Caregivers should be aware that seemingly inappropriate responce from HD patients may be because of an inability to detect disgust. It is not a attitude problem. It is a HD problem. --Jerry 10/18/00
By Nicolle Charbonneau,HealthScout Reporter, 10/17/00

The recoil … the look of distaste … the retching sounds -- to most of us, it's obvious when someone is disgusted. Now, researchers think they've pinpointed the part of your brain that recognizes when someone else is grossed out.

A British study in the November issue of the journal Nature Neuroscience describes a man whose brain injury left him unable to reliably recognize disgust in others. The research, lead by Andrew Calder at the Brain & Cognitive Sciences Unit in Cambridge, may help explain why patients with Huntington's disease develop this problem -- that neurodegenerative disorder damages the same regions of the brain.

Previous brain scan studies by researchers in London had suggested these areas are involved in recognizing facial expressions of disgust. But Calder's study is the first to look at whether these regions are also involved in recognizing other cues, such as verbal tone or non-verbal sounds.

The patient in the study was a 20-something man who had suffered a stroke, causing brain damage to the insula and putamen regions of his brain.

He could recognize anger, happiness, fear, surprise or grief -- both from images of people's faces or from vocal cues such as crying or laughter.

He could understand the concept of disgust, and responded appropriately to disgust-provoking scenarios, such as an image of a filthy toilet.

But when confronted by images or vocal cues or disgust, he was flummoxed. "The results showed that facial expressions of disgust were indeed impaired in this patient, but on top of that, he also had difficulty recognizing disgust … from vocal expressions."

Calder says the patient took far longer to process the images or vocal cues of disgust, and was far more likely to misidentify the emotion. "The tendency was to miscategorize it as anger," he says.

His previous work has looked at patients with Huntington's disease, which affects roughly 30,000 people in the United States.

"Patients with Huntington's disease are very bad at recognizing facial expressions in general, but showed particular difficulty in recognizing facial expression of disgust," says Calder.

His team is now planning to study how disgust is processed from other sensory inputs, such as taste and smell.

The human emotion of disgust can have a moral dimension, as evidenced by our response to something like child abuse, says Calder.

But a theory developed by Paul Rozin at the University of Pennsylvania suggests disgust has evolved from the gut reaction that protects animals from rotten or poisonous foods.

But Rozin notes this latest article takes the study of disgust to a new level.

"Its major interest is for understanding how the brain organizes emotion," says Rozin, a professor of psychology. "The fact that the brain separately processes recognition of disgust as opposed to other emotions says something about how the whole thing is organized."

Rozin suspects that the ability to recognize disgust may be "hard-wired" into our brains.