Wednesday, October 13, 2010

The Brain Insula: Function and Disease

Nature Reviews Neuroscience is a scientific journal dedicated to neuroscience topics that recently celebrated it’s ten year anniversary.  To commemorate the accomplishment, the most highly cited articles from each of the last 10 years was identified.  This method provides a good proxy for the most important publication each year.  The 2009 most cited article was Dr. A.D. Craig’s article entitled: “How do you feel—now? The anterior insula and human awareness”.

Dr. Craig’s article highlights the converging fields of knowledge about the brain cortex region known as the insula.  This region lays hidden inside the brain in close proximity to the anterior cingulate gyrus (ACC).  The ACC is receiving increased attention as an important area for emotional processing.   The insula and the ACC have significant numbers of connections supporting a role for their mutual role in a variety of brain functions. 

The insula has been long identified as a sensory region for the gut and body.  New anatomical and imaging research has identified significant expanded domains related to the insular cortex including:
  • Interoception (sensing state of gut, heart, pain etc)
  • Body movement
  • Self-recognition
  • Vocalizationand music
  • Emotional awareness
  • Risk, uncertainty and anticipation
  • Visual and auditory awareness of movement
  • Time perception
  • Attention
  • Perceptual decision-making
  • Cognitive control and performance monitoring

Dr. Craig provides a summary of the research supporting the expanded role of the insula in each of  these additional domains.  He notes that the expanding role of the insula is supportive of the James-Lang theory of emotion.  The James-Lang theory of emotion denotes a theory developed independently by William James and Carl Lange in the 19th century.  Their theory states that emotions follow rather than precede the autonomic nervous system changes to environmental stimuli.  So instead of the sequence 1.) see bear, 2.) experience fear, 3.) heart races, the James-Lang theory states the correct sequence is 1.) see bear, 2.) heart races, 3.) experience fear.   The James-Lang theory. 

The evolving research on insular cortex function also supports the somatic marker hypothesis of Antonio Damasio from the University of Iowa.  Damasio proposes that decision making is influenced by somatic/emotional processes that can guide or bias our behaviors.  These somatic/emotional processes are thought to be stored in the ventromedial prefrontal cortex regions.

There are going to be significant discoveries related to a variety of clinical neuroscience disorders that are likely to involve the insular cortex.  There is already evidence of it playing a key role in such diverse disorders as:
  • Autism
  • ADHD
  • Addictions including nicotine dependence
  • Anorexia nervosa
  • Major depression
  • Pain disorders
  • Alzheimer’s disease (in nonfluent primary progressive aphasia)
 I highly recommend both the 10 year anniversary manuscript as well as the 2009 summary of research on the insula.  They are both packed with data and commentary that I found quite revealing and intriquing.

Photo of iPad snap shot of Brain Tutor app with insular cortex in blue courtesy of Yates Photography.

Craig AD (2009). How do you feel--now? The anterior insula and human awareness. Nature reviews. Neuroscience, 10 (1), 59-70 PMID: 19096369

Luo L, Rodriguez E, Jerbi K, Lachaux JP, Martinerie J, Corbetta M, Shulman GL, Piomelli D, Turrigiano GG, Nelson SB, Joƫls M, de Kloet ER, Holsboer F, Amodio DM, Frith CD, Block ML, Zecca L, Hong JS, Dantzer R, Kelley KW, & Bud Craig AD (2010). Ten years of Nature Reviews Neuroscience: insights from the highly cited. Nature reviews. Neuroscience, 11 (10), 718-26 PMID: 20852655

1 comment:

  1. I know this article was a couple of years ago, however I am wondering if any further research has been done in regard to the Insula and the condition known as Selective Sound Sensitivity Syndrome (4S)aka Misophonia? With 4S, the sufferer experiences an extreme fight or flight adrenaline response, akin to disgust, hate and rage. The triggers are from innocent noises such as eating, chewing, swallowing and other mouth sounds that don't bother most people. It's a debilitating disorder that robs sufferers of their social life and it is something of which the sufferer is not in control. Thank you for your consideration and any links or answers you may be able to give me. Sincerely, Anne Berryessa