Friday, February 09, 2007

The Insula is having its ten minutes of fame...

Those interested in how the brain's parts work to put it all together find their focus shifting as recordings and data begin to appear for previously neglected or inaccessible areas. There have been periods of focus, for example, on the hippocampus (learning and memory) and amygdala (fear and other emotions). Now the insula, on the interior of the cortex, is being found central to our feeling experience. (If you enter insula in the search box to the left of this posting you will find it the subject of several previous posts, one here.) Blakeslee draws together an interesting summary in this week's science section of the New York Times.

Here are some clips from that article:

"... the insula “lights up” in brain scans when people crave drugs, feel pain, anticipate pain, empathize with others, listen to jokes, see disgust on someone’s face, are shunned in a social settings, listen to music, decide not to buy an item, see someone cheat and decide to punish them, and determine degrees of preference while eating chocolate. Damage to the insula can lead to apathy, loss of libido and an inability to tell fresh food from rotten."

credit: New York Times

"The insula itself is a sort of receiving zone that reads the physiological state of the entire body and then generates subjective feelings that can bring about actions, like eating, that keep the body in a state of internal balance. Information from the insula is relayed to other brain structures that appear to be involved in decision making, especially the anterior cingulate and prefrontal cortices...The insula was long ignored for two reasons, researchers said. First, because it is folded and tucked deep within the brain, scientists could not probe it with shallow electrodes. It took the invention of brain imaging techniques, such as functional magnetic resonance imaging, or fMRI, to watch it in action."

" ...the insula receives information from receptors in the skin and internal organs. Such receptors are nerve cells that specialize in different senses. Thus there are receptors that detect heat, cold, itch, pain, taste, hunger, thirst, muscle ache, visceral sensations and so-called air hunger, the need to breathe. The sense of touch and the sense of the body’s position in space are routed to different brain regions."

"All mammals have insulas that read their body condition... Information about the status of the body’s tissues and organs is carried from the receptors along distinct spinal pathways, into the brain stem and up to the posterior insula in the higher brain or cortex...Humans, and to a lesser degree the great apes, have evolved two innovations to their insulas that take this system of reading body states to a new level...One involves circuitry, the other a brand new type of brain cell...In humans, information about the body’s state takes a slightly different route inside the brain, picking up even more signals from the gut, the heart, the lungs and other internal organs. Then the human brain takes an extra step, Dr. Craig said. The information on bodily sensations is further routed to the front part of the insula, especially on the right side, which has undergone a huge expansion in humans and apes...The second major modification to the insula is a type of cell found in only humans, great apes, whales and possibly elephants... Humans have by far the greatest number of these cells, which are called VENs, short for Von Economo neurons, named for the scientist who first described them in 1925. VENs are large cigar-shaped cells tapered at each end, and they are found exclusively in the frontal insula and anterior cingulate cortex...Exactly what VENs are doing within this critical circuit is not yet known...but they are in the catbird seat for turning feelings and emotions into actions and intentions."


  1. Anonymous12:04 AM

    So when you refer to ""... the insula “lights up” in brain scans when people crave drugs, feel pain, anticipate pain, empathize with others, listen to jokes, see disgust on someone’s face," are you referring to functional MR imaging used to map cerebral blood flow changes, or effects on glucose metabolism using positron emission tomography? I would guess they're using fMR imaging. It's certainly a much more efficient and reproducable technique, but still quite difficult. There has been a recent surge in production of high-field open standing MRIs, which would allow more complex tasks during the exam, without being confined within a 60 cm diameter tube. Faster scanning techniques and higher field strength magnets definitely provide more accurate assessment. Current clinical applications of brain mapping techniques are primarily for presurgical planning for resection of intracranial tumors, seizure foci, and vascular malformations. There's a nice article in Magnetic Resonance Imaging Clinics of North America, MR Neuroimaging: Current and Newer Techniques, Volume 11, Number 4: Functional MR imaging: paradigms for clinical preoperative mapping, that desribes in detail methods of mapping cognitive, motor and visual functions..

  2. Thanks for your comment. I should have expanded a bit. Yes, it is almost entirely fMRI data. Also some of the information is from people with lesions from strokes. The new MRI machines you mention which give more space to the subject are going to result in an explosion of studies.