The Corpuscle

Patient SM is a 38 year old female suffering from a rare genetic disorder that causes bilateral damage to her amygdala. The most notable symptom of this damage is that SM seems incapable of recognizing fear or terror in other people's faces: She does not exhibit normal fear responses. Her behavior toward others is trusting and friendly where people not suffering from her condition would be wary. SM's other cortical and subcortical structures show no damage. Perception, memory, language, and reasoning abilities (so long as they do not require processing emotional material) are unimpaired. Patient has little or no difficulty recognizing happiness or other emotions, except fear, in the faces of others. Research on SM's condition first began ten years ago.

A few days ago, I wrote in here about the Eyeswhite Project. The essence of that post was that according to a recent study published in Science, the amygdala in a human being will "light up" when its owner sees an abnormal amount of white surrounding the pupils of another person's eyes. That is, there is a more or less automatic fear response triggered in us (or, at least in our amygdalas) when we see someone whose eyes are abnormally wide open.

So what's the deal with Patient SM? Why doesn't she share this normal fear response with her fellow human beings?

Well, it turns out she does. The problem turns out not to be that her amygdala doesn't light up when she sees abnormally wide-eyed fear in others; the problem is that she doesn't look at other people's eyes.

The current issue of Nature (article itself is subscription only) reports recent research on Patient SM, and the simple and straightforward discovery that if she is instructed to look at the eyes of a human face exhibiting that "wide-eyed scared look", she is perfectly capable of accurately reporting that the person looks frightened. Researchers discovered that it wasn't her ability to interpret that look that was lacking; what was lacking was the normal human reaction to check the eyes of others.

Unfortunately, so far at least, she has to be continually told to look. If she isn't, she won't look and so continues to not recognize fear in other people. It's not clear yet, apparently, whether she can eventually be retrained to do it on her own without having to be constantly reminded to do it.

The authors of the article propose this discovery may have implications for research on other "affect disabilities" such as autism. If true, that would be wonderful, but I doubt things are going to be that easy.

If you want to read more about Patient SM but don't have a subscription to Nature, there is a brief "" article here, or you can find a number of articles by using Google News to search on "amygdala".