Insula

Situated deeply in the lateral sulcus or Sylvian fissure of the human brain, the insula (also: insular cortex or insular lobe) is the top layer of the cerebrum.

The insula’s primary functions are the regulation and control of the physical and chemical conditions needed for the optimal functioning of the human body. It also plays a part in consciousness, by regulating a vast array of processes dealing with emotions.

Probably the most notable function of the insula is the assignment of emotional meaning to the physiological sensations and events. For example, if we feel any kind of physical pain, the insula would recognize it as a negative feeling. This makes the insula of great importance for psychopathology.

 

Anatomy and Structure of the Insula

The insula is a part of the cerebral cortex of the human brain. Located in the Sylvian fissure, it lies below the frontal, parietal, and temporal lobes of the brain.

The insula is divided into two different regions by the central insular sulcus. Those are the large anterior insula, and the small posterior insula. Surrounded by the circular cortex, the insula is covered and protected by the insular opercula – a cortical structure that functions as a cover over the lobes in both brain hemispheres and the insula.

Together with the limbic system, these structures comprise the emotional network which is in charge of processing the reception of sensory stimuli, as well as conscious feelings.

 

Which Brain Structures Does the Insula Connect To?

The insula comprises of an extensive network of both cortical and subcortical regions of the brain:

 

 

The cells of these regions project their axons to the thalamus, thus receiving auditory, somatosensory, olfactory, gustatory, and visual information.

None of these regions processes only one type of sensory information. Rather than that, they all function as an integrated system for the regulation and translation of sensory stimuli in the brain.

 

What Are the Functions of the Insula?

The insula processes some of the most vital cognitive functions and social emotions in the human brain, such as disgust, pride, humiliation, guilt, atonement. By this, it predicts the internal condition of the most vital systems of the body.

To add, this part of the human brain regulates heartbeat, blood pressure, body temperature, as well as both positive and negative emotions (including fear, anxiety, sadness, surprise), and assigns them to an image, sound, words, or event, thus prognosticating our future behavior.

 

What is Interoception?

Interoception is the most distinguished function of the insula. It’s the ‘gut’ sense which helps us understand what is going on with our body. Namely, it uses the information gained from the receptor cells of the sensory organs and translates them into corresponding feelings in order to regulate the vital functions of the body.

The interoception as a process is conducted by the insula, cingulate cortex, striatum, as well as the prefrontal cortex. Physiologically, it is involved in the gastrointestinal system, cardiorespiratory system, thermoregulatory system, in the processes that regulate the sensation of pain, as well as the immune and endocrine system.

The interoceptive data is transmitted through a large number of neural pathways that relay those sensations to be encoded in the processing area of the cerebral cortex. In this way, the brain is able to translate and predict the internal state of the body.

 

The Insula and Self-Awareness

Being aware of your personal traits, abilities, behaviors, and feelings, is a result of the function of the insula, together with the anterior cingulate cortex, as well as the medial prefrontal cortex.

The insular cortex is involved in a broad range of human behaviors, such as cravings, insights, and maternal love, for example, all based on the process of interoception.

Self-awareness is created by the consolidation of the multisensory data derived through the process of interoception via a strong network of neural pathways, which are later integrated and processed in the insular cortex.

 

What Happens if the Insula Suffers Damage?

This small part of the brain, the insula, supports the vitally important processes of hunger regulation, addictions, and cravings. Also, it’s the insula that makes us reach for one more piece of cake when we’re already full or one more cigarette.

When it suffers damage, the insula becomes dysfunctional and increases our inclination toward addictive substances, such as alcohol, drugs, stress, eating disorders, as well as the anxiety that accompanies them.

Misinterpretation of the signals sent through interoception or wrongful prediction of the internal state of our body leads to the discovery of underlying mental problems or anxiety disorders, such as:

 

 

  • Depression
  • Anorexia nervosa
  • Apathy
  • Obsessive-compulsive behaviors
  • Aphasia (Loss of ability to communicate fluently)

 

 

  • Various addictions

 

 

Anxiety Disorders

Anxiety is a psychological state of constant unrest, during which the body is highly alert and constantly expecting danger in order to activate the fight or flight response.

Tension, nervousness, feelings of panic and danger, as well as dread, are all symptoms of anxiety disorders.

 

Depression

A mood disorder that is characterized by a long-lasting feeling of sadness, which inhibits the progress of the affected individual. This emotional state gives rise to the feeling of low self-worth and guilt, thus reducing the ability of the individual to live life to the fullest.

It typically starts by failing to achieve a plan, after which the emotional needs of the individual fail to be met, after a severely traumatic experience, or after medical conditions that can change the functionality of the brain.

 

Obsessive-Compulsive Disorder (OCD)

A chronic and long-lasting anxiety disorder which occurs as a result of a dysfunctional part of the brain.

There are 4 types of obsessive-compulsive disorders, based on the gravity of the symptoms. All 4 types of disorders include both an obsession and a compulsion:

  • Contamination & Washing – The symptoms include excessive worrying about hygiene, feelings of disgust caused by surfaces and items which are not perfectly clean, obsessive washing and cleaning.

Individuals affected with this type of obsessive-compulsive disorder avoid all public places (especially public toilets) and obsessively try to clean themselves and their environment by using a lot of disinfecting and sterilizing solutions.

They tend to clean everything they come into contact with, and if they fail to do it impeccably, these individuals become overwhelmed by feelings of disgust, dread, and fear of infection.

 

 

  • Accidental Harm Doubts & Checking – The individuals who suffer from this type of obsessive-compulsive disorder are paralyzed with worries and fear of accidentally hurting someone, for instance, while driving or if they fear they’ve left the iron on, thus causing a fire that could hurt the ones living with them.

 

 

They are labeled as ‘checkers’, because they are obsessively checking the safety of their surroundings in order to prevent any accidental harm.

 

  • Just Right OCD: Symmetry, Arranging, & Counting – Perfectionism is the keyword for this obsessive-compulsive disorder. These individuals follow a compulsive pattern of behavior that includes constant and repetitive arranging and rearranging of the items that surround them, arranging and aligning everything to be in a perfect position (paintings, mirrors, desks, decorations, etc).

 

 

This behavior is very often accompanied by fears that if they don’t rearrange some items to the perfect symmetry, or make something appear ‘just right’, something bad would happen to them or their close ones.

  • Unacceptable Taboo Thoughts & Mental Rituals – This type of obsessive-compulsive disorder includes deep continuous thinking about the same negative, dark, or sad issue, which can be extremely harmful to the mental health of the individual. Very often, these individuals are obsessed with religious, sexual, or violent themes and occurrences.

These individuals usually hold the belief that their thoughts are dangerous, so they are trying their best to suppress and control them by engaging in excessive praying, analysis, seeking approval from the others, etc.

 

Anorexia Nervosa

Anorexia Nervosa is a neurological eating disorder that occurs as a result of structural changes in the insula. It affects both the brain and the body, and is characterized by an unexplainable fear of weight gain, as well as an abnormally low body mass index.

 

Apathy

Apathy is a syndrome of a neuro-cognitive disorder which partially results from atrophy of the left side of the insula. In fact, any kind of damage to the part of the brain which controls emotions and motivation can trigger a lack of self-worth, motivation, purpose, as well as a general absence of interest in all aspects of life.

 

Panic Disorder

This type of anxiety disorder characterizes sudden feelings of fear, although there is no realistically supported reason for that. The affected individuals feel like they’re losing control over a given situation, which triggers reactions like increased heartbeat, intense sweating, difficulty in breathing, or a feeling of numbness of the extremities.

 

The panic attacks occur with no prior warning and inhibit the freedom of living and movement of the affected individual. In order to avoid the stressful panic attacks, this individual often stays confined in a safe place, such as their home, avoiding any interaction with other people or situations.

 

 

To Sum Up

The insula is the part of the brain which is the most active in processing emotions, such as feelings of empathy for others, and decisions.

In addition, the insula translates the joke we hear from our friends as a funny and joyful moment, defines a hit as an assault, and decides to react upon that, and determines how much chocolate we need in order to satisfy our ‘sweet tooth’.

The mind and body are both controlled by the insula. If this part of the brain becomes dysfunctional, the body will suffer too. Such is the case with anorexia nervosa, in which the patients lose their weight up to a critical condition due to brain lesions or damage.

 

Fun Facts

Did you know?

 

  • Antonio Damasio is a neuroscientist of Portuguese-American origin who discovered the role of the insula in social cognition, as well as the fact that emotions play a vital role in decision-making.
  • Insula means an island in Latin. The other less familiar names dedicated to this part of the brain are The Island of Reil and The Hidden Fifth Lobe.
  • For a long time, the insula was one of the most neglected and mysterious parts of the brain, but eventually, it turned out that it performs some of the most vital cognitive functions.
  • Interoceptive avoidance occurs due to a traumatic event. As an example, if an individual experiences choking, the person would avoid everything that needs to be put around the neck: high-neck sweaters, necklaces, etc.
  • The sensory information received from a soft touch on the skin is one of the most frequently processed data by the interoceptive system in the brain. Namely, the soft touch activates the insula instead of the somatosensory cortex and is correlated with pleasantness, thermoregulation, and the prediction of pain by the sensory processing areas of the brain.
  • How many times have you stubbed your little toe on the coffee table or the door? It hurts, right? Well, the insula is the part of the brain that supports this sensory perception and helps you realize that the impact you feel is pain.
  • ‘Ego’ is the Latin word for the sense of self, regulated by the insula.
  • The love of a mother is one of the aspects of human behavior that is regulated by the insular cortex.
  • The insular cortex supports our ability to analyze our emotions and the behaviors resulting from them, which adds a philosophical touch to its function.
  • Without the proper functioning of the insula, we wouldn’t be able to feel happiness and joy.