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How Do You Feel? Interoception: The Sense of the Physiological Condition of the Body
Abstract
As humans, we perceive feelings from our bodies that relate our state of well-being, our energy and stress levels, our mood and disposition. How do we have these feelings? What neural processes do they represent? Recent functional anatomical work has detailed an afferent neural system in primates and in humans that represents all aspects of the physiological condition of the physical body. This system constitutes a representation of 'the material me', and might provide a foundation for subjective feelings, emotion and self-awareness.
... The bodily self, emotion, and subjective time are fundamentally linked through the processes of interoception and anticipation. Appreciation of this linkage was pioneered by Bud Craig (2002) and has been forwarded by countless other researchers over the last few decades. It was no coincidence that much of the original mapping of these pathways was from the field of pain research, as pain is fundamental to the way that we understand and behave in relationship to the world around us (de C Williams 2023). ...
... This emotional-interoceptive relationship is processed through an interconnected network of brain regions including the insula and anterior cingulate cortexareas crucial for integrating bodily signals with emotional states (Craig 2002(Craig , 2015 Critchley and Patchitt 2024) (see chapters "Insula and Interoceptive Pathways" and "Emotions and Physiological Feelings" in this volume). When individuals experience negative emotions, these same neural circuits show heightened activation, which can prime the brain for enhanced pain perception through altered interoceptive sensitivity. ...
... The primary interoceptive pathway begins with small-diameter (A-delta and C) sensory fibers, which detect thermal, mechanical, and chemical conditions throughout body tissues. These signals are initially processed in lamina I of the spinal cord, then conveyed through a specific thalamic relay to reach the posterior insula, which functions as the primary interoceptive cortex (Craig 2002(Craig , 2003aCraig and Blomqvist 2002). From here, information is progressively processed along a posterior-to-anterior gradient within the insula. ...
This chapter focuses on the interconnectedness of bodily awareness, emotion, and time perception, focusing on the roles of interoception and anticipation, pioneered by A.D. (Bud) Craig and advanced by contemporary research. Pain, a pivotal aspect of human experience, serves as a conduit for understanding our relationship with the world. Anticipation of pain, vital for survival, influences subjective pain experiences and is modulated by factors such as physiological reactivity and contextual cues. Emotional states significantly shape pain perception, with chronic pain conditions and affective disorders characterized by dysregulated pain modulation mechanisms. We discuss a state space model for pain, wherein pain functions as a latent construct shaped by both anticipatory and contemporaneous factors. Understanding these mechanisms is critical for informing clinical interventions aimed at pain management and highlights the intersection of interoception, emotion, and pain.
... My work demonstrated that thermal pain is not just a sensation, but also an emotion, and these two components are not always closely linked. As Bud Craig eloquently stated in 2002 (Craig 2002), my first studyunbeknownst to me at the timewas actually connected to his life's work: the close relationship between bodily sensations of temperature and pain and emotional feelings. I could not articulate this connection as clearly until Bud published his seminal paper in Nature Reviews Neuroscience in 2002 (Craig 2002), as discussed below. ...
... As Bud Craig eloquently stated in 2002 (Craig 2002), my first studyunbeknownst to me at the timewas actually connected to his life's work: the close relationship between bodily sensations of temperature and pain and emotional feelings. I could not articulate this connection as clearly until Bud published his seminal paper in Nature Reviews Neuroscience in 2002 (Craig 2002), as discussed below. ...
... My initial understanding of the insula was a very rudimentary concept of a mysterious island that took care of the gut. My perspective quickly changed when Martin recognized the gravity of Bud's seminal work in interoception (Craig 2002). His exploration into the uncharted regions of the insula provided a road map that I continued to follow over the years. ...
A.D. (Bud) Craig was best known to us colloquially as Bud Craig; his groundbreaking work has advanced our understanding of the neuroanatomical basis of the bodily self, emotion, and subjective time. His research elucidated the intricate pathways of interoception – the brain’s processing of internal body signals – and highlighted the insula’s pivotal role in integrating these signals. Craig’s pioneering insights demonstrated that bodily sensations, such as pain and temperature, are deeply intertwined with emotional experiences and homeostatic needs. By mapping the thalamocortical pathways and emphasizing the insula’s function in predicting future bodily states, he provided a comprehensive framework that connects physiological states to emotional and temporal experiences. This fundamental work has profoundly influenced a new generation of scientists and inspired the current volume. In this book, we have invited researchers influenced by Craig’s theories to explore the neural correlates of emotion, pain, interoception, and time. In this chapter, we present how the editors of this book were directly influenced by Craig’s findings and lay the groundwork for the large collective contribution of the authors of the subsequent chapters that continue to explore this ever-evolving scientific landscape.
... Returning to the concept of interoception-our internal sensory system-allows a deeper understanding of how these seemingly embodied experiences are intimately entangled with the Body Without Organs (BwO). Although interoception conventionally refers to physiological signals such as heart rate, respiration, digestion, pain, and temperature, these signals are never purely objective or isolated (Craig, 2002). Instead, they are continuously filtered and shaped by an interplay of past experiences, emotional states, cognitive biases, and the unstructured, dynamic flows of the BwO. ...
... Investigating the neurological correlates of these micro-movements and affective fluctuations could illuminate how perception and action continuously unfold in a BwO-mediated manner. To this end, new experimental methodologies must be developed-capable of capturing fleeting, distributed, and dynamic physiological signals beyond the scope of traditional behavioral paradigms and neuroimaging techniques (Craig, 2002;Barrett & Simmons, 2015). These approaches may involve high-resolution time-series analyses, hyperscanning of interpersonal affective dynamics, and machine learning techniques tailored for complex embodied data. ...
In this interdisciplinary essay, we reimagine Gilles Deleuze and Félix Guattari’s concept of the _Body without Organs_ (BwO) as a generative framework for understanding embodied cognition, affective flows, and predictive processing across biology, mathematics, and neuroscience. Moving beyond its philosophical origins, the BwO is developed here as a dynamic field of unformed potentiality that cuts across molecular biology, mathematical abstraction (as topological and categorical virtuality), and the neural-affective systems of cognition (as self-organizing predictive agents). We argue that cognition emerges through continuous negotiation with this pre-individual field—a process of sensing, predicting, and becoming shaped by affective micro-events, interoceptive modulations, and relational intensities. Drawing from process philosophy, embodied cognitive science, and dynamical systems theory, we position the BwO as an ontological ground for understanding not just the mind, but the very becoming of bodies, networks, and worlds. This essay proposes a novel conceptual ecology where the embodied brain is not an organized organ, but a fluid interface with the virtual: a topological becoming that reconfigures cognition as improvisation on a field of affective and mathematical possibility. This interdisciplinary framework invites empirical elaboration and theoretical critique from scholars in neuroscience, philosophy, biology, and mathematics.
Keywords: Body Without Organs, Embodied Cognition, Predictive Processing, Affective Neuroscience, Process Philosophy, Philosophical Biology, Self-Organization, Interoception
... It has been widely studied for its benefits in reducing the symptoms of various psychological disorders including anxiety, depression, and stress-related disorders (Hölzel et al., 2011). Interoception, defined as the sensory processing of internal bodily signals, complements mindfulness by providing a deeper understanding of the physiological processes related to emotions and health (Craig, 2002). Together, these practices form a robust framework for developing a heightened state of self-awareness and regulation. ...
... It is a critical component of how individuals perceive and react to emotional states (Craig, 2002). By enhancing one's awareness of physiological signals, interoception contributes significantly to emotional regulation and self-awareness. ...
Recent developments in positive psychology and spiritual practices suggest a nuanced pathway to enhancing psychological well-being through the cultivation of mindfulness, interoception, and balanced dual emotions. This article explores the conceptual progression from mindfulness to interoception, further leading to an understanding of internal values and the strategic balancing of the dual emotions of silence and happiness. Mindfulness, defined as the non-judgmental focus on the present moment. Interoception, or the awareness of internal body sensations, complements mindfulness by enhancing self-regulation. The integration of silence and happiness as dual emotions contributes to mental clarity which is crucial for reducing symptoms of anxiety and depression. Happiness, associated with positive social interactions and compassion, plays a critical role in the promotion of relational well-being. By maintaining a balance between these emotions, individuals may experience enhanced well-being through improved hormonal balance and psychological resilience. Supported by spiritual practices that emphasize egolessness and contentment, this model proposes that mindfulness, interoception, and dual emotion management can synergistically foster a health-promoting environment, both psychologically and physiologically. This research involving development of Heal-thy Life Spiritual Psychology Assessment Scale (HLSPAS) aims to synthesize these elements into a coherent model that contributes to the broader understanding of psychological well-being, drawing from spiritual experience and practice in these areas.
... Interoception was originally defined as the body's sensory system for detecting visceral states (Cameron, 2001;Sherrington, 1906). Over time, this definition has expanded to encompass both the physiological and cognitive mechanisms involved in tracking internal bodily signals (Craig, 2002). These signals, conveyed via specialized afferent pathways, not only support homeostatic regulation (Crucianelli & Ehrsson, 2023;Desmedt et al., 2023), but also contribute to the detection, interpretation, and integration of internal states, facilitating brain-body communication at both conscious and unconscious levels (Khalsa et al., 2018). ...
... The NTS functions as an integrative hub, receiving input from multiple bodily systems and projecting to viscerosensitive regions such as the insular cortex; a key structure for integrating interoceptive information with affective, cognitive, and subjective states (Craig, 2009;Namkung et al., 2017; see Figure 1). The insula connects to the thalamus, hypothalamus, amygdala, and the cingulate, orbitofrontal, and somatosensory cortices, forming part of the allostatic-interoceptive network (AIN) (Chen et al., 2021;Craig, 2002), which plays a central role in internal state regulation and interoceptive processing. ...
A growing body of evidence indicates that perception is shaped not only by external stimuli but also by rhythmic signals originating from the heart, lungs, and stomach. These ongoing internal bodily rhythms can modulate sensory processing, influencing both low-level detection and higher-order functions such as emotion recognition and social decision-making. The first part of this review outlines the physiology of each organ–brain axis and synthesizes current findings on how cardiac, respiratory, and gastric rhythms modulate perceptual experience. Altogether, current findings highlight the role of interoceptive rhythms in shaping moment-to-moment perceptual outcomes. Although these effects can differ based on specific task demands, a pattern emerges in the literature: in certain instances, perception may vary based on the dynamic distribution of signal processing resources between internal bodily states and external environmental stimuli. Acknowledging the limitations of existing experimental paradigms, the second part of this review seeks to build on these empirical findings by proposing strategies to improve the ecological validity and generalizability of interoception-perception research. Our analysis of participant demographics across the reviewed studies highlights the necessity for more diverse demographic representation. We also propose the integration of multimodal physiological recordings and wearable technologies, alongside the creation of more dynamic paradigms that can capture behaviors in real-world contexts. These recommendations are intended to enhance both the representativeness and ecological validity of interoception-perception research. By linking traditional laboratory paradigms with more naturalistic settings, this review and framework may pave the way for a deeper understanding of how interoceptive signals influence perception in everyday life. Last, we briefly explore emerging theoretical models that, when integrated with ecologically relevant designs, could provide a more comprehensive understanding of embodied cognition.
... Interoception, in its broadest sense, is defined as the process of perceiving and evaluating information about the body's internal physiological state. This includes visceral sensations, cardiovascular and gastrointestinal signals, hunger and thirst, and tactile sensations such as pain, pressure, and temperature perception (Craig, 2002;Quadt et al., 2018). In addition, illness states of the body, e.g. ...
... Research has demonstrated that HEPs are modulated by attention, interoceptive awareness and arousal (Coll et al., 2021;Montoya et al., 1993;Petzschner et al., 2019;Schandry & Weitkunat, 1990). Previous research has shown that HEPs were most prominent over frontal and frontocentral electrodes, which has been linked to activity in the insula, the anterior cingulate cortex, the prefrontal cortex and the somatosensory cortices (Craig, 2002;Pollatos et al., 2007). Furthermore, HEPs have been related to heart rate variability (HRV), which is a measure for ANS functioning (Flasbeck et al., 2021;MacKinnon et al., 2013). ...
Interoception, or the perception of internal somatic states, is crucial for signaling the individual to take care of the body when needed. It enables behavioral adaptations to sickness states, which further impact autonomic nervous system (ANS) activity. Whether acute inflammation affects interoceptive processing and how this relates to sickness behavior remains unknown. Therefore, we investigated interoceptive processing in participants undergoing experimental endotoxemia. In neuroimaging research, heartbeat-evoked potentials (HEP) - defined as event-related potentials time-locked to electrocardiogram (ECG) R-waves during electroencephalogram (EEG) recordings - have emerged as a promising metric for cardiac interoceptive processing. We analyzed the effects of intravenous administration of lipopolysaccharide (LPS; 0.4 ng/kg) or placebo, on HEP amplitudes and ANS functioning in healthy, female participants (n=52) during 8 minutes resting-state EEG and ECG recordings before and 2 hours after injections. Our results showed increased cortisol and cytokine levels in the LPS group, along with increased sympathetic and decreased parasympathetic activity 2 hours after injections compared to the placebo group. Placebo-injected participants exhibited lower post injection-baseline differences in HEP amplitudes in an early timeframe (255-455ms), indicating lower HEPs 2 hours after administrations. Moreover, post-injection HEP amplitudes differed between groups, suggesting that while participants in the placebo group showed altered HEP amplitudes after injection, HEPs remained unresponsive to LPS administration. These findings are discussed in the context of predictive processing, expectation violation and attention direction to external and interoceptive cues. Future research should further investigate the role of LPS dose and explore behavioral measures of interoception under experimental inflammation.
... Neuroimaging studies have shown that the insular cortex, a region involved in affective touch (Gordon et al. 2013), is activated during ASMR experiences (Lochte et al. 2018, Sakurai et al. 2023). However, the insular cortex is also known to play a broader role in emotional and interoceptive processing (Craig 2002, Critchley et al. 2004) and is activated in other sensory-emotional phenomena such as misophonia and musical chills (Blood and Zatorre 2001, Kumar et al. 2017, even though these phenomena are less directly related to affective touch. The convergence of insular activity across these different experiences highlights its integrative role in linking sensory and emotional states. ...
... This cross-activation is believed to link exteroceptive sensations with internal bodily sensations, giving rise to ASMR experiences. Individuals who respond to ASMR triggers exhibit heightened interoceptive awareness (Poerio et al. 2022a), which refers to the perception of internal bodily states and is associated with increased autonomic reactivity (Craig 2002). Moreover, tingling sensations are likely tied to activation of Ctactile afferents, specialized nerve fibers that respond to gentle, caress-like touch (Olausson et al. 2002, Morrison et al. 2010). ...
Autonomous sensory meridian response (ASMR) is a sensory–emotional phenomenon characterized by distinct tingling sensations and a sense of relaxation induced by specific auditory and visual stimuli. Although ASMR is recognized as a cross-modal experience, psychological and physiological mechanisms behind ASMR remain only partially understood. Across two experiments, we investigated these mechanisms. Experiment 1 showed that ASMR videos with combined audiovisual content elicited stronger tingling sensations than those with auditory-only content, suggesting an additive effect through sensory processing. In Experiment 2, we measured responses to ASMR and nature videos using finger photoplethysmography (PPG) and found that both types of videos reduced pulse rates compared to rest. Notably, ASMR videos caused a greater reduction in pulse rate than nature videos. These findings are discussed in relation to autonomic nervous system activation, cross-modal interactions, and the social grooming hypothesis, which posits that ASMR may replicate comforting effects of social bonding behaviors, such as grooming.
... Therapeutic IE acclimates individuals to the physiological sensations of anxiety, reduces sensitivity and modulates individual responses to SNS activation [20]. Prolonged and intense IE with coaching to promote mindful observation, acceptance, re-interpretation, and response to the experience of arousal has been shown to improve CBT outcomes [7,[21][22][23]. A typical TBr session includes 45 minutes of HVB, delivering prolonged therapeutic interoceptive exposure, and integrates various techniques to support the subject through the experience in a similar methodology of mindful acceptance to CBT. ...
Music Performance Anxiety, a subset of social anxiety disorder (SAD), can significantly impede the lives of professional voice users (PVUs). This pilot cohort study evaluates the efficacy of Transformational Breath (TBr), a facilitated conscious breathing technique that employs high ventilation breathing, as a therapeutic intervention for anxiety management in PVUs. We recruited PVUs diagnosed with mild to moderate SAD and randomly assigned them to an intervention group (n = 12) that completed three TBr sessions with a certified practitioner, or to a waitlist control group (n = 12). Both groups were assessed using a battery of psychological (Generalised Anxiety Disorder Scale (GAD-7), Patient Health Questionnaire (PHQ-9), Social Phobia Index (SPIN), Kenny’s Music Performance Anxiety Inventory (K-MPAI), Warwick-Edinburgh Mental Well-Being Scale (WEMWBS)) and physiological (blood pressure, heart rate, respiratory rate, oxygen saturations, peak expiratory flow rate) measures on three separate occasions. The outcome measures were evaluated before and after each session in the intervention group. No Group x Time interaction was found for any of the physiological or psychological measures. However, a significant Time main effect was found for K-MPAI (X2(5)=20.157, p = .001) and GAD-7 (X2(5)=12.79, p = .025) within the TBr group. Post hoc Wilcoxon-signed rank tests with Bonferroni correction for multiple comparisons revealed significant differences between K-MPAI scores at time points Post 3 and Pre 3 (z = 3.00, adj. p = .040), Post 3 and Pre 2 (z = 3.27, adj. p = .016) and Post 3 and Pre 1 (z = 2.95, adj. p = .048). No pairwise differences were found for GAD-7. The pattern of results suggests that TBr may be effective in acutely decreasing music performance anxiety.
... This increase in FC during the infusion returned to baseline levels at the delayed time point. The insula has been identified as a multimodal interoceptive integration area, integrating emotional-motivational and somatosensory aspects (Craig, 2002(Craig, , 2009. The augmented FC between the pgACC and the insula, both of which are linked to interoception, may suggest an enhancement in interoceptive capacity. ...
Background
Neuroimaging studies have linked the beneficial effects of subanaesthetic ketamine doses in psychiatric conditions characterized by chronic stress pathology (CSP) to altered functional connectivity (FC) within the pregenual anterior cingulate cortex (pgACC). Previous research indicates a potential role of glutamate concentration in FC changes; however, the precise relationship between glutamate release and increased FC remains unclear. Lamotrigine, a glutamate-release inhibitor, allows deeper exploration of this relationship. Additionally, CSP and treatment efficacy are closely associated with alterations in working memory (WM), necessitating the examination of FC during resting state and WM tasks.
Aims
This study aimed to investigate the acute and sustained effects of altered glutamate transmission induced by ketamine and lamotrigine on pgACC FC during rest and WM.
Methods
In this double-blind, placebo-controlled, randomized, single-dose, parallel-group study, resting-state and task-related functional Magnetic Resonance Imaging (fMRI) data were collected at baseline, during and 24 h after ketamine administration in 75 healthy participants. Participants were randomized to receive ketamine, ketamine with lamotrigine pretreatment or placebo. FC analyses utilized pgACC masks derived from the Julich Brain Atlas.
Results
Ketamine infusion significantly enhanced FC between the pgACC and dorsomedial prefrontal cortex during the WM task, and increased resting-state FC between the pgACC and left insula. These effects were absent following lamotrigine pretreatment.
Conclusions
The findings support the hypothesis that ketamine’s favourable effects, reflected by enhanced FC within key neural networks, may be attributable to glutamate release.
... This study positions integrative silence as a compassionate alternative to cognitively driven, memory-recall-based practices that can unintentionally re-traumatise survivors, particularly within marginalised communities. Grounded in feminist and decolonial frameworks, the study views embodiment as the physiological awareness of the body in a present moment (Barrett et al., 2005;Craig, 2002). Drawing on Barrett's (2017) theory of constructed emotion, the study explores how silence supports affective regulation across a continuum of embodied and interoceptive awareness (Barrett & Simmons, 2015). ...
Background: Research has demonstrated that the verbal disclosure for adult victims of childhood sexual trauma (CST) presents significant challenges and seldom provides comprehensive trauma integration. Limited psychosocial support and specialist trauma care particularly in marginalised communities, can further exacerbate the non-disclosure of CST. Although various intervention models for adult victims of CST exist, the potential of facilitating integrative silence as part of community centred integrative trauma informed care (ITIC), remains under-explored.
Objective: The objective of this article, is to document how facilitating spaces of integrative silence in a therapeutic context, shifts embodied trauma awareness, comprehensive trauma realisation and trauma integration for adult victims of CST from intergenerational marginalised contexts.
Methods: Through participatory action research (PAR), framed in de-colonial feminist community praxis with 13 women aged 21-62, the first author as therapist-researcher facilitated audio-visual recorded semi-structured interviews (n = 13) and integrative trauma informed care (ITIC) follow-up sessions (n = 60) to assess the value of the spoken, unspoken and silence in trauma care. Inductive reflexive thematic analysis and a multistage recursive coding process of verbatim transcriptions, were used to identify embodied trauma awareness before, during, and after periods of silence.
Results: The de-colonial, feminist framing for community centred ITIC enhanced participant-specific embodied awareness, establishing a safe space for self-reflection. Contextual sensitivity and careful attention to the therapeutic environment were paramount. The facilitation of non-verbal expression empowered participants to explore alternatives to normative, essentialist and religious narratives that often stigmatise trauma responses. This approach enabled participants to reclaim a sense of agency, improving self-regulation and self-care.
Conclusion: This study highlights the potential of integrative silence in community based therapeutic contexts. Future research could explore the role of integrative silence in treating various forms of trauma in different cultural and geographic settings and its integration with other therapeutic modalities to enhance culturally sensitive mental health care.
... The drive function D(s i ) returns a value greater than or equal to zero, such as the distance between s i and s * . Here s i is interoception that monitors the internal state of the agent's body (Sherrington, 1906;Craig, 2002) and s * is the set point of the interoception. Homeostatic parameters are not arbitrarily defined, but are fundamental to the viability and functionality of the agent (Keramati and Gutkin, 2014;Man and Damasio, 2019). ...
When regarding the suffering of others, we often experience personal distress and feel compelled to help\footnote{Preprint. Under review.}. Inspired by living systems, we investigate the emergence of prosocial behavior among autonomous agents that are motivated by homeostatic self-regulation. We perform multi-agent reinforcement learning, treating each agent as a vulnerable homeostat charged with maintaining its own well-being. We introduce an empathy-like mechanism to share homeostatic states between agents: an agent can either \emph{observe} their partner's internal state ({\bf cognitive empathy}) or the agent's internal state can be \emph{directly coupled} to that of their partner ({\bf affective empathy}). In three simple multi-agent environments, we show that prosocial behavior arises only under homeostatic coupling - when the distress of a partner can affect one's own well-being. Additionally, we show that empathy can be learned: agents can ``decode" their partner's external emotive states to infer the partner's internal homeostatic states. Assuming some level of physiological similarity, agents reference their own emotion-generation functions to invert the mapping from outward display to internal state. Overall, we demonstrate the emergence of prosocial behavior when homeostatic agents learn to ``read" the emotions of others and then to empathize, or feel as they feel.
... Fatigue and monocyte activation are common features of chronic HIV disease management, particularly in postmenopausal women. Signals of inflammation are detected by afferent vagal pathways to the nucleus tractus solitarius and parabrachial nucleus before being relayed to the basal ganglia and then onto cortical regions involved in interoceptive processing (Goehler et al., 2000;Craig, 2002). While measures of monocyte activation have been linked to fatigue in other inflammatory-immune conditions, our understanding of the mediating role of the central nervous system is limited. ...
Post-menopause is associated with chronic fatigue, inflammation, and aberrant brain connectivity, however there is a dearth of studies comparing these effects as a function of HIV. The current study investigated whether degree centrality of the thalamus mediates the effect of sCD14, a marker of monocyte activation, on fatigue and whether those parameters vary as a function of HIV-status. Resting-state functional connectivity MRI data, blood plasma, and self-report data were collected from 16 HIV + and 25 HIV- post-menopausal women. Analyses tested whether degree centrality of the thalamus, caudate, and right putamen mediated the relationship between sCD14 and fatigue. HIV-serostatus was then tested as a moderator. Compared to HIV-negative, HIV + women had higher levels of sCD14, t(34) = -3.85, p <.001, and lower thalamic degree centrality, t(33) = 2.17, p =.038. SCD14 predicted lower thalamic DC, b = -1.16, p =.035. Degree centrality predicted fatigue, b = -4.50, p =.03. Indirect and moderation effects were not significant. Monocyte activation is feature of chronic HIV-infection that impacts the number of thalamic connections to whole brain. The reduced thalamic degree centrality is associated with greater neurobiological vulnerability for fatigue after menopause.
... These ratings are thought to reflect the homeostatic status during motor tasks mediated by afferent nerve fibers detecting the mechanical, metabolic, thermal, chemical, and hormonal state of various neurophysiological systems. Their projections to brain areas like the anterior insula and anterior cingulate cortex enable conscious awareness of these stimuli, which serves as a protective mechanism for the body (Craig, 2002;Lindquist et al., 2016). Therefore, exercise intensity-dependent homeostatic perturbations in the respective physiological subsystems during fatiguing motor tasks contribute to the development of negative affective valence. ...
Fatigue can be present as a trait characteristic or a state variable. Thereby, trait fatigue describes the fatigue experienced by an individual over a longer period of time (e.g., weeks, months), which is relatively stable and a symptom of various diseases (e.g., multiple sclerosis, chronic obstructive pulmonary disease). In contrast, activity-induced state fatigue is characterized by an acute and temporary reduction in motor or cognitive performance (i.e., motor or cognitive performance fatigue, respectively) as well as the subjective experience of exhaustion or weariness that occurs in the context of a specific motor or cognitive task (i.e., perceived motor or cognitive fatigue, respectively). Motor performance fatigue (e.g., decrease in maximal voluntary contraction force) depends on the muscle activation characteristics and contractile function of muscles, whereas cognitive performance fatigue (e.g., increase in reaction time) depends on the integrity of the central nervous system. The motor and cognitive task-induced increase in the perception of fatigue is influenced by the psychophysiological state of an individual. Motor and cognitive performance fatigue, as well as perceived motor and cognitive fatigue, are interdependent, depend on several modulating factors (e.g., characteristics of the task and subject), and are susceptible to perturbations in body homeostasis.
... Nevertheless, without participants' explicit labeling of their emotional experiences, it remains uncertain whether the observed affective responses can be reliably mapped onto conventional emotion labels. Given the wide theoretical variability in defining emotions-ranging from their role as predictors of decisions (Phelps & LeDoux, 2005), integration of interoceptive signals (Craig, 2002), survival-related autobiographical processes (LeDoux & Brown, 2017), socially constructed affect (Barrett, 2017), to game-theoretic strategies under evolutionary pressures (Glimcher, 2004)-it is clear that comparable affective responses alone cannot serve as definitive evidence for equivalent emotional experiences. ...
Measuring emotion remains a persistent challenge due to poor alignment between theoretical constructs and available measurement tools, as well as issues of underspecificity and low reliability. Dimensional approaches—especially those incorporating social-affective dimensions—are being explored for their potential to enhance the quality of emotional data. Recent advances in large language models (LLMs) offer a novel opportunity to improve both emotion measurement and communication, leveraging their exceptional pattern recognition capabilities and capacity for multi-modal generation. In this study, we investigate for the first time whether LLMs can successfully mediate human emotional communication through analogical representations—expressing feelings not by naming them, but by evoking them.
We utilized multi-dimensional affective ratings from 547 participants across eighteen emotion labels obtained in a prior study. Based on this human emotion representation and custom-designed prompts, an LLM generated both textual and high-resolution (1024 × 1024) image outputs for each label. Two independent raters selected ten texts and one image per label, which were then presented to a new sample of 138 participants via an online psychology experiment platform. Participants rated these multi-modal stimuli using the same multi-dimensional affective scale. Angular and Euclidean distance metrics were used to evaluate the similarity between participants’ affective responses and the original ratings.
Emotional experiences for fifteen out of eighteen emotion labels were successfully reconstructed through exposure to LLM-generated stimuli. However, three emotions—disgust, satisfaction, and gratitude—were not effectively conveyed through either modality. The results also highlighted contextual modulation of emotion expression, influenced by media format and individual mood pathology. Across all categories, image-based stimuli evoked stronger affective responses than text. Moreover, participants with elevated depressive symptoms exhibited heightened emotional reactivity to shared stimuli—a potential affective signature of depression, rather than a general emotional amplification.
This study introduces a novel pipeline for eliciting and transmitting human emotional experiences through language models using analogy as a bridge—a method that is both replicable and empirically validated. Still, establishing true equivalence of emotional experiences requires further theoretical and mathematical development. Future directions include incorporating physiological markers, comparing across LLM architectures, and refining generalizability for broader human-centered applications in affective computing.
... Subcortical components of the SAL are the ventral striatum, amygdala and the substantia nigra/ventral tegmental area (Seeley et al., 2007;Menon, 2015). The SAL network integrates sensory, cognitive and emotional information and thus contributes to multiple complex brain functions such as communication, social behavior and self-awareness (Menon and Uddin, 2010;Feng et al., 2021;Craig, 2002Craig, , 2010. In contrast, the DMN is active when at rest or engaged in internally focused tasks such as daydreaming, mind-wandering, or self-referential thinking. ...
Introduction
Most brain imaging studies on olfaction focus on short-term odorant stimuli, with few examining long-lasting odor exposure or its after-effects. In this study, we utilized resting-state fMRI (rsfMRI) to investigate the effects of prolonged odor exposure to lavender on brain activity and whether these persist post-exposure.
Methods
Fourteen healthy women underwent two fMRI sessions, conducted one week apart, in a randomized order. Both sessions included rsfMRI scans before, during, and up to 2 h after a 14 min exposure to either lavender essential oil or a non-odorant control.
Results
An Independent Component Analysis identified the salience network (SAL) and default mode network (DMN) as the most consistent resting-state networks. A two-factorial ANOVA revealed significant time-varying interaction effects between the SAL and DMN. During odor exposure, functional connectivity (FC) increased within the SAL, and a negative correlation between the SAL and DMN appeared, which intensified immediately after exposure. Two hours post-exposure, the FC between SAL and DMN turned positive.
Discussion
These findings suggest that prolonged odorant exposure to lavender can induce long-lasting brain effects detectable up to 2 h afterwards in women. This proof-of-concept study should be extended to other odorants and to men, and offers new possibilities for exploring the effects of aromatherapy or other odor exposure interventions on brain activity.
... Both these phenomena may be consistent with the concept of the Neural Subjective Frame, which proposes that continuous updating of information about visceral states constructs first-person conscious experiences (Park & Tallon-Baudry, 2014;Tallon-Baudry et al., 2018). Ascending transmission from visceral organs can be divided into two main types: parasympathetic or vagal afferents via cervical ganglia projecting to the solitary bundle nucleus of the brainstem, and sympathetic afferents via dorsal root ganglia projecting through the spinal cord to the brain (Craig, 2002). These signals of autonomic nervous activity are either transmitted to the cortex (Park & Blanke, 2019) or processed in subcortical structures and medial nucleus of the hypothalamus, and later projected to higher brain regions such as the hypothalamus, insular cortex, anterior cingulate cortex, and somatosensory cortex (Critchley & Harrison, 2013). ...
Our thought states change unconsciously. This study verified that the transference of thought states varies with fluctuations in autonomic nervous activity, and that this effect is modulated by interoceptive accuracy. The participants completed the heartbeat counting task (HCT) and vigilance task (VT). We assessed the participants' interoceptive accuracy based on their performance on the HCT. The VT is a simple attention task, and during this task, we asked the participants to report the content and contemplation of their thoughts. Consequently, participants with accurate interoception were more likely to remain in a highly contemplative thought state when sympathetic activity was activated. In contrast, the dominance of parasympathetic activity facilitated transitions to different thought states or experiences of less contemplative thought states in them. The results suggest that even subtle changes in bodily responses at rest can affect thought transitions in people with accurate interoception.
... Previous research has often explored interoception in relation to biological sensation and neural integration of signals from disparate neural and afferent nerves (Craig, 2002;2003;Herbert & Pollatos, 2012;Wiens, 2005). However, the idea of measuring interoception as a form of limited capacity attention which can be focused on physiological signals, raises the possibility that it can covary with other forms of attention, such as those to our internal streams of thought or external stimuli. ...
Interoceptive Attention refers to how an individual typically allocates their attentional resources to physiological signals. We do not, however, fully understand how Interoceptive Attention relates with other forms of internally focused attention, such as attention to internal thoughts (e.g., mind-wandering, reflection, worry), and whether these factors compete for limited attentional resources at the trait and state level. Across two Studies (n = 222, n = 109; years data collected: 2021–2022, 2023-2024; from a UK-based predominantly undergraduate population), we isolated two components from several established trait-level measures of attention to thoughts, these reflected Negative Automatic Thoughts (worry, rumination), and Controlled Thoughts (deliberate mind-wandering, reflection). In subsequent regression analyses, Negative Automatic Thoughts, but not Controlled Thoughts, were a significant positive predictor of Interoceptive Attention, even when controlling for perceived interoceptive accuracy. This significant relationship was, however, accounted for by trait anxiety when included in the model. To test this pattern at the state-level, a novel monotonous responding task with three-dimensional attention probes was developed, which measures the reported allocation of attention between thoughts, bodily sensations, and the task. In contrast to trait-level attention, reported priority of attention to thoughts and body signals inversely correlated, despite both increasing across the task. The results suggest that in a single moment attention to bodily signals and internal thoughts may compete; but over time, individuals who report focusing more on their internal thoughts also report more time attending to their body, with some evidence showing that this positive correlation could be due to underlying trait anxiety.
... A secondary analysis was performed using data from a randomized, double-blind, sham-controlled feasibility clinical trial that was conducted to investigate the feasibility and safety of a source-localized EEG-NF for the management of chronic pain secondary to knee OA. The study aimed to modulate ISF electrical activity in the three cortical regions associated with pain processing, namely the dorsal anterior cingulate cortex (dACC), a cortical hub processing the affective/motivational component of pain (Rainville 2002;Bushnell et al. 2013;Price 2000;Vogt and Sikes 2000); the primary somatosensory cortex (S1), a proxy for processing the discriminative/sensory component of pain (Gingold et al. 1991;Craig 2002;Bushnell et al. 1999), and the pregenual anterior cingulate cortex (pgACC); part of the cortical pain inhibitory pathway (Kwon et al. 2014;Ossipov et al. 2014;Vanneste et al. 2017). ...
Introduction
Persistent musculoskeletal pain is associated with altered functional and effective connectivity (EC) between cortical regions involved in pain processing. Especially, disruptions in the infraslow fluctuation (ISF) frequency band can contribute to pain persistence. ISF electroencephalography‐neurofeedback (EEG‐NF) has emerged as a potential non‐invasive neuromodulatory intervention targeting cortical brain regions to restore balance and modulate pain‐related pathways. However, limited research explores its effect on EC, a measure of directional information flow critical to pain experience and modulation.
Methods
A secondary analysis was performed using data from a randomized, double‐blind, sham‐controlled feasibility clinical trial. Participants with chronic painful knee osteoarthritis (OA) were randomized to receive either ISF‐NF or sham‐NF. Nine neurofeedback sessions targeted the pregenual anterior cingulate cortex (pgACC), dorsal anterior cingulate cortex (dACC), and bilateral primary somatosensory cortex (SSC: S1Lt & S1Rt). EEG data was collected at baseline and post‐intervention. Granger causality was used to measure EC changes, and between‐group statistical analyses were conducted with adjustments for multiple comparisons.
Results
Twenty‐one participants (mean age: 61.7 ± 7.6 years; 62% female) completed the study. ISF‐NF training significantly improved EC between pgACC and dACC, pgACC and SSC, and other targeted regions, while reducing EC from S1Rt to dACC. Changes were observed predominantly in the ISF frequency band, indicating enhanced cortical communication and modulation of pain pathways.
Conclusion
ISF‐NF training enhanced EC in cortical regions implicated in pain processing, supporting its potential as a neuromodulatory intervention for chronic musculoskeletal pain. Further trials are needed to confirm clinical efficacy and optimize protocol designs.
... The term "felt-sense" has been used to describe the "unclear edge" or vague sense of meaning that can come from body awareness [19]. When the body's internal state is noticed consciously, cognition is involved, and there are bidirectional brain-body messaging or oscillations [20,21]. Interoception is the scientific term for the awareness of body sensations [22] and exteroception refers to noticing sensations in or from the environment. ...
Natural and human-made disasters, community violence, climate change, and political instability engender mental health problems worldwide. Childhood traumas, now recognized as commonplace and global in nature, augment the urgent need for mental health interventions that are accessible and scalable. The World Health Organization has called for innovative strategies that extend beyond traditional cognitive approaches. Biologically based methods are gaining recognition for their significant role in affect regulation and wellness promotion. This paper explores the potential for interventions focusing on interoceptive awareness, or noticing sensations arising from the body, to address mental health challenges, especially relevant for populations affected by trauma. The Community Resiliency Model (CRM)®, a low-intensity, body-based intervention that cultivates interoceptive awareness, is described and compared to other well-being interventions. Available research studies, program evaluations and anecdotal reports are presented in addition to CRM’s biological and theoretical underpinnings. The neurobiology of trauma, interoception research, and the concept of neural synchrony are briefly introduced, further explaining the likely mechanism of action and an underlying rationale for the reported improvements in well-being and resilience among individuals and communities who learn CRM body awareness techniques. Given increasing global demand and limited access to conventional mental health services, CRM and the six core skills that are taught in this model offer a promising, transferable, self-care strategy. Community dissemination has the potential to expand access in underserved populations. This review concludes by suggesting future research directions, such as the exploration of biophysical outcomes, intra- and interpersonal synchrony, and evaluation of interoceptive training for emotional regulation and populations affected by trauma or violence.
... Previous research has often explored interoception in relation to biological sensation and neural integration of signals from disparate neural and afferent nerves (Craig, 2002;2003;Herbert & Pollatos, 2012;Wiens, 2005). However, the idea of measuring interoception as a form of limited capacity attention which can be focused on physiological signals, raises the possibility that it can covary with other forms of attention, such as those to our internal streams of thought or external stimuli. ...
Interoceptive Attention refers to how an individual typically allocates their attentional resources to physiological signals. We do not, however, fully understand how Interoceptive Attention relates with other forms of internally focused attention, such as attention to internal thoughts (e.g., mind-wandering, reflection, worry), and whether these factors compete for limited attentional resources at the trait and state level. Across two Studies (n = 222, n = 109; years data collected: 2021–2022, 2023-2024; from a UK-based predominantly undergraduate population), we isolated two components from several established trait-level measures of attention to thoughts, these reflected Negative Automatic Thoughts (worry, rumination), and Controlled Thoughts (deliberate mind-wandering, reflection). In subsequent regression analyses, Negative Automatic Thoughts, but not Controlled Thoughts, were a significant positive predictor of Interoceptive Attention, even when controlling for perceived interoceptive accuracy. This significant relationship was, however, accounted for by trait anxiety when included in the model. To test this pattern at the state-level, a novel monotonous responding task with three-dimensional attention probes was developed, which measures the reported allocation of attention between thoughts, bodily sensations, and the task. In contrast to trait-level attention, reported priority of attention to thoughts and body signals inversely correlated, despite both increasing across the task. The results suggest that in a single moment attention to bodily signals and internal thoughts may compete; but over time, individuals who report focusing more on their internal thoughts also report more time attending to their body, with some evidence showing that this positive correlation could be due to underlying trait anxiety.
... Interoception, the sensing of internal bodily states, is a fundamental aspect of physiological and psychological functioning. The brain constantly monitors and adjusts the state and function of our internal organs, including hunger, thirst, respiratory, and cardiac functions (Craig, 2002). Research has shown that the neural processing of visceral signals contributes to a wide range of emotional, perceptual, and cognitive processes Critchley & Harrison, 2013;Quigley et al., 2021). ...
The brain continuously receives interoceptive information about the state and function of our internal organs. For instance, each time the heart beats, the brain responds by generating time-locked activity, known as heartbeat-evoked potentials (HEP). When investigating HEPs, it is essential to adequately control for heartbeat-independent confounding activity to avoid false interpretations. In the present study, we highlight the pitfalls of uncontrolled analyses and advocate for the use of surrogate heartbeat analysis and pseudotrial correction, which are promising tools to control for spurious results. Surrogate heartbeat analysis involves shuffling the timing of heartbeats to verify the time-locking of HEP effects. Pseudotrial correction works by subtracting heartbeat-independent activity from HEPs. In this study, we employ both procedures, validate them in simulations, and apply them to real electroencephalography (EEG) data. Using EEG recordings obtained during the performance of an auditory novelty oddball task in a large population, we show that, without control analyses, pre-stimulus HEPs appear inversely related to task-related measures such as P300 event-related potential amplitudes and reaction time speed. However, these effects disappear after carefully controlling for heartbeat-unrelated EEG activity. Additionally, in real and simulated data, we show that pseudotrial correction has the potential to remove task-related confounds from HEPs, thereby uncovering real heartbeat-related effects that otherwise could be missed. This study, therefore, highlights issues that can arise when analyzing HEPs during tasks, provides solutions to overcome them, and gives recommendations for future studies to avoid pitfalls when analyzing and designing experiments involving HEPs.
... The insula, known as the "Island of Reil", is located deep in the lateral sulcus [1] and extensively interconnected with other brain regions [1,2]. Supported by an extensive network of connections, the insula represents an integrative hub in the emotion and salience network [3,4] and plays a vital role in the integration of external-oriented sensory input and internal-oriented awareness [5,6]. The insula is a cytoarchitectonically and functionally heterogenous region organized along a posterior-to-anterior gradient such that the anterior insula (AI) is mainly involved in interoceptive processing [7][8][9], emotion [10], risky decisionmaking [11] and empathy [12,13], while the posterior insula (PI) primarily integrates somatosensory, vestibular, and motor information by receiving afferent projections from the spinal cord and brainstem via the thalamus [1]. ...
Real-time fMRI (rtfMRI) neurofeedback (NF) is a novel noninvasive technique that permits individuals to voluntarily control brain activity. The crucial role of the insula in emotional and salience processing makes it one of the most commonly targeted regions in previous rtfMRI studies. To provide an overview of progress in the field, the present review identified 25 rtfMRI insula studies and systematically reviewed key characteristics and findings in these studies. We found that rtfMRI-based NF training is efficient for modulating insula activity and its associated behavioral/symptom-related and neural changes. Furthermore, we also observed a maintenance effect of self-regulation ability and sustained symptom improvement, which is of importance for clinical application. However, training success of insula regulation was not consistently paralleled by behavioral/symptom-related changes, suggesting a need for optimizing the NF training protocol enabling more robust training effects. Principles including inclusion of a well-designed control group/condition, statistical analyses and reporting results following common criteria and a priori determination of sample and effect sizes as well as pre-registration are also highly recommended. In summary, we believe our review will inspire and inform both basic research and therapeutic translation of rtfMRI NF training as an intervention in mental disorders particularly those with insula dysfunction.
... displeasure-that accompany external perceptions plays an important role in psychoanalytic theory (Freud, 1900;Freud, 1925). It is also the subject of a number of recent neuroscientific investigations (Damasio, 1994;Prochiantz, 2000;Craig, 2002Craig, , 2003. Thus, these two disciplines find common ground around a homeostatic understanding of psychic functioning-particularly that of thought. ...
This article introduces a model of dialogue between psychoanalysis and neuroscience that is based on an account of the economic dimension of trauma. From the outset Freudian theory took into account the singularity of each subject’s response to traumatic events, setting aside any linear paradigm in the causality of symptoms. In 1980, the introduction of the nosographic category of PTSD (post-traumatic stress disorder) within the DSM (Diagnostic and Statistical Manual) contributed to an increased social recognition for sufferers. Yet, it also resulted in a form of standardization in a clinical picture that hitherto had been heterogenous. The result was a deterministic and linear epistemological paradigm whose effects could be normative. Once we have defined the opposition between these two paradigms, we propose demonstrating that a dialogue is possible between psychoanalysis and neuroscience around the concept of ‘trauma’. To do this we will introduce an interdisciplinary approach that is free of the pitfall of determinism, and that seeks to promote the consideration of singularity in clinic practice. From that perspective, the post-traumatic symptom is no longer viewed as the consequence of a particular event, rather it is a construct produced by the subject in their effort to manage what overwhelms them.
... Mehling et al. (2012) defines this as the "psychological aspects of the perception and evaluation of bodily states". This is because interoception is known to relate to understanding, experiencing, and regulating emotions (Craig, 2002;Herbert and Pollatos, 2012;Ventura-Bort et al., 2021). Since how interoception and food disgust may be related is as of yet unknown, this secondary objective was tested here. ...
... All trials from one subject were held out (5a), while ARHMM models were fit to data from the remaining twenty-nine subjects under each condition (5b), resulting in a total of thirty ARHMM models for both the control and iNM conditions. From the autoregressive (AR) coefficients for these models (6), the average confusion matrices representing connectivities between regions-of-interest (ROIs) were calculated (7). AR coefficients were subsequently grouped by network (8; i.e. motor, sensory, attention, reward), and confusion matrices representing network-to-network connectivities were similarly computed (9). ...
Introduction: Adequate sensory inputs and motor control are essential components of safe swallowing, with significant impact on both quality of life and patient survival. Conversely, both of these neuronal activities are negatively impacted during the early phases of ALS development, following instrumentation of the cervical spine through an anterior approach and broadly by delivery of surgical and radiation-based treatments for head and neck cancer. Our goal is to demonstrate the feasibility, and preliminary efficacy of the individualized fMRI neuromodulation (iNM) intervention pioneered by the Papageorgiou Lab (U.S. Patent No.16/954,256; European Patent No. 19 753 851.5) in enhancing tongue motor and sensory control (TMSC) in these variable patient populations. Although clinical trials show that steroids (NCT04151082) and gabapentin (NCT03747562) temporarily reduce pain, their adverse effects compromise tolerance and adherence. Thus, we need new treatments. The goal here was to strengthen networks that regulate TMSC through our individualized fMRI AI-NeuroModulation, termed iNM fMRI measures the magnitude and spatial extent of the ratio of oxygenated (O2) to deoxygenated hemoglobin (Hb). Our non-invasive, precision-medicine AI-iNM intervention: (1) target primary motor and sensory areas in the brain that regulate swallowing with 1mm level precision, (2) targets each patient's unique anatomical motor and sensory extents , and (3) iNM is and are guided by reinforcing or inhibiting the HbO2 intensity and extent of each patient's unique brain network, as opposed to self-regulation of the HbO2 intensity.
Methods: Thirty healthy subjects participated in a 2-day study which included iNM and control conditions. We first computed the individualized TMSC cortical selectivity to be targeted in the iNM condition. Support vector machine (SVM) classified cortical tongue direction and tongue-at-rest patterns generated via iNM and control. We quantified the BOLD magnitude for each network by computing the area under the curve (AUC), variance and association between brain states and TMSC responses via dynamic causal modeling (DCM).
Results: The mechanisms associated with attention-memory and sensorimotor iNM are: 1. 45% increase in the AUC's BOLD magnitude (p<0.001); 2. 14% decrease in the BOLD's intensity variance (p<0.01); and 3. 20% increase in network expansion (p<0.001). DCM uncovered 97% of the trials as pure motor signal, while 3% were noise in the iNM condition (compared to 83% of the TMSC trials and 17% noise in the control condition): 1. 70% motor-to-motor (M1, motor cerebellum, basal ganglia) and 70% motor-to-sensory; 2. 69% sensory-to-sensory (intraparietal lobule, insula, claustrum, sensory cerebellum, ACC); and 3. 70% sensorimotor-to-attention-memory network connectivities.
Conclusion: iNM showed spatiotemporal causality between networks that regulate motor and sensory control, which can serve as clinical biomarkers for the RICN alleviation in head and neck cancer survivors.
... Interoception is defined as the perception of the internal state of the body, including a wide range of physical states like heart rate, respiration, temperature, fatigue, hunger, satiety, muscle ache, and pain (Craig, 2002(Craig, , 2003(Craig, , 2009Murphy et al., 2019). Research in the field of interoception has increased over the years, which has provided a better understanding of the important role of interoception in physical and mental well-being. ...
Interoception, the perception of internal bodily signals, is thought to play a key role in health behavior. Interoceptive domains (e.g., accuracy and attention) are associated with mental disorders in various ways, underscoring the need for specific measures for different interoceptive domains. To allow for studying interoceptive domains in the Dutch population, the current study aimed to investigate the reliability and validity of Dutch translations of the Interoceptive Accuracy Scale (IAS-D) and Interoceptive Attention Scale (IATS-D).
In a sample of 779 participants (mean age 52.98 ± 16.47, 49.6% female), the IAS-D showed good internal consistency (α = 0.89) with a four-factor structure according to the confirmatory factor analysis (CFI = 0.816, TLI = 0.788, RMSEA = 0.084). The IAS-D had significant negative relations to the Interoceptive Confusion Questionnaire (β = -0.638, p < 0.001), depression (β = -0.298, p < 0.001), and alexithymia (β = 0.528, p < 0.001). The IATS-D showed good internal consistency (α = 0.94) with a three-factor structure according to the confirmatory factor analysis (CFI = 0.852, TLI = 0.833, RMSEA = 0.100). The IATS-D had significant positive relations with the Interoceptive Confusion Questionnaire (β = 0.481, p < 0.001), Body Perception Questionnaire (β = 0.207, p < 0.001), depression (β = 0.377, p < 0.001), and alexithymia (β = 0.528, p < 0.001).
The IAS-D and IATS-D are considered reliable and valid instruments for assessing self-reported interoceptive accuracy and attention in Dutch-speaking populations, supporting public health research on the role of interoception in health behavior.
Background: Acute visceral pain is among the most common symptoms of patients seeking in-hospital treatment and is related to various thoracic, abdominal, and pelvic diseases. It is characterized by distinguishable sensory qualities and can be described on a sensory-discriminative and affective-motivational level. These sensory qualities correlate with the activation of cerebral areas involved in the neuronal processing of visceral pain and can be visualized using functional neuroimaging. Methods: An ALE (activation likelihood estimation) meta-analysis of a total of 21 studies investigating different balloon distention paradigms during either PET or fMRI was performed to demonstrate the neuroanatomical correlates of visceral pain. The ALE meta-analysis was performed using the GingerAle software version 3.0.2 and was displayed with the Mango software 4.1 on an anatomical MNI template. Results: Summarizing studies investigating the functional neuroanatomy of visceral pain, bihemispheric activation of the insula, the thalamus, and clusters involving the right inferior parietal lobe/postcentral gyrus as well as the left postcentral gyrus/parietal inferior lobe were observed. Conclusions: This ALE meta-analysis substantiates the concept of two distinguishable neuroanatomical pathways of visceral pain which are related to either the sensory-discriminative or the affective-motivational dimension of pain processing.
This chapter explores the interplay between exercise intensity and attentional focus, highlighting the role of interoceptive feedback in shaping perceptual and affective responses. Selective attention and modulation are critical facets that shape how individuals allocate cognitive resources during physical activity. Integration of interoceptive feedback influences the way these attentional processes function at varying exercise intensities. During endurance exercise, two broad categories of attentional focus have been identified: association, the monitoring of internal sensory input, and dissociation, which involves diverting attention away from internal sensations toward external stimuli. With increasing exercise intensity, attentional focus shifts toward association, driven by the dominance of interoceptive cues over cognitive factors. We introduce influential theories that explain how this attentional shift critically impacts psychophysical responses and affective states. Neural evidence underscores the role of the dorsolateral prefrontal cortex in affect regulation at moderate to high levels of exercise intensity, with reference to its inhibitory control over the amygdala and other subcortical regions. The dissociative sensory experience associated with audiovisual stimuli may be linked to brain regions that moderate interoceptive awareness, thereby optimizing the exercise experience. This chapter lays the foundation for further exploration into attention-intensity dynamics during different modes of exercise in ecologically valid settings.
This chapter presents a comprehensive protocol for designing experiments aimed at collecting high-fidelity biological signals during movement-based activities such as walking, cycling, and running. It serves as a critical guide for researchers and students, emphasizing the importance of methodological rigor in preserving the integrity of psychophysiological data. Detailed steps are provided for adjusting experimental protocols to minimize the effects of physiological, mechanical, and environmental artifacts that can distort biological signals. The chapter also offers an in-depth look at preprocessing techniques for artifact removal, crucial for preparing electroencephalography (EEG) and heart rate variability (HRV) data for analysis. Readers are guided through a series of preprocessing approaches, including frequency decomposition and connectivity analysis, to ensure that extracted variables remain relevant and reliable. This practical framework equips readers with the knowledge to implement robust protocols and process psychophysiological data with accuracy, paving the way for reproducible and insightful research outcomes in exercise science.
Electricity generation by mine hoists during cargo transportation. Purpose of the work: testing the null hypothesis H0, according to which the operating mode of the hoist for electricity generation has no significant impact on economic indicators. Research methods: experiments to determine electricity generation by cage hoists during the day; testing the null hypothesis using logit regression. Research objects: cage hoists of the "Sukha Balka" mine. Results: the null hypothesis is unfair.
Keywords: cage hoists, electricity recovery, operating modes, null hypothesis.
Autism has historically been defined by the presence of differences in social communication and restricted, repetitive patterns of behavior, interests, or activities (RRBs). Since 2013 when the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders was published, sensory features were added as one of the polythetic restricted and repetitive behavior diagnostic criteria of autism, though it has remained understudied. Here, we summarize theory and research to provide support for the perspective that early sensory functions and experiences play a primary role in autism and have downstream effects on social communication and repetitive behavioral features of autism. The goals of this article are to provide an understanding of the current sensory research landscape over the early developmental period; to contextualize our knowledge autism within a developmental framework; to delineate a cascading developmental model that provides testable hypotheses; and to identify current gaps in research that would allow us to further our understanding of the role, and primacy of sensory differences in the development of the autistic phenotype. We close by offering a set of recommendations for the field.
In a context where AI is transforming organizational practices, this study aims to understand how AI and training impact the organizational resilience of SMEs. We adopt a qualitative approach based on thematic analysis of semi-structured interviews conducted with SMEs in the city of Agadir, Morocco. This analysis allowed us to explore participants' perceptions and experiences regarding AI and training. The results reveal that integrating AI into training constitutes a strategic lever for strengthening the organizational resilience of SMEs, despite implementation challenges related to cost, skills, and resistance to change.
There are several measures used to assess one's ability to perceive their heartbeat (cardiac interoceptive accuracy). These can be categorized into two main task types: tracking (e.g., motor tracking, heartbeat counting) and discrimination (e.g., two‐ and multi‐interval). The recently developed cardiovascular signal detection task (cvSDT) combines the advantages of heartbeat counting and multi‐interval discrimination tasks. It is an open question of how the three tasks relate to each other. This study compares all three methods in a sample of young adults (n = 73, 66% female). Efforts were made to identify heartbeat perceivers. Expectation and confidence ratings about perceived performance and interoception questionnaires were also administered. We found a relation between tracking and cvSDT(ρ = 0.401, p < 0.001); the multi‐interval task was unrelated to both other task types (tracking: ρ = −0.103, p = 0.398; cvSDT: ρ = −0.103, p = 0.398). Multiple linear regression analyses (with the control of resting heart rate, body fat percentage, and sex) confirmed these results. 27.4% of the sample were heartbeat perceivers according to the heartbeat counting task, 28.8% according to the multi‐interval discrimination task, and 12.3% according to the cvSDT. There was only one heartbeat perceiver according to all three tasks. Among questionnaires and tasks, only one connection was revealed: the Body Awareness Questionnaire related to the bias in cvSDT (ρ = −0.283*, p < 0.05). In summary, the three tasks likely assess partly different abilities. The investigation of expectation and confidence also supports this assumption. When choosing the method of cardiac interoception, characteristics should be considered to fit the research question.
Background/Objectives: The human insula is a key structure implicated in integrating internal states and external food cues, yet its precise role remains unclear, in part due to the temporal limitations of neuroimaging techniques like fMRI. To address this gap, we conducted an exploratory study using an intracranial EEG (iEEG) to investigate how the insula encodes both the subjective and objective properties of food-related stimuli, and how this encoding is modulated by hunger and satiety. Methods: Eight patients with drug-resistant epilepsy undergoing a pre-surgical evaluation between 2017 and 2023 participated in this study. Depth electrodes implanted in the insular cortex recorded event-related potentials (ERPs) in response to visual food cues. The sessions were conducted in two prandial states (hungry and satiated). The subjective ratings (appetite and palatability) and objective nutritional values (e.g., calories, carbohydrates) were collected and analyzed using paired t-tests, MANOVAs, and partial correlations. Results: Hunger increased the ERP amplitudes within the 350–450 ms interval, consistent with the EPIC model and positive alliesthesia, while satiety unexpectedly enhanced the early responses (150–250 ms). Importantly, the neural activity related to nutritional values was largely uncorrelated with the subjective ratings, suggestive of distinct processing streams. The mid- and posterior insula showed greater sensitivity to both subjective and nutritional information than the anterior insula. Conclusions: These findings offer novel electrophysiological insights into how the insula differentiates between implicit and explicit food-related signals, depending on the homeostatic state. This work supports a dual-route model of food cue processing, and may inform interventions targeting insular activity in disordered eating.
Introduction
Recent studies highlighted the importance of non-motor symptoms, including emotional processing dysfunction, in individuals with cervical dystonia (CD). The resting state functional connectivity of areas involved in emotional processing, and the modulatory role of social anxiety on this connectivity, remain unexplored in CD. We hypothesized that CD patients would have altered functional connectivity between limbic areas involved in emotional processing as compared to healthy subjects and examined how variations in social anxiety affect connectivity.
Methods
14 CD patients and 26 age- and sex-matched healthy controls completed a series of questionnaires and underwent functional magnetic resonance imaging (fMRI). Resting state functional connectivity was investigated between seeds (amygdala and insula) and whole brain ROIs, and in conventional functional networks. The modulatory role of social anxiety was investigated.
Results
CD patients showed reduced intra-regional connectivity in the insula, reduced connectivity between the right insula, left parietal operculum and left central opercular cortex. CD patients also showed clear reductions in connectivity in the salience, dorsal attention and sensorimotor resting state networks, as well as modest inter-network connections between language and fronto-parietal networks. In CD patients, higher anxiety scores and performance on affect naming tasks were associated with lower connectivity between right and left insula and between right insula and left central opercular cortex.
Conclusion
This study demonstrates that the previously observed deficits in emotional processing in CD patients may be underpinned by reduction in resting state functional connectivity in limbic areas and salience network with anxiety and social perception as a modulating factor.
This chapter provides an overview of the fascinating realm of interoception, the intricate process by which we perceive and interpret internal bodily sensations. In the following pages, I provide an overview of the ongoing debates regarding how we define and measure interoception, unraveling the challenges inherent in delineating the boundaries of our sensory experiences—how we sense, interpret, and integrate signals from within ourselves and our environment. Moving forward, I outline three prominent measurement models of interoception, critically evaluating their strengths and limitations, and highlighting directions for future conceptualizations. I then overview key measurement paradigms, focusing on cardiac and respiratory tasks as yogic practices commonly draw attention to these sensations. In addition, I provide an overview of six key self-report measures, and discuss the utility of ecological momentary assessment in capturing real-time interoceptive experiences. Finally, I examine the relationship between interoception and yoga, synthesizing clinical and non-clinical research on the intersections between these two fields. I hope this chapter not only broadens your understanding of interoception, but also underscores its significance in the context of yoga and its potential impact on overall well-being.
At the start of the twenty-first century, Arthur D. (Bud) Craig brought back to the fore the Island of Reil (insular cortex or insula). He did so by following, step by step, with rigor and tenacity, the afferent sensory pathway that informs the forebrain about the ongoing physiological status of the organs and tissues of the body. Along with his demonstration of the existence of a primate-specific ascending interoceptive pathway and his subsequent re-interpretation of Sherrington’s concept of interoception, Bud Craig’s seminal experiments and profound interpretations led him to make the groundbreaking proposals that the dorsal posterior insular cortex provides an ideal substrate for James’s concept of emotional embodiment, that the insular cortex contextualizes interoception across a posterior-to-mid-to-anterior integration with multimodal activities, and that the anterior insular cortex has a crucial role in the evolutionary emergence of the awareness of subjective feelings in humans, for the purpose of optimizing metabolic energy usage. Bud Craig’s unique work paves the path for further elucidation of the role of the insula and other brain regions in subjective feelings. His discoveries and proposals rest on implacable attention to neuroanatomical and neurophysiological details and a serendipitous quest for the fundamental evolutionary Logic of Life. This chapter provides a detailed description of the ascending interoceptive pathway and the functional and comparative neuroanatomy of the insular cortex in primates. Building on Bud Craig’s work, our recent findings suggest that the primary interoceptive cortex serves as a representation of the spino-solitary-parabrachial neuraxis, merging with posterior-to-mid-anterior and dorsal-to-ventral processing streams that form a latticework integration pattern. At the ventral anterior tip of this integration, the von Economo neuron area closes the corticofugal interoceptive-autonomic loop of the sensory-motor homeostatic system through projections to all brainstem nuclei integrating interoceptive afferences.
The research aims to systematize the current scientific evidence on methodologies used to investigate the impact of the indoor built environment on well-being, focusing on indoor environmental quality (IEQ) variables such as thermal comfort, air quality, noise, and lighting. This systematic review adheres to the Joanna Briggs Institute framework and PRISMA guidelines to assess empirical studies that incorporate physiological measurements like heart rate, skin temperature, and brain activity, which are captured through various techniques in real-life contexts. The principal results reveal a significant interest in the relationship between the built environment and physiological as well as psychological states. For instance, thermal comfort was found to be the most commonly studied IEQ variable, affecting heart activity and skin temperature. The research also identifies the need for a shift towards using advanced technologies like Mobile Brain/Body Imaging (MoBI) for capturing real-time physiological data in natural settings. Major conclusions include the need for a multi-level, evidence-based approach that considers the dynamic interaction between the brain, body, and environment. This study advocates for the incorporation of multiple physiological signals to gain a comprehensive understanding of well-being in relation to the built environment. It also highlights gaps in current research, such as the absence of noise as a studied variable of IEQ and the need for standardized well-being assessment tools. By synthesizing these insights, the research aims to pave the way for future studies that can inform better design and policy decisions for indoor environments.
Gargalesis, or tickle, is one of the most trivial yet enigmatic human behaviors. We do not know how a touch becomes ticklish or why we respond to other people’s tickles but not our own. No theory satisfactorily explains why touch on some body areas feels more ticklish than on others or why some people are highly sensitive while others remain unresponsive. Gargalesis is likely the earliest trigger for laughter in life, but it is unclear whether we laugh because we enjoy it. Socrates, Aristotle, Bacon, Galileo, Descartes, and Darwin theorized about tickling, but after two millennia of intense philosophical interest, experimentation remains scarce. This review argues that gargalesis is an exhilarating scientific puzzle with far-reaching implications for developmental, sensorimotor, social, affective, clinical, and evolutionary neuroscience. We reflect on the challenges in defining and eliciting ticklish sensations in the lab and unraveling their neural mechanism, discuss five classic yet unanswered questions about tickle, and suggest directions for future research.
The ability of the forebrain to track and integrate respiratory signals, a process known as breathing interoception, is critical for detecting respiratory threats and ensuring survival, yet its neural mechanisms remain largely unknown. Using human intracranial recordings, we identified widespread synchronization between forebrain neural oscillations and breathing rhythms across wakefulness, sleep, and external mechanical ventilation. During wakefulness, localized sites within known interoceptive regions such as insula, somatosensory cortex, anterior cingulate cortex, and amygdala robustly synchronized with breathing, highlighting their critical roles in breathing interoception. During sleep, forebrain synchronization shifted from cortex to amygdala and hippocampus, suggesting redistributed processing that may support vigilance and memory consolidation. In contrast to rodents, nasal airflow was not required for this synchronization, implicating multiple afferent pathways in respiratory interoception and possible unique evolutionary changes in humans. When breathing was driven by an external mechanical ventilator, the imposed breathing rhythm directly entrained forebrain activity, indicating a causal link. Notably, ventilator-driven slow, deep breathing entrained more forebrain sites, suggesting a potential mechanism through which breath-based practices might influence emotion and cognition. Together, these findings redefine breathing interoception as a pervasive influence within the forebrain, with implications for understanding disorders of respiratory awareness, emotional regulation, and cognitive health.
Aligning one’s decisions with the prevailing norms and expectations of those around us constitutes a fundamental facet of moral decision-making. When faced with conflicting moral values, one adaptive approach is to rely on intuitive moral preference. While there has been theoretical speculation about the connection between moral preference and an individual’s awareness of introspective interoceptive signals, it has not been empirically examined. This study examines the relationships between individuals’ preferences in moral dilemmas and interoception, measured with self-report, heartbeat detection task, and resting-state fMRI. Two independent experiments demonstrate that both male and female participants’ interoceptive awareness and accuracy are associated with their moral preferences aligned with group consensus. In addition, the fractional occupancies of the brain states involving the ventromedial prefrontal cortex and the precuneus during rest mediate the link between interoceptive awareness and the degree of moral preferences aligned to group consensus. These findings provide empirical evidence of the neural mechanism underlying the link between interoception and moral preferences aligned with group consensus.
Significance statement We investigate the intricate link between interoceptive ability to perceive internal bodily signals and decision-making when faced with moral dilemmas. Our findings reveal a significant correlation between the accuracy and awareness of interoceptive signals and the degree of moral preferences aligned with group consensus. Additionally, brain states involving the ventromedial prefrontal cortex and precuneus during rest mediate the link between interoceptive awareness and moral preferences aligned with group consensus. These findings provide empirical evidence that internal bodily signals play a critical role in shaping our moral intuitions according to others’ expectations across various social contexts.
Research on nonhuman primates suggests that the primary taste cortex in humans is located in the rostrodorsal insula. Qualitative and quantitative assessment of taste perception was performed on 6 patients with unilateral damage to the insula, 3 patients with brain damage outside the insula, and 11 age-matched, normal subjects. Each subject identified the quality and intensity of the gustatory stimuli applied separately to the left and right sides of the anterior tongue. Damage to the right insula produced ipsilateral taste recognition and intensity deficits. Damage to the left insula caused an ipsilateral deficit in taste intensity but a bilateral deficit in taste recognition. The unexpected deficit in the left-hemispheric stroke patients for taste recognition on the right side of the tongue suggests that taste information from both sides of the tongue passes through the left insula.
Assessments of anterior cingulate cortex in experimental animals and humans have led to unifying theories of its structural organization and contributions to mammalian behaviour The anterior cingulate cortex forms a large region around the rostrum of the corpus callosum that is termed the anterior executive region. This region has numerous projections into motor systems, however since these projections originate from different parts of anterior cingulate cortex and because functional studies have shown that it does not have a uniform contribution to brain functions, the anterior executive region is further subdivided into 'affect' and 'cognition' components. The affect division includes areas 25, 33 and rostral area 24, and has extensive connections with the amygdala and periaqueductal grey, and parts of it project to autonomic brainstem motor nuclei. In addition to regulating autonomic and endocrine functions, it is involved in conditioned emotional learning, vocalizations associated with expressing internal states, assessments of motivational content and assigning emotional valence to internal and external stimuli, and maternal-infant interactions. The cognition divi sion includes caudal areas 24' and 32', the cingulate motor areas in the cingulate sulcus and nociceptive cortex. The cingulate motor areas project to the spinal cord and red nucleus and have premotor functions, while the nociceptive area is engaged in both response selection and cognitively demanding information processing. The cingulate epilepsy syndrome provides important support of experimental animal and human functional imaging studies for the role of anterior cingulate cortex in movement affect and social behaviours. Excessive cingulate activity in cases with seizures confirmed in anterior cingulate cortex with subdural electrode recordings, can impair consciousness alter affective stare and expression, and influence skeletomotor and autonomic activity. Interictally, patients with anterior cingulate cortex epilepsy often display psychopathic or sociopathic behaviours. In other clinical examples of elevated anterior cingulate cortex activity it may contribute to ties, obsessive-compulsive behaviours, and aberrent social behaviour. Conversely, reduced cingulate activity following infarcts or surgery can contribute to behavioural disorders including akinetic mutism, diminished self-awareness and depression, motor neglect and impaired motor initiation, reduced responses to pain, and aberrent social behaviour. The role of anterior cingulate cortex in pain responsiveness is suggested by cingulumotomy results and functional imaging studies during noxious somatic stimulation. The affect division of anterior cingulate cortex modulates autonomic activity and internal emotional responses, while the cognition division is engaged in response selection associated with skeletomotor activity and responses to noxious stimuli. Over-all, anterior cingulate cortex appears to play a crucial role in initiation, motivation, and goal-directed behaviours. The anterior cingulate cortex is part of a larger matrix of structures that are engaged in similar functions. These structures from the rostral limbic system and include the amygdala, periaqueductal grey, ventral striatum, orbitofrontal and anterior insular cortices. The system formed by these interconnected areas assesses the motivational content of internal and external stimuli and regulates context-dependent behaviours.
We report the existence and distribution of an unusual type of projection neuron, a large, spindle-shaped cell, in layer Vb
of the anterior cingulate cortex of pongids and hominids. These spindle cells were not observed in any other primate species
or any other mammalian taxa, and their volume was correlated with brain volume residuals, a measure of encephalization in
higher primates. These observations are of particular interest when considering primate neocortical evolution, as they reveal
possible adaptive changes and functional modifications over the last 15–20 million years in the anterior cingulate cortex,
a region that plays a major role in the regulation of many aspects of autonomic function and of certain cognitive processes.
That in humans these unique neurons have been shown previously to be severely affected in the degenerative process of Alzheimer’s
disease suggests that some of the differential neuronal susceptibility that occurs in the human brain in the course of age-related
dementing illnesses may have appeared only recently during primate evolution.
The central role of the hypothalamus in the origination and/or processing of feeding-related stimuli may be modulated by the
activity of other functional areas of the brain including the insular cortex (involved in enteroceptive monitoring) and the
prefrontal cortex (involved in the inhibition of inappropriate response tendencies). Regional cerebral blood flow (rCBF),
a marker of neuronal activity, was measured in 11 healthy, normal-weight men by using positron emission tomography in a state
of hunger (after 36-h fast) and a state of satiation (after a liquid meal). Hunger was associated with significantly increased
rCBF in the vicinity of the hypothalamus and insular cortex and in additional paralimbic and limbic areas (orbitofrontal cortex,
anterior cingulate cortex, and parahippocampal and hippocampal formation), thalamus, caudate, precuneus, putamen, and cerebellum.
Satiation was associated with increased rCBF in the vicinity of the ventromedial prefrontal cortex, dorsolateral prefrontal
cortex, and inferior parietal lobule. Changes in plasma insulin concentrations in response to the meal were negatively correlated
with changes in rCBF in the insular and orbitofrontal cortex. Changes in plasma free fatty acid concentrations in response
to the meal were negatively correlated with changes in rCBF in the anterior cingulate and positively correlated with changes
in rCBF in the dorsolateral prefrontal cortex. In conclusion, these findings raise the possibility that several regions of
the brain participate in the regulation of hunger and satiation and that insulin and free fatty acids may be metabolic modulators
of postprandial brain neuronal events. Although exploratory, the present study provides a foundation for investigating the
human brain regions and cognitive operations that respond to nutritional stimuli.
Neural correlates of responses to emotionally valenced olfactory, visual, and auditory stimuli were examined using positron emission tomography. Twelve volunteers were scanned using the water bolus method. For each sensory modality, regional cerebral blood flow (rCBF) during presentation of both pleasant and unpleasant stimuli was compared with that measured during presentation of neutral stimuli. During the emotionally valenced conditions, subjects performed forced-choice pleasant and unpleasant judgments. During the neutral conditions, subjects were asked to select at random one of a two key-press buttons. All stimulations were synchronized with inspiration, using an airflow olfactometer, to present the same number of stimuli for each sensory modality. A no-stimulation control condition was also performed in which no stimulus was presented. For all three sensory modalities, emotionally valenced stimuli led to increased rCBF in the orbitofrontal cortex, the temporal pole, and the superior frontal gyru
Four adult male human subjects were tested under three conditions of internal body temperature: hypothermia, normal, and hyperthermia. Under each of these conditions, they judged the intensity (degree of warmness or coolness) and the hedonic quality (degree of pleasantness or unpleasantness) of a series of stimuli ranging from hot to cold. The results showed that whereas hedonic quality is greatly influenced by the value of internal body temperature, the perception of warmness or coolness is independent of internal temperature and dependent only on peripheral stimulation.
It has been known for over a century that there is an afferent (body-to-brain) component to the visceral-autonomic nervous system. Despite the fundamental importance of bodily afferent information - sometimes called interoception - to central nervous system control of visceral organ function, emotional-motivational processes, and dysfunctino of these processes, including psychosomatic disorders, its role did not receive much attention until quite recently. This is the first comprehensive review of this topic and it covers both neurobiological and psychobiological aspects. The author first defines the issues and gives an historical background starting with the James-Lange theory of emotion, and addresses learning and motivation, roots in Pavlovian conditioning research, and operant conditioning of visceral function. In the second section he reviews recent scientific findings in the neural basis of visceral perception and studies in cardiovascular-respiratory and alimentary interoception. Finally, he discusses several related areas of research and theory including drug state issues, interoception and psychiatric disorders, and bodily consciousness, and suggests directions for future investigation.
A unique text, relating the dramatic advances of modern neurobiology to the understanding of the structure and function of the autonomic nervous system. Written by an international group of distinguished scientists, it provides a clear view of the central neuronal components involved in autonomic control. Its scope is wide, ranging from anatomical pathways and molecular pharmacology to the perceptual qualities of autonomic sensation and their potential in modifying behaviour. The approach is mildly didactic, and combines concise background information with discussion of the latest research findings. It is richly illustrated with line drawings that concisely summarize concepts presented in the text.
1. Intraneural microstimulation (INMS) and microneurography were used in combination to stimulate and record from muscle nociceptor primary afferent fibers of the common peroneal nerve of healthy volunteers. When pain evoked by INMS was projected to muscle, afferent activity could be evoked by innocuous and noxious pressure applied within the projected painful area. Conduction velocity of single fibers was determined by stimulating the receptive fields (RFs) electrically via needle electrodes inserted into the RF and measuring conduction latency and distance between the RF and recording electrode. 2. Pain projected to muscle during INMS trains 5–10 s in duration at threshold intensity for pain sensation was typically described as cramping and was well localized. Subjects mapped the area of the painful projected field (PF) over the skin using a pointer. 3. Fourteen slowly adaping mechanoreceptors with RF in muscle and with moderate to high receptor threshold were identified within or near the painful PF. Conduction velocities were in the range of Group III (n = 8) and Group IV (n = 6) fibers. Mean RF areas of Group III and Group IV afferents, determined by applying pressure percutaneously, were 2.71 +/- 1.14 (SE) cm2 and 3.40 +/- 1.08 (SE) cm2, respectively. Only one Group III afferent unit exhibited spontaneous activity (< 1 Hz). 4. One additional high-threshold mechanoreceptor was identified, with its RF located in the extensor tendon at the base of the big toe. This fiber had a conduction velocity of 32 m/s. During INMS, a well-localized sharp pain was projected to the tendon.(ABSTRACT TRUNCATED AT 250 WORDS)
Unmyelinated afferents constitute a second system coding tactile stimuli of the human hairy skin. Impulses were recorded from unmyelinated afferents innervating the forearm skin of human subjects using the technique of microneurography. Units responding to innocuous skin deformation were selected. The sample ( n = 38) was split into low-threshold units ( n = 27) and high-threshold units ( n = 11) on the basis of three distinctive features, i.e., thresholds to skin deformation, size of response to innocuous skin deformation, and differential response to sharp and blunt stimuli. The low-threshold units provisionally were denoted tactile afferents on the basis of their response properties, which strongly suggest that they are coding some feature of tactile stimuli. They exhibited, in many respects, similar functional properties as described for low-threshold C-mechanoreceptive units in other mammals. However, a delayed acceleration, not previously demonstrated, was observed in response to long-lasting innocuous indentations. It was concluded that human hairy skin is innervated by a system of highly sensitive mechanoreceptive units with unmyelinated afferents akin to the system previously described in other mammals. The confirmation that the system is present in the forearm skin and not only in the face area where it first was identified suggests a largely general distribution although there are indications that the tactile C afferents may be lacking in the very distal parts of the limbs. The functional role of the system remains to be assessed although physiological properties of the sense organs invite to speculations that the slow tactile system might have closer relations to limbic functions than to cognitive and motor functions.
1. In recordings made from 2,925 single neurons, a region of primary taste cortex was localized to the rostral and dorsal part of the insula of the cynomolgus macaque monkey, Macaca fascicularis. The area is part of the dysgranular field of the insula and is bordered laterally by the frontal opercular taste cortex. 2. The responses of 65 single neurons with gustatory responses were analyzed in awake macaques with the use of the taste stimuli glucose, NaCl, HCl, quinine HCl (QHCl), water, and black currant juice. 3. Intensity-response functions showed that the lowest concentration in the dynamic part of the range conformed well to human thresholds for the basic taste stimuli. 4. A breadth-of-tuning coefficient was calculated for each neuron. This is a metric that can range from 0.0 for a neuron that responds specifically to only one of the four basic taste stimuli to 1.0 for one that responds equally to all four stimuli. The mean coefficient for 65 cells in the taste insula was 0.56. This tuning is sharper than that of neurons in the nucleus of the solitary tract of the monkey, and similar to that of neurons in the primary frontal opercular taste cortex. 5. A cluster analysis showed that at least six different groups of neurons were present. For each of the taste stimuli, glucose, NaCl, HCl, QHCl, water, and black currant juice, there was one group of neurons that responded much more to that tastant than to the other tastants. Other subgroups of these neurons responded to two or more of these tastants, such as glucose and black currant juice, or NaCl and QHCl. 6. On the basis of this and other evidence, it is concluded that the primary insular taste cortex, in common with the primary frontal opercular taste cortex, represents a stage of information processing in the taste system of the primate at which the tuning of neurons has become sharper than that of neurons in the nucleus of the solitary tract, and is moving toward the fineness achieved in the secondary taste cortex in the caudolateral orbitofrontal taste cortex, where motivation-dependence first becomes manifest in the taste system.
The projections from the parabrachial nucleus to the midline and intralaminar thalamic nuclei were examined in the rat. Stereotaxic injections of the retrograde tracer cholera toxin-β (CTb) were made in each of the intralaminar nuclei of the dorsal thalamus (the lateral parafascicular, medial parafascicular, oval paracentral, central lateral, paracentral, and central medial nuclei), as well as the midline thalamic nuclei (the paraventricular, intermediodorsal, mediodorsal, paratenial, rhomboid, reuniens, parvicellular part of the ventral posterior, and caudal ventral medial nuclei). The retrograde cell body labeling pattern within the parabrachial subnuclei was then analyzed. The paracentral thalamic nucleus received an input only from the internal lateral parabrachial subnucleus. However, this subnucleus also projected to all the other intralaminar thalamic nuclei, except for the central lateral thalamic nucleus, which received no parabrachial afferent inputs. The external lateral parabrachial subnucleus projected to the lateral parafascicular, reuniens, central medial, parvicellular part of the ventral posterior, and caudal ventromedial thalamic nuclei. Following CTb injections in the paraventricular thalamic nucleus, retrogradely labeled cells were found in the central lateral, dorsal lateral, and external lateral parabrachial subnuclei. The medial and ventral lateral parabrachial subnuclei projected to the oval paracentral, parafascicular, and rhomboid thalamic nuclei. Finally, the waist area of the parabrachial nucleus was densely labeled after CTb injections in the parvicellular part of the ventral posterior thalamic nucleus. Nociceptive, visceral, and gustatory signals may reach specific cortical and other forebrain sites via this parabrachial-thalamic pathway. J. Comp. Neurol. 428:475–494, 2000. © 2000 Wiley-Liss, Inc.
The hypothesis is presented that central pain is due to the disruption of thermosensory integration and the loss of cold inhibition of burning pain. This is a new variation on the thalamic disinhibition hypothesis originally proposed by H. Head and G. Holmes in 1911 (Brain 34:102-254). The thermal grill illusion of pain provides a model for this concept. Functional anatomic substrates are described that provide a sound framework for the hypothesis. Predictions are made and unresolved issues are addressed that provide opportunities to test this hypothesis.
The capacity to reflect on one’s sense of self is an important component of self‐awareness. In this paper, we investigate some of the neurocognitive processes underlying reflection on the self using functional MRI. Eleven healthy volunteers were scanned with echoplanar imaging using the blood oxygen level‐dependent contrast method. The task consisted of aurally delivered statements requiring a yes–no decision. In the experimental condition, participants responded to a variety of statements requiring knowledge of and reflection on their own abilities, traits and attitudes (e.g. ‘I forget important things’, ‘I’m a good friend’, ‘I have a quick temper’). In the control condition, participants responded to statements requiring a basic level of semantic knowledge (e.g. ‘Ten seconds is more than a minute’, ‘You need water to live’). The latter condition was intended to control for auditory comprehension, attentional demands, decision‐making, the motoric response, and any common retrieval processes. Individual analyses revealed consistent anterior medial prefrontal and posterior cingulate activation for all participants. The overall activity for the group, using a random‐effects model, occurred in anterior medial prefrontal cortex ( t = 13.0, corrected P = 0.05; x , y , z , 0, 54, 8, respectively) and the posterior cingulate ( t = 14.7, P = 0.02; x , y , z , –2, –62, 32, respectively; 967 voxel extent). These data are consistent with lesion studies of impaired awareness, and suggest that the medial prefrontal and posterior cingulate cortex are part of a neural system subserving self‐reflective thought.
Pain has traditionally been considered a primary sensory modality. Although pain mediates responses to injury of all bodily tissues, the vast majority of pain research has focused upon cutaneous sensation, the most superficial of the body components and the most experimentally accessible. Pain has therefore been viewed as an externally directed, somatosensory modality. Recent advances in understanding the pathways taken by visceral sensory afferents, as well as revelations about the pathways taken by pain afferents, have steadily eroded the classical concepts that kept these modalities in distinctly different classifications. In fact, the data reviewed in this chapter suggests that pain is itself a visceral sensory modality, originating from virtually all parts of the organism, but reaching perception in a way that is more typical of other visceral sensations than it is of the dorsal column systems with which it is more usually compared. Rather than being an outwardly directed sensory modality, whose purpose is to explore the external world, pain is intrinsically an inwardly directed modality. The role of pain is to identify tissue injury, whether it is due to an external source or an internal one, and to modify reflex responses and behaviors to minimize tissue damage. In this sense, pain can be conceptualized as a visceral sensory modality concerned with the internal body beginning one cell layer under the cornified epidermis.
This chapter discusses the major second-order central projection system that appears to have a fundamental role as a general homeostatic afferent system. It shows that projections from lamina I of the dorsal horn distribute activity originating from small-diameter input to several neural levels. This activity is functionally specific and relevant to the roles of the targeted regions in the physiological maintenance of the integrity of the body—that is, in homeostasis. Because lamina I projections convey such activity to a discrete nucleus in the primate thalamus and thence to insular cortex, in addition to spinal and brainstem levels. The chapter also reviews (1) the peripheral and central inputs to lamina I, (2) the physiological and morphological organization of lamina I, and (3) the projections of lamina I to spinal and supraspinal components of the autonomic and limbic systems. These findings are discussed with respect to the fundamental role of lamina I in relaying small-diameter afferent input from the body.
A unique text, relating the dramatic advances of modern neurobiology to the understanding of the structure and function of the autonomic nervous system. Written by an international group of distinguished scientists, it provides a clear view of the central neuronal components involved in autonomic control. Its scope is wide, ranging from anatomical pathways and molecular pharmacology to the perceptual qualities of autonomic sensation and their potential in modifying behaviour. The approach is mildly didactic, and combines concise background information with discussion of the latest research findings. It is richly illustrated with line drawings that concisely summarize concepts presented in the text.
There are many advantages to defining emotions as states elicited by reinforcers, with the states having a set of different functions. This approach leads towards an understanding of the nature of emotion, of its evolutionary adaptive value, and of many principles of brain design. It also Leads towards a foundation for many of the processes that underlie evolutionary psychology and behavioral ecology. It is shown that recent as well as previous evidence implicates the amygdala and orbitofrontal cortex in positive as well as negative emotions. The issue of why emotional states feel like something is part of the much larger problem of phenomenal consciousness. It is argued that thinking about one's own thoughts would have adaptive value by enabling first order linguistic thoughts to be corrected. It is suggested that reflecting on and correcting one's own thoughts and plans would feel like something, and that phenomenal consciousness may occur when this type of monitoring process is taking place.
The central neural pathways that convey somatosensory and visceral information to the hypothalamus and limbic system are organized in a parallel fashion. Both somatosensory and visceral stimuli reach the hypothalamus through monosynaptic and polysynaptic pathways that share the same origins and terminations (for example, lateral hypothalamus and amygdala). For example, nociceptive information can reach the hypothalamus directly through the spinal cord and indirectly through the parabrachial nuclei, and visceral information can reach the hypothalamus directly through the nucleus of the solitary tract (NTS) and indirectly through the parabrachial nuclei or ventrolateral medulla. Functionally, it is possible that under certain conditions (for example, tissue-threatening nociceptive stimuli) monosynaptic pathways can serve to convey the information more rapidly, while polysynaptic pathways can mediate more general responses (for example, alertness, adaptation, aversiveness and plasticity) that are processed by limbic and cortical structures and take into consideration previous experience and attitude.
This chapter summarizes the anatomical and functional organization of neural systems involved in effecting integrated visceromotor responses to stress, with an emphasis on hypothalamic neuroendocrine mechanisms. Implications for the nature of the interaction with the neural mechanisms subserving aspects of emotional experience and expression are discussed. The advent of “functional mapping” based on the induced expression of c-fos and other transcription factors has provided an extraordinarily powerful tool with which to glean a high-resolution profile of individual neurons and extended systems that are responsive to significant or “stressful” environmental events. Owing to the fact that no cellular immediateearly gene (cIE) is a perfect marker of synaptic and/or transcriptional activity, and uncertainties as to the significance of cIE expression at a cellular/molecular level under most circumstances, this technology seems best suited for use as a starting point from which to formulate hypotheses concerning situation-specific functional relatedness, which can then be tested experimentally. Such an approach has been most forthcoming in providing an initial level of definition of stress-specific operational circuits in several paradigms.
The author presents a discussion of the steady states (homeostases) of the body, with the explanation, so far as such is possible, of the mechanisms controlling such conditions. The account is closed with analogies between the regulation of the body and the regulation of social processes. Brief bibliography. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Are nonhuman animals conscious? When do babies begin to feel pain? What function is served by consciousness? What evidence could resolve these issues?
These questions are tackled by exploring psychologists' findings on topics as diverse as animal cognition, unconscious learning and perception in humans, infantile amnesia, theory of mind in primates, and the nature of pleasure and pain. Experimental results are placed in theoretical context by tracing the development of concepts of consciousness in animals and humans (from Plato to Penrose). Two themes emerge: first, the capacity for language marks a fundamental difference between humans and nonhumans; second, there is neither proof that any non-human species is conscious, nor any convincing function to be found for consciousness. Finally, a sketch is offered of a novel functionalist theory according to which the developing capacity for language allows the creation by infants of a 'self,' which may be a precondition for consciousness. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
We utilised retrograde and anterograde tracing procedures to study the origin and termination of prefrontal cortical (PFC) projections to the periaqueductal gray (PAG) in the rat. A previous study, in the primate, had demonstrated that distinct subgroups of PFC areas project to specific PAG columns. Retrograde tracing experiments revealed that projections to dorsolateral (dlPAG) and ventrolateral (vlPAG) periaqueductal gray columns arose from medial PFC, specifically prelimbic, infralimbic, and anterior cingulate cortices. Injections made in the vlPAG also labeled cells in medial, ventral, and dorsolateral orbital cortex and dorsal and posterior agranular insular cortex. Other orbital and insular regions, including lateral and ventrolateral orbital, ventral agranular insular, and dysgranular and granular insular cortex did not give rise to appreciable projections to the PAG. Anterograde tracing experiments revealed that the projections to different PAG columns arose from specific PFC areas. Projections from the caudodorsal medial PFC (caudal prelimbic and anterior cingulate cortices) terminated predominantly in dlPAG, whereas projections from the rostroventral medial PFC (rostral prelimbic cortex) innervated predominantly the vlPAG. As well, consistent with the retrograde data, projections arising from select orbital and agranular insular cortical areas terminated selectively in the vlPAG. The results indicate: (1) that rat orbital and medial PFC possesses an organisation broadly similar to that of the primate; and (2) that subdivisions within the rat orbital and medial PFC can be recognised on the basis of projections to distinct PAG columns. J. Comp. Neurol. 422:556–578, 2000. © 2000 Wiley-Liss, Inc.
To reveal brain regions and transmitter systems involved in control of pancreatic hormone secretion, specific vagal and sympathetic denervation were combined with injection of a retrograde transsynaptic tracer, pseudorabies virus (PRV), into the pancreas. After sympathetic or vagal transsection first-order neurons were revealed in the dorsal motor nucleus of the vagus (DMV) or in preganglionic spinal cord neurons (SPN), respectively. Careful timing of the survival of the animals allowed the detection of cell groups in immediate control of these DMV or SPN neurons. A far larger number of cell groups is involved in the control of DMV than of SPN neurons. Examples are given of a high level of interaction between the sympathetic and parasympathetic nervous system. Several cell groups project to both branches of the autonomic nervous system, sometimes even the same neurotransmitter is used, e.g., oxytocin neurons in the paraventricular nucleus and melanin-concentrating hormone and orexin neurons in the lateral hypothalamus project to both the DMV and SPN neurons. Moreover, the appearance of third-order neurons located in the sympathetic SPN after complete sympathectomy and in the DMV after complete vagotomy illustrates the possibility that motor neurons of the sympathetic and parasympathetic system may exchange information by means of interneurons. The presence of second-order neurons in prefrontal, gustatory, and piriform cortex may provide an anatomic basis for the involvement of these cortices in the cephalic insulin response. The observation that second-order neurons in both vagal and sympathetic control of the pancreas contain neuropeptides that are known to play a role in food intake indicates a direct association between behavioral and autonomic functions. Finally, the observation of third-order neurons in the suprachiasmatic nucleus and ventromedial hypothalamus shows the modulatory action of the time of the day and metabolic state, respectively.
Brain activity was studied by fMRI in 18 healthy subjects during stimulation of the thenar eminence of the hand with either warm (non-painful, 40 degrees C) or hot (painful, 46-49 degrees C) stimuli using a contact thermode. Experiments were performed on the right and left hand independently and with two attentional contexts: subjects either attended to pain or attended to a visual global motion discrimination task (to distract them from pain). Group analysis demonstrated that attended warm stimulation of the right hand did not produce any significantly activated clusters. Painful thermal stimulation of either hand elicited significant activity over a large network of brain regions, including insula, inferior frontal gyrus, cingulate gyrus, secondary somatosensory cortex, cerebellum, and medial frontal gyrus (corrected P < 0.05). Insula activity was distributed along its anterior-posterior axis and depended on the hand stimulated and attentional context. In particular, activity within the posterior insula was contralateral to the site of stimulation, tested using regions of interest (ROI) analysis: significant side x site interaction (P = 0.001). With attention diverted from the painful stimulus bilateral anterior insula activity moved posteriorly to midinsula and decreased in extent (ROI analysis: significant main effect of attention (P = 0.03)). The role of the insula in thermosensation and attention is discussed.
Recognition of facial expressions is critical to our appreciation of the social and physical environment, with separate emotions having distinct facial expressions. Perception of fearful facial expressions has been extensively studied, appearing to depend upon the amygdala. Disgust-literally 'bad taste'-is another important emotion, with a distinct evolutionary history, and is conveyed by a characteristic facial expression. We have used functional magnetic resonance imaging (fMRI) to examine the neural substrate for perceiving disgust expressions. Normal volunteers were presented with faces showing mild or strong disgust or fear. Cerebral activation in response to these stimuli was contrasted with that for neutral faces. Results for fear generally confirmed previous positron emission tomography findings of amygdala involvement. Both strong and mild expressions of disgust activated anterior insular cortex but not the amygdala; strong disgust also activated structures linked to a limbic cortico-striatal-thalamic circuit. The anterior insula is known to be involved in responses to offensive tastes. The neural response to facial expressions of disgust in others is thus closely related to appraisal of distasteful stimuli.
This article proposes a modification of the currently accepted view of the central neural integration of body temperature.
In place of a single integrator with multiple inputs and outputs, the new model includes as many integrators as there are
thermoregulatory responses. Futhermore, these integrators are postulated to be represented at many levels of the nervous system,
with each level facilitated or inhibited by levels above and below. The purpose of such a complicated arrangement is to achieve
finer and finer control over body temperature. A consideration of how endothermy might have evolved, with originally nonthermally
related responses gradually coming under thermal control, makes such a brain organization highly reasonable.
1. Impulses in cutaneous nerve fibres were recorded percutaneously with tungsten micro-electrodes from the superficial radial nerve of adult human subjects. 2. Eight units studied had conduction velocities below 1.5 m/sec, and thus belong to the class of C fibres. On the basis of their responsiveness to mechanical and to thermal stimuli the units were classified as 'polymodal nociceptors'. 3. Units were tested with 12 sec heat pulses starting from a base line temperature of 43.0-43.5 degrees C. Heat stimuli reaching three different maximal levels were applied in randomized order, the subjects being blind with respect to stimulus size. Each of the eight units studied was tested with more tha 20 stimuli and with four of them were 80-125 stimulus repetitions. 4. After each stimulus the subjects had to rate his sensations on a six-point rating scale extending from 'just noticeable' to 'very hot, painful'. 5. Discrimination between the three stimulus levels by the integtated spike discharges and by the ratings of the subject was compared using the P(A) measure of the Signal Detection Theory. It was found that both the neurophysiological and the psychophysical measurements provided about equal discrimination. 6. In addition it has been found that spike discharges and ratings share a common variance beyond their common dependence on the stimulus level. Among the factors contributing to this interdependence a 'temporal position effect' was the most significant. 7. In spite of this interdependence between discharge rates and subjective ratings, the latter gave a better estimation of the stimulus size than of the discharge rates of the individual C fibre under study. 8. It was concluded that the polymodal C-nociceptors might be instrumental for the quantitative aspects of heat pain sensation. The hypothesis was derived from the present results that, under the conditions of cour experiments, the loss of information in the course of central processing might be about equal to the gain by the parallel processing in a population of nociceptors excited by a stimulus.
The posterior nuclear complex of the thalamus in rhesus, pigtailed and squirrel monkeys consists of the combined suprageniculate‐limitans nucleus and an ill defined region of heterogeneous cell types extending anteriorly from the dorsal lobe of the medial geniculate body towards the posterior pole of the ventral nuclear complex. This region is referred to as the posterior nucleus.
The cortical projections of each of these nuclei, together with those of the adjacent ventral, pulvinar and medial geniculate complexes, have been studied by means of the autoradiographic tracing technique. The suprageniculate‐limitans nucleus, the main input to which is the superior colliculus, projects upon the granular insular area of the cortex. The medial portion of the posterior nucleus projects to the retroinsular field lying posterior to the second somatic sensory area. There is clinical and electrophysiological evidence to suggest that the retroinsular area may form part of a central pain pathway. The lateral portion of the posterior nucleus which is closely related to certain elements of the medial geniculate complex, projects to the postaditory cortical field. The ventroposterioinferior nucleus, which may be involved in vestibular function, projects to the dysgranular insular field.
The principal medial geniculate nucleus can be subdivided into a ventral division that projects to field AI of the auditory cortex and a dorsal division that merges with the posterior nucleus; it is further subdivided into an anterodorsal component that projects to two fields on the superior temporal gyrus, together with a posterodorsal component in which separate cell populations project to areas lying anterior and medial to AI. The magnocellular medial geniculate nucleus, sometimes considered a part of the posterior complex, appears to project diffusely to layer I of all the auditory fields.
The Auditory fields are bounded on three sides by the projection field of the medial nucleus of the pulvinar which also extends into the upper end of the lateral sulcus to bound the fields receiving fibers from the posterior nucleus. The topography of the areas receiving fibers from the posterior, medial geniculate and pulvinar complexes, taken in conjunction with the rotation of the primate temporal lobe, permits all of these fields to be compared with similar, better known areas in the cat brain.
There has been a long-standing controversy as to whether or not internal organs are innervated by a special category of 'visceral nociceptor'. Recent experimental studies on the afferent supply of some viscera have thrown new light on this issue by demonstrating the presence of several categories of visceral sensory receptor, including high-threshold receptors, 'silent' nociceptors and intensity-encoding receptors. Advances in the understanding of how the CNS processes nociceptive signals have also helped to clarify the issue. The authors of this report, originally having different points of view, present here a common and closer approach to the visceral nociceptor controversy.
We studied six patients who developed spontaneous hemibody pain following lesions of the parietal lobe. The pain was characterized as burning or icelike, and was associated with impairment of pin and temperature appreciation. Computed tomographic scanning showed that the common area of involvement in all cases was the white matter deep to both the caudal insula and the opercular region of the posterior parietal cortex. We suggest that disruption of the interconnections between these cerebral cortical areas (including the second somatosensory representation, SII) and the thalamus, particularly the intralaminar and ventroposterior nuclei, may be responsible for producing a thalamocortical disconnection syndrome with spontaneous pain as its clinical manifestation.
The reflex pressor response evoked by static muscular contraction is widely believed to be caused by the stimulation of group III and IV afferents. Although the specific nature of the contraction-induced stimulus to these thin-fiber afferents is unknown, they are thought to be stimulated in part by a condition arising from a mismatch between blood supply and demand in the exercising muscle. Hypoxia, a condition found in skeletal muscle during such a mismatch, may stimulate these afferents. We have therefore tested the hypothesis that perfusion of the triceps surae muscles with hypoxic blood stimulates group III and IV afferents in barbiturate-anesthetized cats. We found that 3-3.5 min of hypoxia with the triceps surae muscles at rest significantly (P < 0.05) increased the average discharge rate of contraction-sensitive group IV afferents but had no effect on the average discharge rate of contraction-sensitive group III afferents. Hypoxia had only trivial effects on the discharge of contraction-insensitive group III and IV afferents. Hypoxia stimulated 4 of 11 contraction-sensitive group IV afferents and 2 of 13 contraction-sensitive group III afferents. The responses of the afferents stimulated by hypoxia were small in magnitude. Hypoxia with the muscles at rest appeared to have no effect on either hydrogen or lactate ion concentrations in the femoral venous blood. In addition, hypoxia increased the responses to contraction in only 3 of 22 group III and 4 of 21 group IV afferents tested. We conclude that muscle tissue hypoxia is a minor stimulus to afferents that sense a mismatch between blood supply and demand during static contraction.