Did you know that there is a “hidden lobe” in the brain that is not well known by many mental health professionals, yet serves one of the most critical functions in the experiencing of one’s own emotional state of being?
The vital role this lobe plays in people’s experiences of life is described in this brief passage from a psychiatry textbook published in 2022, where it was given just a few sentences in a 1145-page volume:
“The brain has no sensation; humans feel emotion only in their bodies. The insula helps to bring these visceral feelings into consciousness: The pain in one’s heart of grief, the warmth in one’s heart of love, and the tightness in one’s gut from fear all make their way into consciousness through the insula.” ¹
In this next article, I will highlight how the insula went from relative obscurity to a starring role in what it feels like to be human and what that may mean for psychiatric treatment in the future.
The insulae (plural because there are two, one on each side of the brain) are part of the limbic system located in the brain between the amygdala and the frontal lobe. Because insulae are folded and tucked deep within the brain, their function has long been neglected in research and was mistakenly defined as a primitive segment involved only in basic animal functions like eating and sex. It took the invention of modern brain imaging techniques like functional magnetic resonance imaging (fMRI) to be able watch insulae in action. What has been observed in brain scans is that each insula “lights up” when people being studied crave something, feel pain or even anticipate it, empathize with others, listen to jokes or music, see disgust on someone’s face, are shunned in a social setting, decide to not buy an item, see someone cheating, feel punitive, and even reflect the degrees of preference for eating chocolate. What has emerged is new recognition that the insula’s role is crucial to the conscious experience of what it feels like to be human. Moreover, in studies of brain disorders that are marked by lack of emotional awareness and regulation, such as autism and schizophrenia, the insulae show deficits in mechanisms of interoceptive awareness. And in disorders that have exaggerated reactions, such as anxiety and panic, the insulae are overactive and producing a misinterpretation of bodily sensations as being “dangerous” or “catastrophic”.
The term interoceptive awareness (or interoception) refers to the perception of the internal physiological state of the body, including sensations such as temperature, thirst, fatigue, feeling jittery, sexual arousal, and so on. Each insula functions like a receiving zone that reads what the nervous system reports about the state of the entire body and then generates subjective feelings that make the person feel inclined toward actions that keep things in a state of balance. These actions can be as basic as feeling inclined to eat when hungry or as complex as choosing to negotiate a better agreement with someone. In essence, the insulae answer the question “What do I need?” on an elemental level, and this serves the brain’s overall goal of sustaining homeostasis and the balance of energy expenditure. Of course, like every brain structure, insulae do not act alone but are part of multiple full-body physical and neurological circuits. Insulae receive information from sensory receptors in the skin and internal organs via nerve cells that specialize in communicating the variety of physical sensations, including heat, cold, itch, pain, taste, hunger, thirst, muscle ache, visceral sensations, and so-called air hunger (the need to breathe). The information is carried from the receptors along distinct peripheral and spinal pathways, into the brain stem, and then up to the posterior insulae in the higher brain (aka the “cerebral cortex”).
Different from most other animals, humans have evolved two innovations to their insulae that took this system of reading internal states to a new level. One involves the pathways of the circuitry; and information about the state of being in a human includes additional signals from the gut, heart, lungs, and other internal organs, not just from the site of the stimuli. The human brain then adds a step by sending all the information gathered to the front part of the insulae, particularly the right insula. It is in the frontal insulae that the symphony of body states and sensations are organized into emotional and social experience. In other words, this is where a bad taste or smell will be translated into a reaction of disgust, or a caring touch from a loved one gets translated into the experience of delight or comfort. The frontal insula is where people “sense” love and hate, gratitude and resentment, self-confidence and embarrassment, trust and distrust, empathy and contempt, approval and disdain, pride and humiliation, truthfulness and deception, atonement and guilt, etcetera.
The second major modification to the insulae is a type of cell found in only humans, great apes, whales, and possibly elephants. Called “spindle cells” or “von Economo neurons” (named for the scientist who first described them in 1925), these large, cigar-shaped cells appear to be central to the governance of social emotions and moral judgment. “Social emotions” are emotions like shame, envy, or empathy that depend upon one’s perception of the thoughts, feelings, or actions of another. Thus, the von Economo neurons help a human with the sensing and recognition of the emotions of others, and contribute to the complexity of social discernment.
The importance of insula function in influencing how a person experiences life makes it an ideal target for many kinds of treatment, though the practical applications for treatment in mental healthcare settings are still being developed. Nonetheless, research already verifies that mindfulness practices are beneficial. Methods such as meditation and self-reflection, which help you allocate more awareness to interoception of your internal states and less to thinking that merely evaluates the emotions mentally, have been shown to reduce the intensity of negative emotions and improve their regulation. This suggests that such approaches bring measurable changes to the brain by strengthening insula connectivity and function.
¹ Boland, Robert and Verduin, Marcia eds. Kaplan and Sadock’s Synopsis of Psychiatry, 12th edition. Wolters Kluwer, 2022: 1037.