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Wednesday, 3 June, 1998, 07:25 GMT 08:25 UK
Brain links taste and disgust
Taste and the emotional feeling of disgust are governed by the same areas of the brain, researchers have learned.

The discovery has important implications for the treatment of people with the psychiatric illness Obsessive Compulsive Disorder (OCD), many of whom have an exaggerated preoccupation with cleanliness.

Tests on volunteers asked to look at pictures of faces with different expressions also showed for the first time that fear and disgust are completely separate emotions.

It has long been known that the right side of the brain is the seat of negative emotions, particularly sadness and fear.

The source of fear, thought to be a primitive emotion, has been identified as a lowly part of the brain called the amygdala, an area humans share with many other animals.

But the new study surprised scientists by revealing disgust originates in a different area, the anterior insular cortex, part of the brain's outer layer, known as "grey matter", which deals with higher functions.

Facial expressions are thought to have developed to communicate emotional feelings, an important ability for social animals like humans.

Thus, a look of fear warns others to be on guard for something dangerous, and a look of disgust is a warning to be careful of something "disgusting", such as decaying food.

Avoid contamination

Disgust appears to be a higher brain function which, linked with facial expressions, helps the individual avoid sources of harmful contamination.

The research, led by Dr Mary Phillips, was carried out at the recently merged King's School of Medicine and Dentistry and the Institute of Psychiatry in London.

Brain responses of volunteers shown photos of faces with fearful, disgusted and neutral expressions were measured using a sophisticated scanning technique.

A report on the results in a King's College research review said: "The most striking finding was the activation of the right insula for disgust while there was no activation of the amygdala.

"The anterior insula has been identified in primates as the area responding to both pleasant and unpleasant taste. Activation of the anterior insula while looking at facial expressions of disgust suggests application of visual stimuli depicting others' disgust is closely linked to the perception of unpleasant tastes and smells."

Great clinical significance

The report said the work would have "great clinical significance" in the field of OCD, a condition in which sufferers perform bizarre rituals such as constant handwashing or checking of light switches in order to ward off the negative thoughts with which they are plagued .

Disgust - the word comes from the Latin for bad taste - was the overriding emotion associated with this disorder. Previous studies had shown that disgust underlay obsessional thoughts with washing and cleanliness.

Further studies involving showing more specific images to OCD patients are planned.

See also:

13 Oct 99 | Medical notes
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