Scientists find the brain switch to 'turn off' the desire for sweets

The manipulation of a group of neurons in the amygdala nullifies the pleasure sensation caused by sweets, which could be very useful to treat eating disorders.

Children will go for sweets. Not so much adolescents and, above all, adults, since the preference for sweet foods usually decreases with age. But, obviously, it does not always happen that way. In fact, it is already known that reward systems in the brain do not work the same in obese people as in 'thin' ones, which could explain why the loss of appetite for sugar-rich foods is not as pronounced in individuals with a high body mass index (BMI) and continue, in time, eating sweets. However, there could be a way to nullify this longing for sugars. And is that researchers at Columbia University in New York (USA) have found the brain switch that triggers the desire for sweets and, at the same time, causes rejection by bitter foods.

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Specifically, the study published in the journal "Nature", shows that the cerebral system of processing flavors, responsible for releasing the memories and emotions that are triggered when a food is savored , is formed by small sets of neurons that can be isolated, modified or eliminated. Thus, and in regard to the desire for sweets - and the rejection of bitter foods -, 'only' would have to manipulate a group of neurons located in the amygdala to end, once and for all, with this longing.

Sweet or bitter?

The authors of the new study have been trying for years to map the brain system responsible for processing flavors. A work that, among other targets, has revealed that when the tongue meets one of the five tastes - sweet, bitter, salty, acid and umami - the specialized cells of the taste buds send signals to different regions of the brain so that identify the flavor and trigger the corresponding responses and behaviors -basically, acceptance or rejection-.

But the authors wanted to go a step further. Specifically, what they wanted was to analyze the responses that sweet and bitter flavors are triggered in the amygdala, that is, the brain region responsible for issuing value judgments - positive or negative - about sensory information. An amygdala, moreover, that is already known to be directly connected to the gustatory cortex - the brain structure responsible for the perception of taste.

The amygdala is a very promising therapeutic target for the treatment of eating disorders, anorexia or obesity.

As Li Wang, co-author of the research, explains,

"our previous work already revealed a clear division between the 'sweet' and 'bitter' regions of the gustatory cortex. And now, our results show that this division also stays in the amygdala. Thus, this segregation between the regions 'sweet' and 'bitter' in both the gustatory cortex and the amygdala allows us to manipulate them independently and detect any possible change in behavior.

The authors conducted a series of experiments in which the 'sweet' and 'bitter' connections of the amygdala were artificially activated. And what they saw is that when they 'lit' the 'sweet' connection, the animals responded to the water as if it were sugar. And what is more important, they observed that by means of these manipulations they could change the perception of the animals about each flavor. For example, they could cause the sweet flavors to be recognized as 'undesirable' and the bitter tastes to be perceived as 'attractive'.

But there is still more. The results also showed that by turning off the connections - or 'switches' - of the amygdala without touching those of the gustatory cortex, the animals, while retaining the ability to recognize and distinguish the sweet and bitter tastes, felt no emotion about them, so they had no preference-or aversion-for any one in particular.

As Li Wang points out,

"It would be like taking a bite out of our favorite chocolate cake but not experiencing any pleasure in doing so. Thus, after several bites, one would stop eating, while otherwise it would not stop until it was finished ".

In short, the study identifies the specific area of ​​the brain, or what would be the same, the brain 'switch', which triggers our sense of pleasure - or aversion - when we eat food. A finding that suggests that the amygdala could be a very promising therapeutic target for the treatment of eating disorders and, therefore, of obesity.

As Charles S. Zuker, director of the research concludes,

"when our brain" feels "a taste it not only identifies its quality, but it orchestrates a wonderful symphony of neural signals that link this experience with its context, hedonic value, memories and emotions, to produce a coherent response ».

Therefore, what would be intended is to press the switch in the amygdala to silence this symphony.

Source: Love for Sweets Located in Brain’s Emotion Center