A new study has found that the desire for sweet foods, and an aversion to bitter tastes, can be erased by changing neurons in the brain, according to Science Daily. The research suggests that the way the brain tastes food relies on separate systems that can be isolated and altered individually, and could have profound implications for the treatment and understanding of eating disorders like obesity and anorexia.
The study was published Wednesday in the journal Nature. According to Charles Zuker of Columbia University’s Zuckerman Institute, the study’s lead author:
“The very concept of sweet, the very word sweet, implies this goodness, this reward, this craving that we link to it, and similarly bitter on the other side has an immediate meaning to it. So we wanted to know, how does the brain encode meaning on sensory experience?”
The research picks up a thread from Zuker’s earlier work in mapping out the way the brain tastes foods. That work established that when each of the five tastes, such as bitter, salty, or umami, reaches the tongue, specialized cells signal specialized parts of the brain to identify the taste and cause the right type of behavior in response.
For this study, they focused on responses to sweetness and bitterness in the amygdala. This part of the brain is central to the ability to make value judgements of sensory inputs. Zuker’s prior research had shown the amygdala is connected directly to the taste cortex.
The paper’s first author, postdoctoral research scientist Li Wang, PhD, noted:
“Our earlier work revealed a clear divide between the sweet and bitter regions of the taste cortex. 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 study artificially stimulated the sweet and bitter connections to the amygdala. When the sweet connections were activated, mice reacted to water the way they would react to sugar. When they manipulated those connections, they were able to alter the way a certain taste was perceived by the brain, with sweet tastes becoming less desirable, and bitter ones becoming pleasurable.
Turning off the connections to the amygdala but not manipulating the taste cortex left the mice able to differentiate sweet and bitter, but without the emotional preference for sweet tastes.
The research shows that the ability to identify a food can be isolated from the brain’s pleasurable response to it. Altering the function of these parts separately could present a possible approach to treating certain eating disorders in the future.