The insular cortex is a region of the brain tucked so deeply inside the lateral fissure that it remained largely overlooked for more than a century after its discovery. Sometimes called the “Island of Reil” after the anatomist who first described it, the insula sits hidden beneath folds of the frontal, parietal, and temporal lobes, invisible from the brain’s outer surface. Despite its concealment, the insula participates in an astonishing range of human experience, from the gut feeling that something is off, to the burn of a hot pan, to the craving for another cigarette. Researchers now consider it one of the most functionally diverse structures in the entire brain.
Hidden Anatomy
To see the insula, you would need to peel back the overhanging folds of cortex (called opercula) that cover it like a lid. Beneath them lies a wedge of cortical tissue divided by small grooves into multiple sub-regions. Depending on the technique used to map it, the insula can be carved into anywhere from two broad zones to as many as thirteen distinct subdivisions.1Europe PMC. Structure and Function of the Human Insula The simplest and most commonly used division splits it into two halves: a front (anterior) portion and a rear (posterior) portion. These two halves do not simply mirror each other. The posterior insula is more closely wired to sensory and motor areas and handles raw bodily signals like pain location and skin temperature. The anterior insula connects more heavily with emotional and cognitive circuits, blending those raw signals with context, memory, and feeling.2PubMed Central. The Role of the Insula in Chronic Pain and Associated Structural Changes: An Integrative Review This front-to-back gradient, from concrete sensation to abstract interpretation, is a recurring theme across nearly everything the insula does.
The Brain’s Traffic Controller
One of the most influential ideas about the insula is that it serves as a kind of traffic controller for the brain’s large-scale networks. At any given moment, your brain is toggling between outward-focused attention (reacting to something in the environment) and inward-focused thought (daydreaming, planning, self-reflection). These two modes are handled by separate circuits, often called the central-executive network and the default-mode network. The anterior insula, partnered with a strip of cortex called the anterior cingulate, forms what researchers have named the “salience network.” Its job is to flag events that matter, whether they come from outside or inside, and then flip the switch so the right network takes over.3PubMed Central. Saliency, switching, attention and control: a network model of insula function
This is not just a theoretical model. Brain-imaging work using a technique that tracks the timing and direction of neural signals found that the right anterior insula, specifically, plays a causal role in switching between these two networks. The pattern held across different types of tasks and even during rest, suggesting the insula is not merely reacting to stimuli but actively orchestrating which brain systems get priority.4PubMed Central. A critical role for the right fronto-insular cortex in switching between central-executive and default-mode networks If the salience network misfires, you might over-attend to irrelevant signals (a hallmark of anxiety) or fail to notice important ones (a problem in certain forms of brain injury). This switching function helps explain why the insula keeps showing up in studies of conditions as varied as chronic pain, addiction, and attention disorders.
Sensing the Body From the Inside
You know when your heart is pounding, when your stomach is upset, when you need to take a breath. That awareness of internal bodily states is called interoception, and the insula is its primary cortical home. Signals from the heart, lungs, gut, and other organs travel upward through the brainstem and thalamus and arrive first at the posterior insula, where they are registered in a relatively raw form: how fast, how strong, where exactly. The anterior insula then integrates those signals with predictions, emotions, and context, creating what amounts to a moment-by-moment model of how your body is doing.5PubMed Central. Anterior insular cortex and emotional awareness
This process has far-reaching consequences. Emotional awareness seems to depend on it: to feel afraid, your brain needs to register the racing heart and the tight chest, and the anterior insula is where that registration happens. One model proposes that the anterior insula is not just reading out body states passively but is constantly generating predictions about what the body should be feeling and then comparing those predictions against incoming data.6PubMed Central. Anterior insular cortex and emotional awareness When prediction and reality diverge, you get a conscious signal: surprise, discomfort, excitement. This “predictive interoception” framework helps explain everything from the butterflies-in-the-stomach feeling before a speech to why chronic pain patients sometimes feel pain out of proportion to their tissue damage.
Pain, Temperature, and Sensory Illusions
Pain processing in the brain does not live in a single spot, but the insula is one of its most critical nodes. Nociceptive input, the neural signals that encode tissue damage, arrives at the posterior insula, where the brain assesses pain intensity and location. From there, information flows forward to the anterior insula, which adds emotional color: how much the pain bothers you, how threatening it feels.7PubMed Central. The Role of the Insula in Chronic Pain and Associated Structural Changes: An Integrative Review This two-stage arrangement means that damage to different parts of the insula can produce very different outcomes. A lesion in the posterior insula might impair your ability to localize pain, while anterior insula damage could leave you able to detect pain but emotionally indifferent to it.
Temperature perception follows a similar path. Brain-imaging studies using PET scans found that graded cooling of the skin produced activity along the dorsal margin of the middle and posterior insula on the opposite side of the brain from the cooled hand.8PubMed. Thermosensory activation of insular cortex But the insula does not merely read out what temperature the skin actually is. In one memorable experiment, researchers produced the perceptual illusion of “paradoxical heat,” a situation where a person feels a burning sensation even though their skin is actually cool. A region of the right insula lit up specifically when participants experienced this phantom warmth, and the same region was suppressed during genuine mild cooling.9PubMed. Perceptual illusion of “paradoxical heat” engages the insular cortex The implication is striking: the insula appears to encode the perception of temperature rather than the physical temperature itself. It reports what you think you feel, not necessarily what is actually happening at the skin.
Disgust, Empathy, and the Emotional Mirror
If you have ever watched someone else bite into a rotten piece of food and felt your own stomach turn, the insula is a likely culprit. Disgust was one of the earliest emotions linked to the insular cortex, in part because the insula receives taste information and overlaps with regions that process nausea and visceral discomfort. But the story gets more interesting when it comes to shared experience. An imaging study showed that the same sites in the anterior insula that fire when a person tastes or smells something revolting also fire when the person simply watches another person’s face express disgust.10PubMed Central. The anatomy of empathy: Vicarious experience and disorders of social cognition The anterior insula is implicated in toxicity-related and disease-related forms of disgust, though its activation is not exclusive to disgust and whether it plays the same role in moral disgust remains debated.11NeuroImage: Clinical. Specifically altered brain responses to threat in generalized anxiety disorder relative to social anxiety disorder and panic disorder
This mirroring extends beyond disgust. A meta-analysis of empathy-for-pain studies found that the bilateral anterior insula and the anterior cingulate form a core network for pain empathy, and that these regions overlap with the areas activated during directly experienced pain.12PubMed. Meta-analytic evidence for common and distinct neural networks associated with directly experienced pain and empathy for pain In other words, watching someone stub their toe recruits some of the same insular circuitry as stubbing your own. Researchers have linked this overlap to the idea that the insula represents “global feeling states,” essentially a felt sense of what is happening, regardless of whether the experience belongs to you or someone you are observing. This mechanism likely contributes to the visceral, gut-level quality of empathy, as opposed to the more detached, cognitive kind.
Risk, Surprise, and Gut Decisions
The insula has become a key area of interest for researchers studying how people evaluate risk. During a simple gambling task in which risk levels changed constantly, the anterior insula showed activation that correlated with risk prediction error, meaning it responded more strongly when the actual risk of a gamble deviated from what a person expected. The timing of this response was fast enough to suggest the insula supports rapid updating of risk estimates as new information comes in.13PubMed Central. Human insula activation reflects risk prediction errors as well as risk
This sensitivity to surprise extends beyond financial gambles. When researchers tested both a gambling task and a perceptual task involving ambiguous visual stimuli, the anterior insula responded to uncertainty in both cases, suggesting it tracks surprise in a domain-general way, regardless of whether the uncertainty is about money or about what your eyes are seeing.14PubMed. Anterior insula reflects surprise in value-based decision-making and perception This fits with the salience-network framework: the insula flags anything that deviates from expectation, then helps recruit the brain resources needed to deal with it. The practical upshot is that the “gut feeling” people report when making risky decisions is not just metaphor. It likely involves actual visceral signals being processed through the insula and translated into an intuitive sense of whether something feels safe or dangerous.
Adolescents appear especially sensitive to this process. One longitudinal study found that weaker insular risk-processing in teenagers predicted increases in perceived stress over the following year. Among adolescents who also had poor cognitive control, this pattern went further, predicting increases in actual risk-taking behavior. Adolescents with good cognitive control, by contrast, were buffered from this effect even if their insular risk processing was low.15NeuroImage: Clinical. Specifically altered brain responses to threat in generalized anxiety disorder relative to social anxiety disorder and panic disorder
Addiction and the Urge That Disappears
One of the most dramatic demonstrations of insular function came from patients who suffered brain damage that included the insula. Researchers noticed that smokers whose strokes destroyed part of the insular cortex were far more likely than other brain-damaged smokers to quit immediately, effortlessly, and without relapse or lingering cravings.16PubMed Central. Damage to the insula disrupts addiction to cigarette smoking The urge simply vanished. This finding made headlines because it suggested the insula is where the conscious craving for cigarettes lives, not just a general addiction circuit but a specific substrate for the felt need to smoke.
Follow-up work refined the picture. Damage to the basal ganglia alone could also disrupt smoking addiction, but when basal ganglia damage was combined with insula damage, the disruption was stronger.17PubMed Central. Basal ganglia plus insula damage yields stronger disruption of smoking addiction than basal ganglia damage alone This suggests the insula does not act in isolation but works alongside reward-related structures to maintain the urge. The interoceptive angle matters here: craving is not just a thought but a body state, an itch-like physical pull, and the insula’s role in representing internal bodily sensations probably explains why its loss so profoundly deflates the desire to smoke. Researchers have speculated that targeted interventions aimed at insular activity, whether through brain stimulation or pharmacology, could someday help with addiction treatment, though that remains an active and early area of investigation.
Anxiety, Eating Disorders, and Psychiatric Relevance
Given its central role in interoception, emotion, and salience, it is not surprising that the insula shows up as abnormal across a range of psychiatric conditions. In anxiety disorders, the pattern is consistent: the insula tends to be overactive, especially the anterior portion, particularly in response to threatening or fear-inducing stimuli.18PubMed Central. Insular Cortex-Biology and Its Role in Psychiatric Disorders: A Narrative Review In one study of anxious individuals, heightened activity in the dorsal anterior insula correlated with higher anxiety proneness and with lower perceived control. The more the insula fired, the less control participants felt they had over potentially negative events.19Translational Psychiatry. Increased anterior insula activity in anxious individuals is linked to diminished perceived control
Different anxiety disorders may involve slightly different insular signatures. Patients with generalized anxiety disorder showed increased activity in the dorsal anterior insula that was specific to their diagnosis compared with patients with social anxiety or panic disorder. Meanwhile, a broader anterior insula response to threat was shared across all the anxiety groups.20NeuroImage: Clinical. Specifically altered brain responses to threat in generalized anxiety disorder relative to social anxiety disorder and panic disorder This hints that the insula is not a monolithic “anxiety switch” but rather a region whose different sub-zones may contribute to the distinct flavors of anxious experience, from the chronic worry of generalized anxiety to the acute dread of panic attacks.
Eating disorders show their own insular fingerprint, and it goes in opposite directions depending on the condition. Women who had recovered from anorexia nervosa showed a diminished anterior insula response to the taste of sugar compared with healthy controls, while women recovered from bulimia nervosa showed an elevated response. The insula appeared to encode the rewarding quality of sweet taste differently depending on the person’s history with food and eating.21PubMed Central. Altered insula response to sweet taste processing after recovery from anorexia and bulimia nervosa Because these differences persisted even after clinical recovery, they may reflect underlying vulnerabilities rather than consequences of the illness itself.
Von Economo Neurons and What They Suggest About Evolution
Buried within the front part of the insula is a peculiar type of nerve cell found nowhere else in the cortex outside one other region, the anterior cingulate. These are von Economo neurons, named for the anatomist who first noticed their unusual shape: large, spindle-like, with a simple elongated structure rather than the bushy branching of a typical cortical neuron. Their size and sparse branching suggest they are built for speed, rapidly relaying basic information to distant brain areas while their smaller, more elaborate neighbors send slower, more detailed messages.22PubMed Central. The von Economo neurons in the frontoinsular and anterior cingulate cortex
What makes these neurons especially intriguing is their evolutionary distribution. In primates, they are found only in great apes and humans, not in monkeys or other primates. But they also turn up in elephants and certain whale species, leading to early speculation that they might be a specialization tied to very large brains or complex social lives.23PubMed Central. The von Economo neurons in the frontoinsular and anterior cingulate cortex More recent work has complicated that story. When researchers used careful counting methods to survey the brains of bowhead whales, cows, sheep, deer, horses, pigs, and even rock hyraxes, they found von Economo neurons in every species examined, each with its own distribution patterns and densities. These are not all large-brained or famously social animals. The repeated emergence of these neurons in distantly related lineages looks more like convergent evolution, the independent development of a useful neural design, than a hallmark of any single trait like sociality or intelligence.24PubMed. An analysis of von Economo neurons in the cerebral cortex of cetaceans, artiodactyls, and perissodactyls
These neurons appear to be selectively vulnerable in certain diseases. In behavioral-variant frontotemporal dementia, a neurodegenerative condition that erodes personality and social behavior, von Economo neurons and a related cell type called fork cells are lost early and preferentially from the frontoinsular cortex. This selective loss does not occur in Alzheimer’s disease, where the insula is affected later and less specifically.25PubMed Central. Selective frontoinsular von Economo neuron and fork cell loss in early behavioral variant frontotemporal dementia The link between the destruction of these fast-conducting neurons and the collapse of empathy, self-awareness, and emotional regulation in frontotemporal dementia offers circumstantial but compelling evidence that von Economo neurons play a meaningful role in the insula’s higher-order functions.
Heart Rate, Blood Pressure, and Autonomic Control
The insula is not only a sensor of the body’s internal states but also an active regulator. Animal studies have shown that numbing the insula with a local anesthetic significantly depresses the baroreflex, the mechanism that keeps blood pressure stable when you stand up or exert yourself. The effect appears to operate through the parasympathetic branch of the autonomic nervous system, the “rest and digest” side, rather than the sympathetic “fight or flight” branch: blocking the insula reduced baroreflex sensitivity without changing levels of circulating stress hormones.26PubMed. Role of the insular cortex in the modulation of baroreflex sensitivity In clinical settings, strokes that damage the right insula have been associated with cardiac arrhythmias and sudden cardiac events, a connection that makes more sense once you appreciate the insula’s role in autonomic regulation. It is one of the brain regions where the nervous system and the cardiovascular system intersect most directly.
Speech and the Left Anterior Insula
The insula has long had a footnote in neurology textbooks thanks to its proximity to Broca’s area, the classical language region in the left frontal lobe. Lesion studies and brain imaging have since clarified that the left anterior insula contributes specifically to the motor aspects of speech production, particularly the planning and coordination of the complex muscle movements required for articulation.27PubMed Central. The role of the insula in speech and language processing Damage here can produce apraxia of speech, a condition where a person knows what they want to say but struggles to coordinate their lips, tongue, and jaw to say it. The words are not lost cognitively; the motor programs needed to produce them are disrupted.
This matters clinically for epilepsy surgery. Insular epilepsy is notoriously difficult to diagnose because seizures originating in the insula often mimic seizures from neighboring regions. A meta-analysis of surgery outcomes found that about two-thirds of patients who underwent insular resection were seizure-free at last follow-up. Temporary neurological complications, mostly motor deficits, occurred in a substantial proportion of patients, but permanent deficits were uncommon. Resections on the dominant hemisphere (typically the left, where language circuits live) were associated with transient language difficulties, though permanent language loss was very rare.28PubMed Central. Predictors of outcomes after surgery for medically intractable insular epilepsy: A systematic review and individual participant data meta-analysis
Placebo Effects and the Expectation Machine
If the insula tracks predictions about bodily states, it follows that it should be involved in placebo responses, situations where your expectation of relief actually changes what you feel. Research on placebo analgesia bears this out. In one study, participants who reported the greatest pain reduction under a placebo condition also showed the largest decreases in anterior insula and anterior cingulate activity during the painful stimulus. The placebo did not just change how participants talked about their pain; it changed the neural response in the regions that process it.29PubMed Central. Cortical and subcortical responses to high and low effective placebo treatments The insula, in this context, sits at the junction of expectation and sensation: it receives top-down predictions (“this cream will help”) and bottom-up signals (“the stimulus is still there”), and the resolution of that conflict shapes what you consciously experience. This mechanism is relevant well beyond clinical trials. Any time your expectations about your body change your actual experience, whether it is a sugar pill, a reassuring word from a doctor, or the placebo component baked into every genuine drug, the insula is part of the machinery making it happen.