Researchers have a hard time locating the brain areas involved in specific human emotions. But a patient with brain damage has provided scientists in the United Kingdom with a dramatic opportunity to show how particular brain regions are involved in a basic emotion: disgust. The study shows that recognizing disgust in others activates the same brain areas as the feeling itself.
Images of normal brains have shown that disgust activates two particular regions: a part of the cortex called the insula and a subcortical region, the putamen. Now researchers at Cambridge University have probed this phenomenon in a 25-year-old man with stroke damage specifically in the "disgust" areas. Psychologist Andrew Calder and colleagues showed him pictures of people expressing six different emotions. They found that he had no difficulty recognizing happy, fearful, angry, sad, and surprised expressions. But he had problems recognizing disgust. It wasn't just faces; he also didn't recognize retching sounds or numbers recited in a disgusted tone.
What's more, disgusting photos and disgust-provoking ideas--such as friends who change underwear once a week or chocolate in the shape of feces--elicited an "abnormally low" emotional reaction compared with a group of normal controls, the researchers report in the November issue of Nature Neuroscience. However, Calder says the subject understood that others would find these disgusting--he just didn't feel disgusted himself.
Calder speculates that the striking localization for disgust could derive from the fact that it, like fear, is "important for basic survival." An aversive reaction to rotten meat, for example, can be lifesaving. Other major emotions such as anger and sadness are less clear and consistent in their patterns of brain activation, he says.
Research such as Calder's is "opening the way for discovering a level of specificity in brain function that we hadn't realized," says psychologist Paul Rozin of the University of Pennsylvania in Philadelphia. Jaak Panksepp, a psychobiologist at Bowling Green State University in Ohio, says the study confirms a notion that he and others have supported for some time: The ability to interpret someone else's emotional expression involves the same brain areas as the emotion itself.
Andrew Calder's home page