The Insular Cortex
& Social Emotions

The insular cortex grants you self awareness, empathy and social discipline. This article suggests that evolutionary history and the logic of combinatorial coding point to these specific functions for the insulae. As against this narrower demarcation of its functions, the insulae have been linked by researchers to a confusing spectrum of activities including “a role in emotions, including perception, motor control, self-awareness, cognitive functioning, and interpersonal experience.” Behavioral and encephalographic measurements, combined with functional imaging studies do link neural activity in the insulae to numerous brain functions. While the organ may appear to participate in many activities, its functions are limited.

The logic of intuition enables each neural organ in the nervous system to access a wide range of data, while performing specific roles. The historic development of specific neural subsystems and the logic of information flow support this conclusion. As an example, while the function of the olfactory system is to recognize smells, recognized smells do trigger innumerable upstream neural responses. In a similar manner, the pivotal function of the limbic system is to control the behavioral choices of the system. Many organs within the system participate in this process. Among them, the insular cortex specifically grants the mind self awareness, empathy and social discipline.

• Control systems of the human brain have evolved over millions of years.
• From a primitive sensitivity and response to touch, the system added sensitivity to more senses. The system responded to danger with fear and anger. At the highest level, it became capable of rational evaluation and finally to social responsible activity.
• The insular cortex has access to a whole range of bodily sensations.
• That sensitivity grants us the sense of self.
• Mirror neurons within the organ enable us to sense the feelings of others. By sharing pain and joy, the organ converted us into social beings.
• The organ generates a sense of disgust with socially unacceptable behavior.
• The organ motivates us to higher levels of behavior through pleasure and pain.

The Insular Cortex –An Evolving Control System
Evolution of the neural control systems delivered increasingly sophisticated evaluations and controls for animals to approach and consume, or to reject and escape. From just touch, the system proceeded to evaluate smell, taste, sound and vision to test the environment. Its motor movements learned to walk, run, fly or destroy opponents. Those movements became modulated to act with gentle care, or violent aggression. The system stored memories to respond to significant events. It learned to investigate. At the highest level, with the addition of the insular cortex, the system learned to cooperate with others and act for group benefit.

The Insular Cortex –A Landmark In The Limbic System
The insular cortex, which persuades you to be more sociable is a recent evolutionary development. The early reptiles lacked such systems and acted with ruthless self interest. Compassion and harmony entered the hitherto brutal world of animal interactions through the development of this amazing organ.

The organs within the limbic system (LS) provide a living record of the evolution of the control systems of the mind. The earliest controls responded to the touch sensation. For the primeval Hydra, a branched tubular animal, a simple net of neurons between its outside and its internal digestive cavity responded to any physical stimulus to any part of its body by contracting and expanding. With this process, the animal varied its length to move about and used its tentacles to push food particles into its mouth. Strong contractions expelled indigestible material from the same orifice. The animal could approach and consume, or reject and escape.

While the earliest control systems merely responded to the touch stimulus, addition of the olfactory system added the identification of smells to the decision making process. Vision, taste and sound added more criteria for making decisions. While the development of neurons in the spinal cord added more complex muscle movements for fish and animals, the more sophisticated controls developed higher up in the LS.

The hypothalamus, one of the earliest organs in LS, injected sequences of physical movements for specific behavioral responses. Such behaviors satisfy the objectives of the primitive emotions of pleasure, aversion, rage, satisfaction of hunger and thirst. As an example, stimulation of the lateral hypothalamus can induce simulated rage, including biting and attacks upon any moving object.

The amygdala, which appeared alongside, dispatches instructions to the hypothalamus. The organ remembers sensory signals indicating causes for fear, or anger. It has LTP circuits, which persist over long periods in their sensitivity to emotionally significant sensory signals. The amygdala reacts with jumpy emotional responses, bypassing the more elaborate pattern recognition circuits at higher levels.

The hippocampus was added to LS as the archival system for those significant events, which impact on the pleasure, aversion, rage, hunger and thirst events encountered by the animal. The organ remembers geographic locations and assists in the formation of long term memories for emotionally significant events.

The septal nuclei, another addition to LS, acts as a motivating tool to persuade the individual to follow favorable patterns of behavior. Electrical stimulation of the septal nuclei elicit feelings of pleasure in human subjects, giving them a “glowing feeling.” Rats will tirelessly press levers to receive such electrical stimulation, preferring self-stimulation over food.

While the lower level systems responded blindly to emotionally significant sensory signals, the prefrontal regions added a rational investigative capacity. Since investigation demanded conscious attention, the prefrontal regions contained powerful inhibitive circuits, which suppress the emotional turmoil generated by the organs in LS. When attention is consciously controlled, the prefrontal regions have the power to still the mind.

Functioning at the highest evolutionary level, the insular cortex uses several tools to enforce social discipline. With more durable memories for social events, the organ suppresses short term objectives of the amygdala to support enduring emotional attachments. As suggested by Damasio's "somatic marker" hypothesis, the organ triggers a range of positive and negative physical signals to heighten the impact of its instructions. The insula sends pain signals to the amygdala to enable avoidance of socially undesirable activities and pleasure signals to the septal nuclei to support socially rewarding behaviors. Mirror neurons within the organ further reinforce these signals by making the person actually experience the pain and joy of his fellow being.

The Insular Cortex – fMRI Evidence Fails To Differentiate
The insular cortex, first described by Johann Christian Reil, is a portion of the cerebral cortex folded deep within it. It is divided into a larger region in front and a smaller one at the rear. The front portion has powerful links to the amygdala and is considered to be a part of LS. More than a dozen field areas have been identified within the posterior insula.

Statistical derivations of the fMRI measurements of increases in the blood-oxygen-level dependence (BOLD) of the blood flow in cerebral arteries can pinpoint neural activity. Such reports suggest a role for the insular cortex in the recognition of smells, tastes and visceral responses. Its neurons are reported to be activated by sounds, touch, warmth and coldness. They are activated both by a distended stomach and a full bladder. They are activated by movements of the body; by pain, temperature, itch and changes in local oxygen status.

Such activation of neurons in the insulae merely imply that the organ has access to such data. These are the inputs to the insular cortex, similar to the combinatorial inputs to the olfactory bulb from olfactory receptors. The outputs from the olfactory bulb, which achieve its real function recognizing odors. If the bulb is damaged, the ability to recognize odors is lost. So also, the pivotal role of the insular cortex can only by identified by uncovering the functional deficits caused by damage to the organ.

The Insular Cortex –Self Awareness & Limb Ownership
The degeneration of the "Von Economo Neurons" (VENs), located in the anterior insular cortex is specifically associated with the loss of emotional awareness. Modern lesion analysis techniques in patients with damage to the insula and fMRI results in healthy subjects suggest a prominent role of the right insula for a sense of limb ownership as well as the awareness of bodily movement. As a single region, which ceaselessly senses the whole universe of bodily sensations, one function of the organ is to perceive bodily experiences as being related to those of a single self. Thickness of the right anterior insula has also been associated with people who meditate. Such people have greater awareness of body activities and of emotions, including the ability to time one's own heart beat.

The Insular Cortex –Empathy
John Allman identified within the anterior insular cortex a population of neurons, called spindle neurons, which are specific to great apes. At the highest level of evolution, these regions have contributed the ability to empathize to animals. They become active both while we experience bodily sensations and while we view the bodily experiences of others, which cause such sensations. When looking at images of painful events, the insula generates sensations of pain, as if those events were experienced personally. The insula also responds to the joyful experiences of others.

Shared pain and joy lead to cooperative living. Members of a community conform to social mores, because of a ceaseless awareness that individual action can cause pain or joy to others. The insular cortex disciplines you socially both by creating such awareness and by triggering inner warmth, or discomfort to modify social behavior. Damage to these regions cause a person to lose social skills.

The Insular Cortex –Disgust For Wrong Moral Choices
The insula recognizes patterns and triggers specific emotions. Researchers discovered that the organ is activated when you smell rotten food, or even if you taste such food. Science discovered (Nobel Prize 2004) that specific neuronal combinatorial codes fired by the olfactory system indicate recognition of specific odors. Similar code recognition processes also apply for tastes. Evidently, the insula recognizes such codes. The insula becomes activated with the smell, taste, touch or sight (biting into a live cockroach) of rotten food. On recognizing such signals, the insula sends signals to the hypothalamus, which sets off a bodily rejection cycle, which makes you want to “throw up.”

Just as it can recognize odors, the insula recognizes behavior patterns. The insula of a sensitive viewer will trigger disgust, if it were to witness the brutal killing of a helpless victim. Nerve impulses from the insula to the hypothalamus will trigger visceral reactions, nauseating the viewer. It is the insula, which developed in humans the capacity to be disgusted by moral failures. By creating such sensitivity in millions of people, the insular cortex plays a crucial role in strengthening the binding fabric of society.

The Insular Cortex –Sensations To Influence Decisions
The sensations experienced by the insula influence social decisions. Lawrence Williams asked volunteers to rate an individual from a brief personal description. The ratings were requested after the volunteers were made to hold warm or cold cups of coffee. The subjects who held the warm cups tended to rate the individual as having warmer personalities. In a similar experiment, those holding a warming pad acted more generously than those holding a cooling pad. Even “seat of the pants” experiments showed that people occupying soft seats tended to be less rigid in their ability to cooperate.

The neural responses of the insular cortex make you cringe in shame for unsocial behavior and stand tall for acts of selfless generosity. The wide range of physical signals triggered by the organ makes you aware night and day of the impact of your behavior on society.

This page was last updated on 31-Dec-2013