anorexia, bulimia, BDD, meditation - whassup in/on the body? - the neuroscience

Manos Tsakiris
University of London

A critically-important ability, interoception, the sense of the internal physiological state of the body including awareness of  emotions, pain, pleasure, thirst, hunger, body temperature, tiredness, etc., is vital for meditation/spiritual practice.  


It is also important in dealing with anorexia nervosa, bulimia nervosa, and body dysmorphic disorder (BDD) in which folk cannot stop thinking, or obsessing about minor or imaginary defects in their physical features/appearance.  These are critical societal problems as almost half of adolescent girls report being dissatisfied with their appearance and 5% of Americans suffer from some type of eating disorder.

Insula(r) cortex

There is now a lot of research on how interoception works and what parts of the brain are involved in it.  Obviously, we have sensory receptors on our skin, in our muscles and internal organs.   All of this information is sent to an unusual region of the brain called the insula/insular cortex, which is nestled in a deep fold in the brain's external layer close to the ears.  


As the insula processes this information, it gives an ongoing awareness of our internal state of the body and hence, our "self-awareness" and emotional state.  At the same time, it combines this information with external information about what's happening with the body.  This gives us the ability to relate the results of external events, like the sharp pain of being cut with a piece of glass with the appearance of blood on our finger.  This integration of the information provides an ongoing body image or "what we think we look like" as Manos Tsakiris of the University of London calls it.   


The more developed our ability to integrate this information, the better our body image.  As Tsakiris points out, a runner with poor interoception may focus on how she imagines observers perceive her body as looking; is she too heavy, out-of-shape, or not as attractive as the runner next to her.  A runner with good interoception will focus instead on how her body is functioning while she is running; is her heart rate steady, are her feet blistering, is she out of breath, straining, or tired.  


With poor interoception, she focuses on mental images; with good interoception, she focuses on the feelings of/in her body and feels good about her body, no matter what its proportions are.

Hugo Critchley
University of Sussex

Interestingly, you can measure, for yourself, for free, just how interoceptive you are.  All you need is a stopwatch and a calculator.  Hugo Critchley and his team at the University of Sussex in England developed a reliable process for evaluating your "sense of self".  The process is simple:


       1.  After sitting comfortably for a few breaths, count your heartbeats for a minute just by feeling your heart's rhythm.  Do not use your wrist or neck, just your "internal sense" of your heart's beating. 

      2.  Then take your pulse for a minute by putting your fingers on your wrist or neck.


     3.  Wait for 2 minutes and then repeat steps 1 and 2; average your results for each step.


     4.  Determine the difference between steps 1 and 2; it doesn't matter whether it is + or -.   Divide this number by the result in step 2.  Subtract it from 1.


       As an equation this is:


               Interior sense of self = 1 - (Step 1 - Step 2)/Step 2


Your interoceptive ability is very good if you score 0.8 or higher; good if it is 0.6 to 0.8; poor if it is below 0.6.  Interestingly, this simple measure correlates highly with questionnaires and brain scans of insula activity; the score really does matter.


Christine Peat and Jennifer Muehlenkamp in a 2011 paper demonstrated that college-age women with problems from social anxiety to severe eating disorders scored lower on these interoceptive measures than those who were more in tune with their bodies.  A study by Olga Polatos published this spring found that anorexic women scored 0.68 in this test compared to a control group w/o an eating disorder who scored 0.77.  Two different fMRI studies on post-anorexic women showed decreased blood flow in the insula compared to controls w/o eating disorders. 


Most women's insulas respond positively with increased activation when looking at a picture of themselves, enhancing their experience of what it is like to be inside their own bodies.  


However, Perminder Sachdev and his colleagues at U of New South Wales in Neuropsychologia, Vol. 46, No. 8, Mar 2008, found that anorexic women showed no such increase, i.e. their insula was "mute" to the experience.  When looking at pictures of other folk, in both groups, the insula was "quiet".   (Men seldom have eating disorders of these types, which is why there are no studies on them - they have other problems.)


Manos Tsakiris,  Ana Tajadura-Jimenez and Marcell Constantini in their article "Just a heartbeat away from one's body: interoceptive sensitivity predicts malleability of body-representations" in the Proceedings of the Royal Society B, Vol   278, pp 2470-2476, Aug. 22, 2011 tested the effects of interoception on the "rubber hand" illusion.  There is an excellent BBC youTube video by Lawrence Rosenblum from UC Riverside demonstrating the illusion.


Tsakiris and his team tested 46 female college students - half with interoception scores over 0.80, the other half with scores below 0.50.  Those with lower scores could more easily be fooled into thinking the rubber hand was part of their body as they had weaker senses of their internal, "real", selves.


These differences extend to meditation.  The seminal study in 2007 by Farb, et al. on "Attending to the present: mindfulness meditation reveals distinct neural modes of self-reference", covered in an earlier blog, demonstrated a significant difference in the activation of the insula after two months of mindfulness meditation, 45 minutes/day.    

 In a), the posterior cingulate cortex (PCC) and the ventral medial prefrontal cortex (VMPFC), network which produces the "blah, blah, blah" self-referential thought process, remained active for the non-meditating controls.  


For the meditators, these centers are deactivated during meditation, and several new centers are activated, as shown in b), the lateral prefrontal cortex and the insula.  This produces the "now, now, now" network which replaces the "blah, blah, blah" network.


This is shown in these correlation charts for the "novice" controls on the left in  which there is strong correlation between the "blah, blah, blah" VMPFC and the right insula and no correlation between the "now, now, now" LPFC center and the insula. 


In the meditation-trained (MT) group on the right, the correlation between the "blah, blah, blah" VPMFC and the right insula has been broken, and replaced by a strong correlation with the "now, now, now" LPFC.      


So, our insula, the key to our interoceptive sense, the integrated "feeling" of our sense of self, is critical in determining whether we develop eating disorders, have a good feeling about "ourself", and how successful our meditation practice will be at reducing the "blah, blah, blah" and replacing it with "now, now, now".