Brain-tinkering study leaves bad taste for sugar lovers

PARIS — Have you ever been on a diet and wished that spinach excited your taste buds? Or that chocolate left you cold?

Neuroscientists said on Wednesday they have discovered how to manipulate the brain to make sweet things offputting, and bitter ones nice. But only in mice, for now. Mooting promise for an obesity treatment, researchers in the United States said they have learnt to “switch” parts of the brain’s amygdala on and off, turning sweetness into an aversive taste for lab mice, and bitterness into a desirable one.

“The research points to new strategies for understanding and treating eating disorders including obesity and anorexia nervosa,” said a statement from the Columbia University’s Zuckerman Institute, whose researchers took part in the study.

The method has yet to be tested in humans, however.

In the study, published in the scientific journal Nature, the researchers focused on the amygdalae.

In humans, these are a pair of almond-sized organs in the temporal lobe known to play a role in emotions like fear and pleasure, as well as motivation, survival instinct and stress processing.

The team used laser light stimulation to artificially “switch on” neuron connections to sweet or bitter regions of the amygdala.

When sweet connections were turned on, the lab mice responded to ordinary water as if it were sugar.

In another experiment, the researchers turned the amygdala connections “off ”, but left the taste cortex untouched.

The mice ate, but without showing a preference for sugar, or aversion to bitterness.

“It would be like taking a bite of your favorite chocolate cake but not deriving any enjoyment from doing so,” said study co-author Li Wang.

“And after a few bites, you may stop eating, whereas otherwise you would have scarfed it down.”