Anterior Insular Cortex

the anterior insular cortex (AIC) contains interoceptive re-representations that substantialize (that is, provide the basis for) all subjective feelings from the body and perhaps emotional awareness, consistent with the essence of the James–Lange theory of emotion and Damasio's 'somatic marker' hypothesis.

Craig's foundational thesis positions the AIC as the cortical substrate that converts interoceptive signals into all subjective bodily and emotional feelings.

Craig, A. D., How Do You Feel — Now? The Anterior Insula and Human Awareness, 2009thesis

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All conditions in the body and brain are represented by feelings, or by nested sets of feelings, that can be compared and 'weighed' in the AIC in order to make decisions that guide behavior.

Craig argues that the AIC functions as a decision-making organ, providing a 'common currency' of homeostatic salience against which all bodily and behavioral options are evaluated.

Craig, A.D. Bud, How Do You Feel? An Interoceptive Moment with Your Neurobiological Self, 2014thesis

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the anterior insula as an integral hub in mediating dynamic interactions between other large-scale brain networks involved in externally oriented attention and internally oriented or self-related cognition.

Menon and Uddin reframe the AIC not primarily as a feeling-generator but as a network hub that orchestrates the switch between externally and internally directed cognitive systems.

Menon, Vinod, Saliency, switching, attention and control: a network model of insula function, 2010thesis

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Almost all recent imaging studies of emotion report joint activation of the AIC and the ACC in subjects experiencing emotional feelings, including maternal and romantic love, anger, fear, sadness, happiness, sexual arousal, disgust, aversion, unfairness, inequity, indignation, uncertainty, disbelief, social exclusion, trust, empathy, sculptural beauty.

Craig marshals convergent neuroimaging evidence that the AIC-ACC axis is activated across the full spectrum of human emotional experience, supporting its claim to a universal role in affective awareness.

Craig, A. D., How Do You Feel — Now? The Anterior Insula and Human Awareness, 2009thesis

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the SN, and the AI in particular, plays a critical and causal role in switching between the fronto-parietal CEN and the DMN across task paradigms and stimulus modalities.

Menon and Uddin assert that the AIC causally mediates the competitive relationship between the brain's two major cognitive networks, assigning it a control function beyond interoception.

Menon, Vinod, Saliency, switching, attention and control: a network model of insula function, 2010thesis

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the activation in the right anterior insula correlated with subjective ratings. The activation in the right anterior insula and neighboring orbitofrontal cortex was strongly correlated with subjective feelings of cool stimuli and only weakly correlated with the objective temperatures.

Craig presents PET evidence that right AIC activation tracks subjective experience rather than objective stimulus properties, empirically distinguishing it as a locus of phenomenal feeling.

Craig, A.D. Bud, How Do You Feel? An Interoceptive Moment with Your Neurobiological Self, 2014thesis

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It is understandably mystifying that a region of the ventrolateral prefrontal cortex (the anterior insular cortex (AIC)) and a region of the medial prefrontal cortex (the anterior cingulate cortex (ACC)) are co-active in so many behaviours, because such widely separated regions in the cortex generally have distinct roles.

Craig acknowledges the theoretical puzzle posed by the consistent AIC-ACC co-activation and proposes that von Economo neurons provide the fast interconnection required to integrate their respective sensory and motor limbic functions.

Craig, A. D., How Do You Feel — Now? The Anterior Insula and Human Awareness, 2009supporting

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VENs are the substrate for fast interconnections between the physically separated advanced limbic sensory (the AIC) and motor (the ACC) cortices... The loss of emotional awareness and self-conscious behaviours in patients with frontotemporal dementia that correlates with the degeneration of VENs.

Craig proposes that von Economo neurons, concentrated in the AIC, enable the rapid integration of emotional moments and that their degeneration explains the collapse of emotional awareness in frontotemporal dementia.

Craig, A. D., How Do You Feel — Now? The Anterior Insula and Human Awareness, 2009supporting

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anger was associated with activation in the right anterior insula and the orbitofrontal cortex... Sexual arousal elicited by erotic films was strongly correlated with right anterior insular activation. Subjective assessment of the trustworthiness of faces also activated right anterior insula.

Craig's 2002 review documents the right-lateralized dominance of AIC activation across a range of discrete emotional states, anchoring the concept of re-representation of interoceptive cortical images in subjective feeling.

Craig, A. D., How Do You Feel? Interoception: The Sense of the Physiological Condition of the Body, 2002supporting

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the right AI plays a critical and causal role in switching between two other major networks (the CEN and the DMN) known to demonstrate competitive interactions during cognitive information processing.

Menon and Uddin demonstrate through Granger causality analysis that the right AIC exerts directional, causal influence over the transitions between the brain's principal cognitive networks.

Menon, Vinod, Saliency, switching, attention and control: a network model of insula function, 2010supporting

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the evidence described in this section compels the idea that the bilateral AIC engenders awareness of feelings in the present moment — 'now.' These findings also fit the interpretation that awareness is a singular operation, as in, 'the mind's eye.'

Craig concludes that the bilateral AIC is the neural substrate for the phenomenal 'now' of conscious experience, equating its function with the classical philosophical concept of the unified present moment of awareness.

Craig, A.D. Bud, How Do You Feel? An Interoceptive Moment with Your Neurobiological Self, 2014supporting

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when someone experiences lust, there's a notable spike of activity in the anterior insular cortex. But when they experience romantic love, there's a spike of activity in the posterior insular cortex.

Burnett uses the lust-versus-love dissociation to illustrate the functional gradient within insular cortex, positioning the AIC as the site of self-focused emotional experience in contrast to the more other-directed posterior insula.

Burnett, Dean, The emotional brain lost and found in the science of, 2023supporting

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the AI plays a more prominent role in detection of salient stimuli, whereas the ACC plays a more prominent role in modulating responses in the sensory, motor, and association cortices.

Menon and Uddin parse the functional division of labor within the AIC-ACC dyad, assigning the AIC primary responsibility for salience detection and the ACC for effecting downstream sensory and motor modulation.

Menon, Vinod, Saliency, switching, attention and control: a network model of insula function, 2010supporting

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the anterior insula is important for translating emotional salience into activation of the cognitive control network to implement goal-directed behavior.

Paulus synthesizes Craig's and Menon's frameworks within addiction research, positioning the AIC as the translator between emotional salience signals and the cognitive machinery for goal-directed action.

Paulus, Martin P., Interoception and drug addiction, 2013supporting

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the AI is involved in transient detection of salient stimuli and initiating attentional control signals which are then sustained by the ACC and the ventrolateral and dorsolateral PFC.

Menon and Uddin distinguish their model from Dosenbach's by assigning the AIC a transient detection role rather than a role in stable task-mode maintenance, emphasizing its function as an alarm rather than a governor.

Menon, Vinod, Saliency, switching, attention and control: a network model of insula function, 2010supporting

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MT enhanced interoceptive representation in adjacent anterior insular cortex, a region more responsive toward exteroceptive than interoceptive signals prior to training.

Farb demonstrates that mindfulness-based stress reduction training recruits the AIC for interoceptive processing tasks it did not previously perform, indicating experience-dependent plasticity in its functional boundaries.

Farb, Norman A. S., Mindfulness meditation training alters cortical representations of interoceptive attentionsupporting

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In the model proposed by Craig, the subjective awareness of salient events is represented more anteriorly, whereas more sensory attributes are thought to be represented posteriorly (Craig 2002). However, we currently do not have a good understanding of how the posterior and anterior subdivisions of the insula interact.

Menon and Uddin acknowledge Craig's posterior-to-anterior gradient model while candidly noting that the mechanism of integration between insular subdivisions remains an open empirical question.

Menon, Vinod, Saliency, switching, attention and control: a network model of insula function, 2010supporting

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Interoceptive signaling via the insula is thought to be particularly important for the physiological instantiation of the impulsive system.

Paulus locates insular interoceptive signaling within Bechara's dual-system model of addiction, assigning it a role in amplifying the impulsive system's sensitivity to immediate rewards.

Paulus, Martin P., The role of interoception and alliesthesia in addiction, 2009supporting

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individuals with drug addiction have dysfunctions in brain systems that are important for interoceptive processing, which include, among others, the insular and the anterior cingulate cortices.

Paulus identifies the insular cortex — AIC prominently among its divisions — as a site of clinically significant interoceptive dysfunction in drug addiction, motivating a treatment-oriented research agenda.

Paulus, Martin P., Treatment approaches for interoceptive dysfunctions in drug addiction, 2013supporting

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AIC — anterior insular cortex ACC — anterior cingulate cortex

Craig's abbreviation glossary confirms the canonical paired status of AIC and ACC as the primary abbreviations structuring his theoretical framework throughout the monograph.

Craig, A.D. (Bud), How Do You Feel? An Interoceptive Moment with Your Neurobiological Self, 2015aside

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the functions of the posterior insula can be segregated from those of the AI, and that the posterior insula plays a greater role in regulating physiological reactivity and homeostatic states... given the expansion that the human AI has undergone, animal models have proven less useful in identifying core functions of the human AI.

Menon and Uddin assert the evolutionary distinctiveness of the human AIC, arguing that its expansion relative to animal homologues necessitates human-specific empirical and theoretical approaches.

Menon, Vinod, Saliency, switching, attention and control: a network model of insula function, 2010supporting

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stimulant users relative to comparison subjects adjusted their choices less as a function of different error rates... showed an altered activation pattern in the left insular and bilateral dorsolateral prefrontal cortex.

Paulus reports empirical evidence that stimulant users show attenuated left insular activation during error-rate processing, documenting a behaviorally relevant AIC dysfunction in substance use populations.

Paulus, Martin P., Reduced Behavioral and Neural Activation in Stimulant Users to Different Error Rates during Decision Makingaside

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the interoceptive projections to the fundus of all three of these sulci are morphological anchors of the human brain... embryological gyrification in anthropoid primate brains brings these three interoceptive processing regions as close together as possible.

Craig argues from cortical morphogenesis that the AIC's anatomical position as a gyrification anchor reflects deep evolutionary pressure to maximize the energy efficiency of homeostatic integration.

Craig, A.D. Bud, How Do You Feel? An Interoceptive Moment with Your Neurobiological Self, 2014aside

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activity in this area is inversely correlated in functional-imaging studies with the activation in the AIC that is associated with awareness and task-related attention... Recent clinical and anatomical correlations in patients with anosognosia for hemiplegia and hemianaesthesia have focused on the insula.

Craig documents the inverse relationship between default network activity and AIC-mediated awareness, and notes clinical evidence implicating the insula in anosognosia, further supporting the AIC's role in self-awareness.

Craig, A. D., How Do You Feel — Now? The Anterior Insula and Human Awareness, 2009aside

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