The insular cortex — that deeply folded expanse of cortex hidden within the lateral sulcus — occupies a position of remarkable theoretical density in the depth-psychology corpus. The dominant voice is A.D. (Bud) Craig, whose sustained programme of neuroanatomical research reconstitutes the insular cortex as the primary interoceptive cortex: the site where homeostatic sensory signals, ascending via lamina I spinothalamic neurons and the VMpo thalamic relay, are progressively integrated from posterior to anterior subdivisions, culminating in the anterior insular cortex (AIC) as the locus of subjective feeling, self-awareness, and the sense of the living body. Craig's posterior-to-anterior gradient model — in which primary interoceptive representation in the dorsal posterior insula gives way to re-represented, emotionally elaborated awareness in the AIC — structures the conceptual field. Menon and Uddin extend this framework into network neuroscience, positioning the anterior insula as a hub of the Salience Network, mediating detection and attentional prioritization of biologically significant events. Paulus deploys the insular cortex clinically, demonstrating its dysfunctional engagement in drug addiction and its key role in interoceptive prediction error. Burnett introduces an anterior/posterior dissociation between lust and romantic love. Across authors, a persistent tension runs between the insular cortex as a sensory relay and as a generator of conscious subjective states — making it the neurobiological fulcrum of debates over embodied emotion, self-awareness, and the somatic basis of feeling.
neurobiologist Bud Craig has identified an area deep inside the mammalian brain — the insular cortex — as the place where interoception, or the processing of bodily stimuli, generates feelings.
Craig's programmatic thesis: the insular cortex is the anatomical and functional locus at which interoceptive processing is transformed into subjective feeling.
, How Do You Feel? An Interoceptive Moment with Your Neurobiological Self, 2015thesis
Basically all agree that the posterior half differs from the anterior half and that the insular cortex is different on the right and left sides of the brain, at minimum.
Craig synthesizes fMRI and neuroanatomical evidence to establish that the insular cortex is functionally and structurally heterogeneous along both the anteroposterior and left-right axes.
, How Do You Feel? An Interoceptive Moment with Your Neurobiological Self, 2014thesis
several studies reported that specific nociceptive activation in the dorsal posterior insular cortex of humans is somatotopically organized along an anteroposterior gradient.
Craig documents that the dorsal posterior insular cortex constitutes a primary nociceptive cortex with somatotopic organization, differentiating it from neighboring S2 areas.
, How Do You Feel? An Interoceptive Moment with Your Neurobiological Self, 2014thesis
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 anterior insular cortex as a network hub within the Salience Network, orchestrating switches between externally and internally directed cognitive modes.
, Saliency, switching, attention and control: a network model of insula function, 2010thesis
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.
Craig marshals the breadth of neuroimaging evidence to establish the anterior insular cortex as a universal substrate for the subjective experience of emotion.
, How Do You Feel — Now? The Anterior Insula and Human Awareness, 2009thesis
Figure 10 / Plate 6. The organization of the insular cortex in the monkey and the human. 149 Figure 11 / Plate 7. The anteroposterior somatotopic organization of laser-evoked potentials (LEPs) in the macaque monkey.
Craig's figure sequence maps the comparative neuroanatomical and somatotopic organization of the insular cortex across primate species, grounding the interoceptive gradient model anatomically.
, How Do You Feel? An Interoceptive Moment with Your Neurobiological Self, 2015supporting
the posterior insula plays a greater role in regulating physiological reactivity and homeostatic states. On the other hand, given the expansion that the human AI has undergone, animal models have proven less useful in identifying core functions of the human AI.
Menon distinguishes posterior insular functions in homeostatic regulation from the uniquely expanded anterior insula in humans, arguing for the limits of animal models in understanding human insular cortex.
, Saliency, switching, attention and control: a network model of insula function, 2010supporting
the middle insula, where activation associated with subjectively experienced affective bodily feelings first appears … the integration of exteroceptive activity … and the integration of homeostatic motor activity.
Craig identifies the middle insula as the emergent zone where subjective affective bodily feelings first appear through the integration of exteroceptive and homeostatic motor signals.
, How Do You Feel? An Interoceptive Moment with Your Neurobiological Self, 2015supporting
PLATE 14 (Figure 18). The role of insular cortex in subjective time estimation.
Craig identifies the insular cortex as a substrate for subjective time estimation within his cinemascopic model of awareness, extending its functional role beyond interoception.
, How Do You Feel? An Interoceptive Moment with Your Neurobiological Self, 2014supporting
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 applies the anterior/posterior insular dissociation to differentiate the neural substrates of lust and romantic love, illustrating the functional heterogeneity of the insular cortex.
, The emotional brain lost and found in the science of, 2023supporting
the AI and ACC form the core of a SN that facilitates the detection of important environmental stimuli … the SN, and the AI in particular, plays a critical and causal role in switching between the fronto-parietal CEN and the DMN.
Menon argues that the anterior insula plays a causal role in network switching between the Central Executive Network and Default Mode Network, constituting the core of the Salience Network.
, Saliency, switching, attention and control: a network model of insula function, 2010supporting
the insular cortex in rats might support crude affective feelings, at least feelings that represent smell, taste, and general conditions of the homeostatic sensorimotor system, feelings that are colored with positive (appetitive) or negative (aversive) hedonic valence.
Craig extends the concept of graded sentience to rat insular cortex, proposing that it supports rudimentary affective feelings tied to gustatory, olfactory, and hedonic valence signals.
, How Do You Feel? An Interoceptive Moment with Your Neurobiological Self, 2014supporting
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 establishes insular cortex dysfunction as a core neurobiological feature of drug addiction, framing it within a broader interoceptive processing deficit.
, Treatment approaches for interoceptive dysfunctions in drug addiction, 2013supporting
These afferents converge via several midway and thalamic way stations to the sensory cortex and the posterior insular cortex to provide a sense of the current body state.
Paulus maps the ascending interoceptive pathway to the posterior insular cortex as the site of current body-state representation, integrating Craig's neuroanatomical model into an addiction framework.
, The role of interoception and alliesthesia in addiction, 2009supporting
insular activation have been reported in aversive cue and context conditioning … insular cortex can be considered part of the network underlying fear conditioning.
Paulus positions insular cortex as a central node in fear conditioning circuitry, alongside the amygdala and anterior cingulate cortex, with direct relevance to addiction-related aversive learning.
, Interoception and drug addiction, 2013supporting
insular activation have been reported in aversive cue and context conditioning … insular cortex can be considered part of the network underlying fear conditioning.
Paulus reiterates the insular cortex's role in fear conditioning circuitry across drug addiction contexts, reinforcing its function in aversive associative learning.
, Interoception and drug addiction, 2014supporting
stimulant users … showed an altered activation pattern in the left insular and bilateral dorsolateral prefrontal cortex, but not the anterior cingulate, as a function of error rate.
Paulus demonstrates that stimulant users exhibit selective dysfunction in left insular activation during error-rate-dependent decision-making, dissociating it from anterior cingulate contributions.
, Reduced Behavioral and Neural Activation in Stimulant Users to Different Error Rates during Decision Makingsupporting
Interoceptive signaling via the insula is thought to be particularly important for the physiological instantiation of the impulsive system.
Paulus, drawing on Bechara's dual-system model, positions interoceptive insular signaling as the physiological substrate of the impulsive reward-seeking system in addiction.
, The role of interoception and alliesthesia in addiction, 2009supporting
the majority of the human insula likely has no equivalent in the rat or monkey … much of the recent critical thinking of insula function in humans has focused on its key role in the experience of emotion derived from information about bodily states.
Menon underscores the evolutionary uniqueness of the human insula and its centrality to embodied emotional experience, anchoring the network model in comparative neuroanatomy.
, Saliency, switching, attention and control: a network model of insula function, 2010supporting
the posterior, mid, and anterior insular cortices have different patterns of connectivity with other brain regions … the subjective awareness of salient events is represented more anteriorly, whereas more sensory attributes are thought to be represented posteriorly.
Menon maps differential connectivity patterns across the posterior-to-anterior insular gradient, aligning Craig's representational hierarchy with functional network architecture.
, Saliency, switching, attention and control: a network model of insula function, 2010supporting
the AI helps to generate control signals involved in 'stable maintenance of task mode and strategy' … the AI is involved in transient detection of salient stimuli and initiating attentional control signals.
Menon clarifies his model's distinction from Dosenbach's stable-maintenance account, positioning the anterior insula as a generator of transient salience-triggered attentional control signals.
, Saliency, switching, attention and control: a network model of insula function, 2010supporting
The insula is unique in that it is situated at the interface of the cognitive, homeostatic, and affective systems of the human brain, providing a link between stimulus-driven processing and brain regions involved in monitoring the internal milieu.
Menon articulates the insular cortex's unique anatomical and functional position at the intersection of cognitive, homeostatic, and affective processing systems.
, Saliency, switching, attention and control: a network model of insula function, 2010supporting
anatomically the AIC is not fully interconnected for some years … mirror self-recognition generally does not occur until eighteen months of age.
Craig introduces a developmental caveat regarding the AIC's structural maturation, linking the emergence of self-awareness to the progressive interconnection of anterior insular cortex in infancy.
, How Do You Feel? An Interoceptive Moment with Your Neurobiological Self, 2015aside
AIC — anterior insular cortex ACC — anterior cingulate cortex
Craig's abbreviation list establishes the terminological conventions used throughout his treatment of insular cortex function, pairing AIC consistently with ACC as the core control network.
, How Do You Feel? An Interoceptive Moment with Your Neurobiological Self, 2015aside
Safety signals mitigate the consequences of uncontrollable stress via a circuit involving the sensory insular cortex and bed nucleus of the stria terminalis.
A cited reference introduces the sensory insular cortex as a node in a stress-mitigating safety signal circuit in conjunction with the bed nucleus of the stria terminalis.
, How Do You Feel? An Interoceptive Moment with Your Neurobiological Self, 2015aside