In the Eye of the Beholder
January 24, 2008
Imagine you are at work one morning, sitting at your desk (or wherever you may sit at work), and someone begins walking toward you. You look up and their face is a blur, a completely featureless void that gives you no indication who they might be. You examine their gait, their clothing, and their body shape. This tells you they are a man, but everything else is so nondescript you don’t know if he’s your boss, a visitor, or a co-worker from down the hall. You anxiously look down, hoping the person won’t notice your confusion, as it would seem quite strange since you’ve worked there for years. Only when you hear his voice do you realize he is a friend, simply interested in what you are doing for lunch.
Welcome to the world of a prosopagnosiac. People who suffer from prosopagnosia have an inability to recognize faces. The cause of the disorder, also known as face blindness, is most often some sort of brain damage, such as a tumor or lesion, but there are also congenital cases. A 2006 survey suggested that up to 2% of the population may suffer from prosopagnosia. The severity of the disorder can vary from a subtle blurring of features to the complete inability to recognize faces (even one’s own face) as described in the paragraph above. Prosopagnosiacs often learn to cope with their affliction by focusing on other features of a person that make them recognizable, such as body size, voice, or style of dress. Thus, the account above is slightly dramatized, as an inured prosopagnosiac probably would have been able to recognize a friend based on some of these other qualities before hearing his voice.
Prosopagnosia is a fascinating disorder for many reasons, but perhaps what makes it most amazing to neuroscientists is its specificity. For a long time scientists didn’t know if there were areas of the brain—or individual neurons—so specialized that, when damaged, they could impair only one distinct skill. As prosopagnosia is an example of such a case, it has contributed to our modern understanding of the brain.
Prosopagnosia appears to result from damage to an area in the temporal and occipital lobes called the fusiform gyrus. Neuroimaging studies have identified a specific region of the fusiform gyrus that is activated when a subject views a person’s face. It resultantly came to be named the fusiform face area (FFA). There has been some dispute over whether the FFA is activated only in facial recognition, but its role in seeing faces is well documented. A recent study conducted with prosopagnosiacs demonstrated that the FFA is also used when recognizing beauty in a face. While the brain is amazing for its complex interactions between its various parts, it is also interesting (and sometimes frightening) to realize just how functionally specific some of those parts are.