Nell (not her real name) was shivering, but she did not realize she was cold. Only when a colleague pointed out her goose bumps and blue lips did she think to put on a sweater. Nor does she register feelings such as exhaustion. “Sometimes I don’t realize I’m tired until three in the morning,” she says. “I just don’t get those clues correctly.”

These traits seemed like little more than quirks until September 2010, when the 36-year-old woman took a full battery of psychological tests as she reentered treatment for a relapse of anorexia nervosa, a disorder she had struggled with on and off for more than 20 years. One of the tests included a section measuring a little-known sense called interoception, awareness of the internal state of one’s body. Interoception informs us of emotions, pain, thirst, hunger and body temperature. People vary on how well they receive such cues. As with other individuals who have eating disorders and body image issues, Nell showed profound difficulties with interoception.

6 Comments

1. 1. jputz 07:42 AM 4/15/12

   I read with interest the article. I do question calling interception a sense, at least without describing what the author means by a sense. It is not one modality. Rather, it brings different modalities together (sense of touch, pain and temperature from within the body, visual perceptions, and emotional and mental states such as hunger). It doesn't involve primary sensations the way our real senses (e.g., vision, hearing) do, but rather perceptions. It is really a group of perceptions about our the internal state of our body. So rather than calling interception a sense, I would say that interception refers to a group of perceptions about the internal mental and physical state of our bodies.
   
   I wonder how interoception is different in people who lie on the autistic spectrum. In anorexia, people have trouble perceiving themselves, apparently, in part, how they integrate information about their own bodies. In autism, people have difficulty perceiving or inferring the internal state of others from visual and other clues. Comparing and contorting disorders in interoception and autism would be quite interesting.

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2. 2. r.elizabeth 11:15 PM 4/16/12

   When I read the title I was excited to see what it had to say, and although I think there were some good points, I was ultimately disappointed. I was first alerted by the imaging pictures from the study published by Sachdev et al. (2008). At first glance it looks like anorexic nervosa (AN) patients show no/very little activation within the brain in response to self-images. This doesn't make sense given the lack of occipital activation. Closer inspection of the original article reveals that it represents a contrast between non-self versus self images. This should be made more clear in popular press articles in order to avoid confusion. Furthermore, at one point the original research article goes on to say that there was parahippocampal and fusiform gyrus activation, supporting previous research that AN women perceive distorted images of their own bodies by complex cognitive processing of emotion. If this is the case one would expect amygdala, insula or ACC activation. It then later states that AN patients suppress emotional processing of information. This contradicts other research demonstrating that the "fear network" is recruited when AN patients view self-images (which includes the amygdala and insula). Researchers then conclude that insula dysregulation could be responsible for distorted body images. I argue that it's possible the participants didn't even identify with the "self-images" given that the faces of the stimuli were blotted out and the attentional network did not show significant activation.
   
   My goal here isn't to nit-pick, but I do wish that The Scientific American would look more closely into the research that they publish. Presenting alternate sides to a research argument provides a more holistic and comprehensive review that is much more valuable to the readers.
   
   R

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3. 3. ultimobo 08:21 AM 4/19/12

   interoception, awareness of the internal state of one’s body - reminds me of hunger signals ...
   
   as a skinny guy perhaps growing up with negative associations with food (parents argued at meal times) I tend to not feel hungry and forget to eat, only noticing when I get acid pains burning my stomach. I also feel full early and often stop eating before others eating same-sized meals.
   
   I always remember one restaurant meal with an slightly overweight woman - we both ate the same amount till I felt stuffed and stopped, then watched with a mixture of amazement and horror as my female companion seemed to change into a higher gear and accelerate, eating more and faster, almost the same amount again. So while I noticed the full switch and stopped, I guess she wasn't responding to any such full signal.
   
   Wiring or psychology - I'm not sure ...

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4. 4. DonPaul in reply to jputz 01:23 PM 4/19/12

   For there to be only perceptions (which are presumably contained in the brain proper) of the internal state of a body then there will be NO INTERNAL sensor neurons. This is obviously not the case. We are loaded with all sorts of internal sensors. Proprioception comes to mind. Shoot even the body's temperature sensors are actually sensing the INTERNAL temperature - not the external. Stomachs have many many sensors. This is all much more than perception. The action of ignoring these sensations is very much equivalent to ignoring the sounds around you. It is fundamentally a choice of some sort = An interesting psychology question for sure.

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5. 5. justamom in reply to DonPaul 08:16 AM 5/19/12

   As the parent of an anorexic/bulimic daughter, I've read with interest the comments made by others about this article.
   
   Our personal experiences match up with the points made by the author. Our very intelligent daughter has a high threshold for pain and a lack of coordination. She misreads sensations of hot and cold and hunger and fullness, and she can be unaware of the severity of an illness or injury. She is easily influenced by others even when she is aware of consequences. There is a perception glitch in the brain.
   
   The downward spiral begins when individuals with anorexic tendencies start depriving themselves of nutrition. Several articles have been written about the effect of starvation and poor nutrition on the brain. From what I've read, anemia can be a factor in depression. The perception glitch turns into major distortion. Anxiety is exacerbated by the lack of nutrition, and the embarrassment of having your life get that far out of hand prevents a lot of people from getting treatment.

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6. 6. Ettina in reply to jputz 10:03 AM 6/4/12

   I'm high functioning autistic, and I took the interoception test and scored .53 (below .60 is poor). I've long known that I can't tell when I'm hungry, and I'm very poorly coordinated partly because I have trouble feeling where my limbs are (I also have poor balance and hypermobility, which doesn't help).
   And sometimes, when I look in the mirror, my face looks 'wrong' somehow, like I thought I looked different from how I actually do, or like it's not really me in that mirror. It's not an unpleasant feeling, just really strange.
   I've never been anorexic, mainly because I don't want to be thin. In fact, although I now know that I'm actually normal weight, I used to think I was *too* thin (possibly because both my parents and my brother are fat) and wanted to gain weight, but I never had the self-discipline necessary to control my own diet. So I think I'm not anorexic for two reasons - I don't want to be thin, and I don't have much self-control.
   Oh, and to DonPaul - sensory processing issues aren't a choice. After your physical receptors gather the information, it goes to some non-conscious parts of your brain to get processed. Some stuff gets screened out as irrelevant (eg other people's conversations in a crowded place) and other stuff gets marked as important (eg the sound of your name). Other non-conscious parts of the brain process what the sensation actually is, such as recognizing the object you're seeing. Only after all of that is done do you actually consciously experience the sensation. And if any of that goes wrong, you can have a fundamentally different sensory experience despite having normal sensory receptors. For example, my hearing is probably normal, but I act hard-of-hearing in noisy places because I can't tune out background noise and it's all too much to process.

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