WASHINGTON, May 30 (Xinhua) -- Research in mice has revealed that the brain's desire for sweet and its distaste for bitter can be erased by manipulating neurons in the amygdala, the emotion center of the brain, according to a study published on Wednesday in the journal Nature.
The study showed that removing an animal's capacity to crave or despise a taste had no impact on its ability to identify it, because the brain's taste system that produces an array of thoughts, memories and emotions during eating are discrete units that can be individually isolated and modified.
The findings pointed to new strategies for understanding and treating eating disorders including obesity and anorexia nervosa.
The scientists led by Charles S. Zuker, a principal investigator at Columbia University's Mortimer B. Zuckerman Mind Brain Behavior Institute and the paper's senior author, studied links between sweet and bitter taste and the amygdala.
Amygdala is a brain region known to be important for making value judgments about sensory information and connecting directly to the taste cortex.
"Our earlier work revealed a clear divide between the sweet and bitter regions of the taste cortex," said Wang Li, a postdoctoral research scientist in the Zuker lab and the paper's first author.
"This new study showed that same division continued all the way into the amygdala. This segregation between sweet and bitter regions in both the taste cortex and amygdala meant we could independently manipulate these brain regions and monitor any resulting changes in behavior."
The scientists managed to artificially switch on the sweet or bitter connections to the amygdala and when the sweet connections were turned on, the animals responded to water just as if it were sugar.
By manipulating the same types of connections, the researchers could even change the perceived quality of a taste, turning sweet into an aversive taste, or bitter into an attractive one.
In contrast, when the researchers instead turned off the amygdala connections but left the taste cortex untouched, the mice could still recognize and distinguish sweet from bitter, but now lacked the basic emotional reactions, like preference for sugar or aversion to bitter.
"It would be like taking a bite of your favorite chocolate cake but not deriving any enjoyment from doing so," said Wang. "After a few bites, you may stop eating, whereas otherwise you would have scarfed it down."
The findings suggested that the amygdala could be a promising area of focus when looking for strategies to treat eating disorders.
