods: In this research, we developed Mindjourney, a VR-based respiratory feedback mindfulness system, designed to enhance mindfulness and alleviate anxiety through continuous/noncontinuous feedback and nonjudgmental reward/punishment for self-perception and attention management. A randomized controlled trial involved 72 college students, split equally into short-term (n = 34, age: 23.11 ± 1.729) and 4-week long-term (n = 38, age: 24.12 ± 1.408) groups, with equal randomization for intervention and control groups. Pre/postintervention tests were measured by using Trait Anxiety Inventory (TAI) and Five Facet Mindfulness Questionnaire (FFMQ) for long-term groups and Galvanic Skin Response and State Anxiety Inventory (SAI) for short-term groups. Results: Results showed that the long-term intervention group showed a significant increase in mindfulness (P = 0.001 for FFMQ total score). Furthermore, observe and act with awareness subscales showed significant increase after intervention (P = 0.034 for observe, P < 0.001 for act with awareness) compared with the control group. Both intervention groups demonstrated a significant decrease in anxiety levels compared with the control groups (P = 0.049 for SAI, P = 0.01 for TAI). Moreover, participants expressed high interest in this biofeedback mindfulness system and willingness for long-term usage. Conclusion: The proposed biofeedback mindfulness practice system could potentially facilitate mindfulness practice and serve as a convenient tool for anxiety relief in campus college students.

Olfactory bulb stimulation mitigates Alzheimer's-like disease progression

BACKGROUND

Deep brain stimulation (DBS) has demonstrated potential in mitigating Alzheimer's disease (AD). However, the invasive nature of DBS presents challenges for its application. The olfactory bulb (OB), showing early AD-related changes and extensive connections with memory regions, offers an attractive entry point for intervention, potentially restoring normal activity in deteriorating memory circuits.

AIMS

Our study examined the impact of electrically stimulating the OB on working memory as well as pathological and electrophysiological alterations in the OB, medial prefrontal cortex, hippocampus, and entorhinal cortex in amyloid beta (Aβ) AD model rats.

METHODS

Male Wistar rats underwent surgery for electrode implantation in brain regions, inducing Alzheimer's-like disease. Bilateral olfactory bulb (OB) electrical stimulation was performed for 1 hour daily to the OB of stimulation group animals for 18 consecutive days, followed by the evaluations of histological, behavioral, and local field potential signal processing.

RESULTS

OB stimulation counteracted Aβ plaque accumulation and prevented AD-induced working memory impairments. Furthermore, it prompted an increase in power across diverse frequency bands and enhanced functional connectivity, particularly in the gamma band, within the investigated regions during a working memory task.

CONCLUSION

This preclinical investigation highlights the potential of olfactory pathway-based brain stimulation to modulate the activity of deep-seated memory networks for AD treatment. Importantly, the accessibility of this pathway via the nasal cavity lays the groundwork for the development of minimally invasive approaches targeting the olfactory pathway for brain modulation.

Exploratory analysis of spontaneous versus paced breathing on heart rate variability in veterans with combat-related traumatic injury

BACKGROUND

Respiration is a crucial determinant of autonomic balance and heart rate variability (HRV). The comparative effect of spontaneous versus paced breathing on HRV has been almost exclusively explored in healthy adults and never been investigated in an injured military cohort.

OBJECTIVE

To examine the effect of spontaneous versus paced breathing on HRV in veterans with combat-related traumatic injury (CRTI).

DESIGN

Observational cohort study.

SETTING

ArmeD serVices trAuma rehabilitatioN outComE (ADVANCE) study, Stanford Hall, UK.

PARTICIPANTS

The sample consisted of 100 randomly selected participants who sustained CRTI (eg, amputation) during their deployment (Afghanistan 2003-2014) and were recruited into the ongoing ADVANCE prospective cohort study.

INTERVENTION

Not applicable.

MAIN OUTCOME MEASURE

HRV was recorded using a single-lead ECG. HRV data were acquired during a sequential protocol of 5-minute spontaneous breathing followed immediately by 5 minutes of paced breathing (six cycles/minute) among fully rested and supine participants. HRV was reported using time domain (root mean square of successive differences), frequency domain (low frequency and high frequency) and nonlinear (sample entropy) measures. The agreement between HRV during spontaneous versus paced breathing was examined using the Bland-Altman analysis.

RESULTS

The mean age of participants was 36.5 ± 4.6 years. Resting respiratory rate was significantly higher with spontaneous versus paced breathing (13.4 ± 3.4 vs. 7.6 ± 2.0 breaths/minute; p < .001), respectively. Resting mean heart rate and root mean square of successive differences were significantly higher with paced breathing than spontaneous breathing (p < .001). Paced breathing significantly increased median low frequency power than spontaneous breathing (p < .001). No significant difference was found in the absolute power of high frequency between the two breathing protocols. The Bland-Altman analysis revealed poor agreement between HRV values during spontaneous and paced breathing conditions with wide limits of agreement.

CONCLUSION

Slow-paced breathing leads to higher HRV than spontaneous breathing and could overestimate resting "natural-state" HRV.

Interoceptive signals shape the earliest markers and neural pathway to awareness at the visual threshold

Variations in interoceptive signals from the baroreceptors (BRs) across the cardiac and respiratory cycle can modulate cortical excitability and so affect awareness. It remains debated at what stages of processing they affect awareness-related event-related potentials (ERPs) in different sensory modalities. We investigated the influence of the cardiac (systole/diastole) and the respiratory (inhalation/exhalation) phase on awareness-related ERPs. Subjects discriminated visual threshold stimuli while their electroencephalogram, electrocardiogram, and respiration were simultaneously recorded. We compared ERPs and their intracranial generators for stimuli classified correctly with and without awareness as a function of the cardiac and respiratory phase. Cyclic variations of interoceptive signals from the BRs modulated both the earliest electrophysiological markers and the trajectory of brain activity when subjects became aware of the stimuli: an early sensory component (P1) was the earliest marker of awareness for low (diastole/inhalation) and a perceptual component (visual awareness negativity) for high (systole/exhalation) BR activity, indicating that BR signals interfere with the sensory processing of the visual input. Likewise, activity spread from the primary visceral cortex (posterior insula) to posterior parietal cortices during high and from associative interoceptive centers (anterior insula) to the prefrontal cortex during low BR activity. Consciousness is thereby resolved in cognitive/associative regions when BR is low and in perceptual centers when it is high. Our results suggest that cyclic fluctuations of BR signaling affect both the earliest markers of awareness and the brain processes underlying conscious awareness.

The International Performance, Resilience and Efficiency Program Protocol for the Application of HRV Biofeedback in Applied Law Enforcement Settings

Law enforcement officers are routinely exposed to high-threat encounters that elicit physiological stress responses that impact health, performance, and safety. Therefore, self-regulation using evidence-based approaches is a priority in police research and practice. This paper describes a five-module heart rate variability biofeedback (HRVB) protocol that is part of a larger resilience program (the International Performance Resilience and Efficiency Program - iPREP) established in 2014. Supported by 10 years of user-informed research and development, our methods are tailored to address occupational stressors and the practical realities of training and resource availability in operational settings. Building on existing clinical methods that comprise five to six weekly sessions and up to 40-min of daily practice, our iPREP HRVB protocol is typically delivered in a condensed format across 2-3 days and is seamlessly integrated with reality-based training scenarios commonly employed in policing. By combining best practices in clinical HRVB with police-specific pedagogical frameworks, officers receive accelerated and job-relevant training to adaptively modulate autonomic responses to acute and chronic stress. Efficacy of the iPREP HRVB protocol is supported by several research studies of various methodological designs (i.e., randomized control trial, longitudinal cohort) that demonstrate immediate and sustained improvements in police performance and physiological health outcomes. We conclude with a critical appraisal of the available empirical evidence contrasting common and emerging breathing techniques proposed for use in operational policing contexts. The critical appraisal guide is intended to serve as a resource for law enforcement agencies, governing bodies, and operators when choosing appropriate and effective self-regulation training approaches.

From nasal respiration to brain dynamic

While breathing is a vital, involuntary physiological function, the mode of respiration, particularly nasal breathing, exerts a profound influence on brain activity and cognitive processes. This review synthesizes existing research on the interactions between nasal respiration and the entrainment of oscillations across brain regions involved in cognition. The rhythmic activation of olfactory sensory neurons during nasal respiration is linked to oscillations in widespread brain regions, including the prefrontal cortex, entorhinal cortex, hippocampus, amygdala, and parietal cortex, as well as the piriform cortex. The phase-locking of neural oscillations to the respiratory cycle, through nasal breathing, enhances brain inter-regional communication and is associated with cognitive abilities like memory. Understanding the nasal breathing impact on brain networks offers opportunities to explore novel methods for targeting the olfactory pathway as a means to enhance emotional and cognitive functions.

Dynamic mechanisms that couple the brain and breathing to the external environment

Brain and breathing activities are closely related. However, the exact neurophysiological mechanisms that couple the brain and breathing to stimuli in the external environment are not yet agreed upon. Our data support that synchronization and dynamic attunement are two key mechanisms that couple local brain activity and breathing to external periodic stimuli. First, we review the existing literature, which provides strong evidence for the synchronization of brain and breathing in terms of coherence, cross-frequency coupling and phase-based entrainment. Second, using EEG and breathing data, we show that both the lungs and localized brain activity at the Cz channel attune the temporal structure of their power spectra to the periodic structure of external auditory inputs. We highlight the role of dynamic attunement in playing a key role in coordinating the tripartite temporal alignment of localized brain activity, breathing and input dynamics across longer timescales like minutes. Overall, this perspective sheds light on potential mechanisms of brain-breathing coupling and its alignment to stimuli in the external environment.

Breathwork-induced psychedelic experiences modulate neural dynamics

Breathwork is an understudied school of practices involving intentional respiratory modulation to induce an altered state of consciousness (ASC). We simultaneously investigate the phenomenological and neural dynamics of breathwork by combining Temporal Experience Tracing, a quantitative methodology that preserves the temporal dynamics of subjective experience, with low-density portable EEG devices. Fourteen novice participants completed a course of up to 28 breathwork sessions-of 20, 40, or 60 min-in 28 days, yielding a neurophenomenological dataset of 301 breathwork sessions. Using hypothesis-driven and data-driven approaches, we found that "psychedelic-like" subjective experiences were associated with increased neural Lempel-Ziv complexity during breathwork. Exploratory analyses showed that the aperiodic exponent of the power spectral density-but not oscillatory alpha power-yielded similar neurophenomenological associations. Non-linear neural features, like complexity and the aperiodic exponent, neurally map both a multidimensional data-driven composite of positive experiences, and hypothesis-driven aspects of psychedelic-like experience states such as high bliss.

Wireless monitoring of respiration with EEG reveals relationships between respiration, behavior, and brain activity in freely moving mice

Active sampling in the olfactory domain is a fundamental aspect of mouse behavior, and there is increasing evidence that respiration-entrained neural activity outside of the olfactory system sets an important global brain rhythm. It is therefore crucial to accurately measure breathing during natural behaviors. We develop a new approach to do this in freely moving animals, by implanting a telemetry-based pressure sensor into the right jugular vein, which allows for wireless monitoring of thoracic pressure. After verifying this technique against standard head-fixed respiration measurements, we combined it with EEG and EMG recording and used evolving partial coherence analysis to investigate the relationship between respiration and brain activity across a range of experiments in which the mice could move freely. During voluntary exploration of odors and objects, we found that the association between respiration and cortical activity in the delta and theta frequency range decreased, whereas the association between respiration and cortical activity in the alpha range increased. During sleep, however, the presentation of an odor was able to cause a transient increase in sniffing without changing dominant sleep rhythms (delta and theta) in the cortex. Our data align with the emerging idea that the respiration rhythm could act as a synchronizing scaffold for specific brain rhythms during wakefulness and exploration, but suggest that respiratory changes are less able to impact brain activity during sleep. Combining wireless respiration monitoring with different types of brain recording across a variety of behaviors will further increase our understanding of the important links between active sampling, passive respiration, and neural activity.NEW & NOTEWORTHY Animals can alter their respiration rate to actively sample their environment, and increasing evidence suggests that neurons across the brain align their firing to this changing rhythm. We developed a new approach to measure sniffing in freely moving mice while simultaneously recording brain activity, and uncovered how specific cortical rhythms changed their coherence with respiration rhythm during natural behaviors and across arousal states.

Uncovering Hemispheric Asymmetry and Directed Oscillatory Brain-Heart Interplay in Anxiety Processing: An fMRI Study

Brain-heart interactions (BHI) are critical for generating and processing emotions, including anxiety. Understanding specific neural correlates would be instrumental for greater comprehension and potential therapeutic interventions of anxiety disorders. While prior work has implicated the pontine structure as a central processor in cardiac regulation in anxiety, the distributed nature of anxiety processing across the cortex remains elusive. To address this, we performed a whole-brain-heart analysis using the full frequency directed transfer function to study resting-state spectral differences in BHI between high and low anxiety groups undergoing fMRI scans. Our findings revealed a hemispheric asymmetry in low-frequency interplay (0.05 Hz - 0.15 Hz) characterized by ascending BHI to the left insula and descending BHI from the right insula. Furthermore, we provide evidence supporting the "pacemaker hypothesis", highlighting the pons' function in regulating cardiac activity. Higher frequency interplay (0.2 Hz - 0.4Hz) demonstrate a preference for ascending interactions, particularly towards ventral prefrontal cortical activity in high anxiety groups, suggesting the heart's role in triggering a cognitive response to regulate anxiety. These findings highlight the impact of anxiety on BHI, contributing to a better understanding of its effect on the resting-state fMRI signal, with further implications for potential therapeutic interventions in treating anxiety disorders.

Dissociative Symptoms and Interoceptive Integration

Dissociative symptoms and disorders of dissociation are characterised by disturbances in the experience of the self and the surrounding world, manifesting as a breakdown in the normal integration of consciousness, memory, identity, emotion, and perception. This paper aims to provide insights into dissociative symptoms from the perspective of interoception, the sense of the body's internal physiological state, adopting a transdiagnostic framework.Dissociative symptoms are associated with a blunting of autonomic reactivity and a reduction in interoceptive precision. In addition to the central function of interoception in homeostasis, afferent visceral signals and their neural and mental representation have been shown to shape emotional feeling states, support memory encoding, and contribute to self-representation. Changes in interoceptive processing and disrupted integration of interoceptive signals into wider cognition may contribute to detachment from the body and the world, blunted emotional experience, and altered subjective recall, as experienced by individuals who suffer from dissociation.A better understanding of the role of altered interoceptive integration across the symptom areas of dissociation could thus provide insights into the neurophysiological mechanisms underlying dissociative disorders. As new therapeutic approaches targeting interoceptive processing emerge, recognising the significance of interoceptive mechanisms in dissociation holds potential implications for future treatment targets.

Cardiorespiratory rhythm-contingent trace eyeblink conditioning in elderly adults

Learning outcome is modified by the degree to which the subject responds and pays attention to specific stimuli. Our recent research suggests that presenting stimuli in contingency with a specific phase of the cardiorespiratory rhythm might expedite learning. Specifically, expiration-diastole (EXP-DIA) is beneficial for learning trace eyeblink conditioning (TEBC) compared with inspiration-systole (INS-SYS) in healthy young adults. The aim of this study was to investigate whether the same holds true in healthy elderly adults (n = 50, aged >70 yr). Participants were instructed to watch a silent nature film while TEBC trials were presented at either INS-SYS or EXP-DIA (separate groups). Learned responses were determined as eyeblinks occurring after the tone conditioned stimulus (CS), immediately preceding the air puff unconditioned stimulus (US). Participants were classified as learners if they made at least five conditioned responses (CRs). Brain responses to the stimuli were measured by electroencephalogram (EEG). Memory for the film and awareness of the CS-US contingency were evaluated with a questionnaire. As a result, participants showed robust brain responses to the CS, acquired CRs, and reported awareness of the CS-US relationship to a variable degree. There was no difference between the INS-SYS and EXP-DIA groups in any of the above. However, when only participants who learned were considered, those trained at EXP-DIA (n = 11) made more CRs than those trained at INS-SYS (n = 13). Thus, learned performance could be facilitated in those elderly who learned. However, training at a specific phase of cardiorespiratory rhythm did not increase the proportion of participants who learned.NEW & NOTEWORTHY We trained healthy elderly individuals in trace eyeblink conditioning, either at inspiration-systole or at expiration-diastole. Those who learned exhibited more conditioned responses when trained at expiration-diastole rather than inspiration-systole. However, there was no difference between the experimental groups in the proportion of individuals who learned or did not learn.

State-dependent alteration of respiration in a rat model of Parkinson's disease

Parkinson's disease (PD) is the second most frequent neurodegenerative disorder. Besides major deficits in motor coordination, patients may also display sensory and cognitive impairments, which are often overlooked despite being inherently part of the PD symptomatology. Amongst those symptoms, respiration, a key mechanism involved in the regulation of multiple physiological and neuronal processes, appears to be altered. Importantly, breathing patterns are highly correlated with the animal's behavioral states. This raises the question of the potential impact of behavioral state on respiration deficits in PD. To answer this question, we first characterized the respiratory parameters in a neurotoxin-induced rat model of PD (6-OHDA) across three different vigilance states: sleep, quiet waking and exploration. We noted a significantly higher respiratory frequency in 6-OHDA rats during quiet waking compared to Sham rats. A higher respiratory amplitude was also observed in 6-OHDA rats during both quiet waking and exploration. No effect of the treatment was noted during sleep. Given the relation between respiration and olfaction and the presence of olfactory deficits in PD patients, we then investigated the odor-evoked sniffing response in PD rats, using an odor habituation/cross-habituation paradigm. No substantial differences were observed in olfactory abilities between the two groups, as assessed through sniffing frequency. These results corroborate the hypothesis that respiratory impairments in 6-OHDA rats are vigilance-dependent. Our results also shed light on the importance of considering the behavioral state as an impacting factor when analyzing respiration.

Ictal Central Apnea Is Predictive of Mesial Temporal Seizure Onset: An Intracranial Investigation

OBJECTIVE

Ictal central apnea (ICA) is a semiological sign of focal epilepsy, associated with temporal and frontal lobe seizures. In this study, using qualitative and quantitative approaches, we aimed to assess the localizational value of ICA. We also aimed to compare ICA clinical utility in relation to other seizure semiological features of focal epilepsy.

METHODS

We analyzed seizures in patients with medically refractory focal epilepsy undergoing intracranial stereotactic electroencephalographic (SEEG) evaluations with simultaneous multimodal cardiorespiratory monitoring. A total of 179 seizures in 72 patients with reliable artifact-free respiratory signal were analyzed.

RESULTS

ICA was seen in 55 of 179 (30.7%) seizures. Presence of ICA predicted a mesial temporal seizure onset compared to those without ICA (odds ratio = 3.8, 95% confidence interval = 1.3-11.6, p = 0.01). ICA specificity was 0.82. ICA onset was correlated with increased high-frequency broadband gamma (60-150Hz) activity in specific mesial or basal temporal regions, including amygdala, hippocampus, and fusiform and lingual gyri. Based on our results, ICA has an almost 4-fold greater association with mesial temporal seizure onset zones compared to those without ICA and is highly specific for mesial temporal seizure onset zones. As evidence of symptomatogenic areas, onset-synchronous increase in high gamma activity in mesial or basal temporal structures was seen in early onset ICA, likely representing anatomical substrates for ICA generation.

INTERPRETATION

ICA recognition may help anatomoelectroclinical localization of clinical seizure onset to specific mesial and basal temporal brain regions, and the inclusion of these regions in SEEG evaluations may help accurately pinpoint seizure onset zones for resection. ANN NEUROL 2024;95:998-1008.

Influence of High-frequency Yoga Breathing (Kapalabhati) on States Changes in Gamma Oscillation

Background

Yoga breathing has been shown to enhance neurocognitive function and positive emotions by increasing electrical power in several frequency bands and synchronizing interhemispheric brain waves. The current study examined the immediate impact of practicing Kapalabhati (KBH) on the electrical activity of the brain.

Methods

Thirty-six individuals who met the inclusion and exclusion criteria and ranged in age from 18 to 25 were randomly assigned, 1:1, to the KBH (n = 18) and breath awareness (BAW) (n = 18) groups. Before data collection, both groups received their respective practices for 10 min each day for a total of 15 days. The brain's electrical activities were assessed using 128-channel EEG recording. The electrodes were placed on their scalps according to the international 10-10 system, ensuring optimal coverage of different brain regions. The EEG signals were amplified, digitized, and stored for offline analysis.

Results

The EEG data showed that the practice of KBH significantly increased alpha waves in the frontal and temporal regions. Moreover, gamma waves increased significantly in the frontal, temporal, and occipital regions after the practice of KBH when compared with BAW.

Conclusion

The results suggest the involvement of frontal and temporal regions, which highlights the importance of KBH in enhancing higher-order cognitive processes. These results provide valuable insights and support for the use of KBH as a potential intervention for individuals seeking to enhance their cognitive abilities.

The Influence of Kapalabhati on Working Memory and Phasic Heart Rate Variability

BACKGROUND

Cognitive communication abilities, such as working memory (WM), are vital for accomplishing daily activities and are also important for higher-order processes such as planning and problem-solving. The current study investigates the simultaneous effect of kapalabhati (KBH) on WM and phasic heart rate variability (HRV).

METHODS

Twenty participants who fulfilled the inclusion and exclusion criteria, with an average age of 23.65±3.07 years (mean±SD), were recruited for the study. Prior to data collection, the participants underwent a seven-day orientation to maintain uniformity in KBH practice. EKGs were assessed using a 16-channel polygraph system arranged in a standard limb lead II configuration. WM was assessed using E-Prime version 2.0 (Psychology Software Tools, Sharpsburg, PA, USA).

RESULTS

There was a significant increase in accuracy after the immediate KBH practice in all three conditions of the WM task (i.e., n-back task: 0-back, 1-back, and 2-back). However, there was also an increase in reaction time. Repeated measures ANOVA of HRV measures showed statistically significant changes in mean rhythm-to-rhythm (RR) intervals, heart rate (HR), number of adjacent N-N intervals over 50 milliseconds (NN50), percentage of successive normal sinus RR intervals greater than 50 milliseconds (pNN50 RR), low frequency (LF), and high frequency (HF), with HR, NN50, pNN50, LF, and HF all significant at p<0.001 and the LF/HF ratio significant at the p<0.01 level.

CONCLUSION

The results of the current study suggest that KBH practice can modulate vagal tone or parasympathetic activity and improve WM performance. Furthermore, the parasympathetic shift found in the present study may promote better cardioprotective health and longevity.

Intracortical brain-heart interplay: An EEG model source study of sympathovagal changes

The interplay between cerebral and cardiovascular activity, known as the functional brain-heart interplay (BHI), and its temporal dynamics, have been linked to a plethora of physiological and pathological processes. Various computational models of the brain-heart axis have been proposed to estimate BHI non-invasively by taking advantage of the time resolution offered by electroencephalograph (EEG) signals. However, investigations into the specific intracortical sources responsible for this interplay have been limited, which significantly hampers existing BHI studies. This study proposes an analytical modeling framework for estimating the BHI at the source-brain level. This analysis relies on the low-resolution electromagnetic tomography sources localization from scalp electrophysiological recordings. BHI is then quantified as the functional correlation between the intracortical sources and cardiovascular dynamics. Using this approach, we aimed to evaluate the reliability of BHI estimates derived from source-localized EEG signals as compared with prior findings from neuroimaging methods. The proposed approach is validated using an experimental dataset gathered from 32 healthy individuals who underwent standard sympathovagal elicitation using a cold pressor test. Additional resting state data from 34 healthy individuals has been analysed to assess robustness and reproducibility of the methodology. Experimental results not only confirmed previous findings on activation of brain structures affecting cardiac dynamics (e.g., insula, amygdala, hippocampus, and anterior and mid-cingulate cortices) but also provided insights into the anatomical bases of brain-heart axis. In particular, we show that the bidirectional activity of electrophysiological pathways of functional brain-heart communication increases during cold pressure with respect to resting state, mainly targeting neural oscillations in theδ $$ \delta $$ ,β $$ \beta $$ , andγ $$ \gamma $$ bands. The proposed approach offers new perspectives for the investigation of functional BHI that could also shed light on various pathophysiological conditions.

Olfactory Epithelium Stimulation Using Rhythmic Nasal Air-Puffs Improves the Cognitive Performance of Individuals with Acute Sleep Deprivation

This study aimed to investigate the effects of intranasal air-puffing on cognitive impairments and brain cortical activity following one night of partial sleep deprivation (PSD) in adults. A total of 26 healthy adults underwent the numerical Stroop test (NST) and electroencephalography (EEG) before and after one night of PSD. Following PSD, subjects in the treatment group (n = 13) received nasal air-puffs (5 Hz, 3 min) before beginning the NST and EEG recording. Administration of nasal air-puffs in the treatment group restored the PSD-induced increase in error rate and decrease in reaction time and missing rate in the NST. Intranasal air-puffs recovered the PSD-induced augmentation of delta and theta power and the reduction of beta and gamma power in the EEG, particularly in the frontal lobes. Intranasal air-puffing also almost reversed the PSD-induced decrease in EEG signal complexity. Furthermore, it had a restorative effect on PSD-induced alteration in intra-default mode network functional connectivity in the beta and gamma frequency bands. Rhythmic nasal air-puffing can mitigate acute PSD-induced impairments in cognitive functions. It exerts part of its ameliorating effect by restoring neuronal activity in cortical brain areas involved in cognitive processing.

Scan-associated anxiety (scanxiety): the enigma of emotional breathing oscillations at 0.32 Hz (19 bpm)

MRI-related anxiety in healthy participants is often characterized by a dominant breathing frequency at around 0.32 Hz (19 breaths per minute, bpm) at the beginning but in a few cases also at the end of scanning. Breathing waves at 19 bpm are also observed in patients with anxiety independently of the scanned body part. In patients with medically intractable epilepsy and intracranial electroencephalography (iEEG), spontaneous breathing through the nose varied between 0.24 and 0.37 Hz (~19 bpm). Remarkable is the similarity of the observed breathing rates at around 0.32 Hz during different types of anxiety states (e.g., epilepsy, cancer, claustrophobia) with the preferred breathing frequency of 0.32 Hz (19 bpm), which is predicted by the binary hierarchy model of Klimesch. This elevated breathing frequency most likely reflects an emotional processing state, in which energy demands are minimized due to a harmonic coupling ratio with other brain-body oscillations.

Oscillatory Coupling Between Neural and Cardiac Rhythms

Oscillations serve a critical role in organizing biological systems. In the brain, oscillatory coupling is a fundamental mechanism of communication. The possibility that neural oscillations interact directly with slower physiological rhythms (e.g., heart rate, respiration) is largely unexplored and may have important implications for psychological functioning. Oscillations in heart rate, an aspect of heart rate variability (HRV), show remarkably robust associations with psychological health. Mather and Thayer proposed coupling between high-frequency HRV (HF-HRV) and neural oscillations as a mechanism that partially accounts for such relationships. We tested this hypothesis by measuring phase-amplitude coupling between HF-HRV and neural oscillations in 37 healthy adults at rest. Robust coupling was detected in all frequency bands. Granger causality analyses indicated stronger heart-to-brain than brain-to-heart effects in all frequency bands except gamma. These findings suggest that cardiac rhythms play a causal role in modulating neural oscillations, which may have important implications for mental health.

Phase-locked breathing does not affect episodic visual recognition memory but does shape its corresponding ERPs

Recent studies have indicated that breathing shapes the underlying oscillatory brain activity critical for episodic memory, potentially impacting memory performance. However, the literature has presented conflicting results, with some studies suggesting that nasal inhalation enhances visual memory performance, while others have failed to observe any significant effects. Furthermore, the specific influence of breathing route (nasal vs. mouth) and the precise phase of the respiratory cycle during which stimuli are presented have remained elusive. To address this, we employed a visual recognition memory (VRM) and electroencephalography paradigm in which stimuli presentation was phase-locked to either inhalation or exhalation onset, using a within-subject design where participants performed the memory task while engaging in separate sessions of nose and mouth breathing. We show that neither breathing route nor breathing phase has a significant impact on VRM performance as measured by d-prime, with the data supporting the null hypothesis. However, we did find an effect of breathing phase on response bias, with participants adopting a more conservative decision criterion during exhalation. Moreover, we found that breathing phase during memory encoding shaped the late parietal effect (LPE) amplitude, while the Frontal Negative Component (FN400) and LPE during recognition were less impacted. While our study demonstrates that breathing does not shape VRM performance, it shows that it influences brain activity, reinforcing the importance of further research to elucidate the extent of respiratory influence on perception, cognition, and behavior.

What do brain oscillations tell about the human sense of smell?

Brain activity may manifest itself as oscillations which are repetitive rhythms of neuronal firing. These local field potentials can be measured via intracranial electroencephalography (iEEG). This review focuses on iEEG used to map human brain structures involved in olfaction. After presenting the methodology of the review, a summary of the brain structures involved in olfaction is given, followed by a review of the literature on human olfactory oscillations in different contexts. A single case is provided as an illustration of the olfactory oscillations. Overall, the timing and sequence of oscillations found in the different structures of the olfactory system seem to play an important role for olfactory perception.

Integrative neuro-cardiovascular dynamics in response to test anxiety: A brain-heart axis study

Test anxiety (TA), a recognized form of social anxiety, is the most prominent cause of anxiety among students and, if left unmanaged, can escalate to psychiatric disorders. TA profoundly impacts both central and autonomic nervous systems, presenting as a dual manifestation of cognitive and autonomic components. While limited studies have explored the physiological underpinnings of TA, none have directly investigated the intricate interplay between the CNS and ANS in this context. In this study, we introduce a non-invasive, integrated neuro-cardiovascular approach to comprehensively characterize the physiological responses of 27 healthy subjects subjected to test anxiety induced via a simulated exam scenario. Our experimental findings highlight that an isolated analysis of electroencephalographic and heart rate variability data fails to capture the intricate information provided by a brain-heart axis assessment, which incorporates an analysis of the dynamic interaction between the brain and heart. With respect to resting state, the simulated examination induced a decrease in the neural control onto heartbeat dynamics at all frequencies, while the studying condition induced a decrease in the ascending heart-to-brain interplay at EEG oscillations up to 12Hz. This underscores the significance of adopting a multisystem perspective in understanding the complex and especially functional directional mechanisms underlying test anxiety.

Single neurons in the thalamus and subthalamic nucleus process cardiac and respiratory signals in humans

Visceral signals are constantly processed by our central nervous system, enable homeostatic regulation, and influence perception, emotion, and cognition. While visceral processes at the cortical level have been extensively studied using non-invasive imaging techniques, very few studies have investigated how this information is processed at the single neuron level, both in humans and animals. Subcortical regions, relaying signals from peripheral interoceptors to cortical structures, are particularly understudied and how visceral information is processed in thalamic and subthalamic structures remains largely unknown. Here, we took advantage of intraoperative microelectrode recordings in patients undergoing surgery for deep brain stimulation (DBS) to investigate the activity of single neurons related to cardiac and respiratory functions in three subcortical regions: ventral intermedius nucleus (Vim) and ventral caudalis nucleus (Vc) of the thalamus, and subthalamic nucleus (STN). We report that the activity of a large portion of the recorded neurons (about 70%) was modulated by either the heartbeat, the cardiac inter-beat interval, or the respiration. These cardiac and respiratory response patterns varied largely across neurons both in terms of timing and their kind of modulation. A substantial proportion of these visceral neurons (30%) was responsive to more than one of the tested signals, underlining specialization and integration of cardiac and respiratory signals in STN and thalamic neurons. By extensively describing single unit activity related to cardiorespiratory function in thalamic and subthalamic neurons, our results highlight the major role of these subcortical regions in the processing of visceral signals.

Motor Dysfunctions in Fibromyalgia Patients: The Importance of Breathing

The classification of fibromyalgia (FM) is not always immediate and simple, with the time from the first diagnosis, compared to the onset of symptoms, of a few years. Currently, we do not have instrumental or biochemical tests considered as gold standards; the clinician will make a diagnosis of FM based on the patient's medical history and subjective assessment. The symptoms can involve physical, cognitive and psychological disorders, with the presence of pain of different origins and classifications: nociplastic, nociceptive and neuropathic pain. Among the symptoms highlighted, postural disorders and neuromotor uncoordination emerge, whose functional dysfunctions can increase the mortality and morbidity rate. An alteration of the diaphragm muscle could generate such functional motor problems. Considering that the current literature underestimates the importance of breathing in FM, the article aims to highlight the relationship between motor and diaphragmatic difficulties in the patient, soliciting new points of view for the clinical and therapeutic framework.