- Researchers intertwined the identify of food and the pleasure you feel when eating it.
- So far, they’ve performed the experiment on mice.
- They’ve done this by manipulating neurons in the amygdala (a brain region).
- The study provides new techniques to understand and treat eating disorder.
Our tongue has multiple taste receptors and each one of them perceives 5 basic tastes – sweet, salty, bitter, soul and umami – but it is the brain that assigns meaning to these chemicals.
Recently, researchers at the Columbia University showed that the mice brain’s underlying desire for sweet or dislike for bitter could be eliminated by altering neurons in the specific portion of the brain.
That specific portion is called Amygdala, which is responsible for the response and memory of emotions. This subcortical brain structure (in human and other animals) is connected to both fear responses and pleasure. It also produces an array of memories, thoughts, and emotions when tasting food.
How Did They Do It?
The brain does a lot of work when you taste something; it detects the quality of the food and forms unique neuronal signals linking the taste-experience to its memories and emotions, to create a coherent response.
Taste Receptors
Researchers discovered that the complex taste system in the brain are actually multiple units, which could be separately manipulated or deleted. Their aim was to find all these units that assign meaning and context to taste.
One of the early researchers of the author (Dr. Charles S. Zuker) and his team showed that the tongue receptors send signals to specific parts of the brain, where they identify the taste of the food and trigger suitable actions and behaviors.
To understand things better, the team concentrated on amygdala and two basic tastes: bitter and sweet. They successfully demonstrated that the amygdala is directly linked with taste cortex. There is a clear division between bitter and sweet portions of the taste cortex.
In the latest research, they discovered that this division goes all the way into the amygdala. This makes it possible to independently alter these portions of the brain and monitor behavioral changes (if any).
Neural projection from bitter (red) and sweet (green) in the amygdala of mice | Credit: Li Want/Columbia University
Researchers carried out numerous experiments in which they artificially switched off/on the bitter or sweet links to the amygdala. The mice treated tasteless water as if it was sugar, when the sweet links were turned on.
Reference: Nature | doi:10.1038/s41586-018-0165-4 | Columbia Zuckerman Institute
Also, they tweak the same kind of links to alter the perceived taste-quality. This turned bitter into a delightful taste, and sweet into an unpleasant taste.
On the other hand, when links to amygdala were turned off without changing taste cortex, the mice were still able to recognize and differentiate between bitter and sweet. However, they lacked some basic reactions, such as distaste for bitter and preference for sugar.
What they’ve actually done is they’ve intertwined the food’s identity and the pleasure you feel when eating it. All these outcomes give an anatomical substrate to impose hedonic value to bitter and sweet, and the fundamental logic for the formation of hardwired, delightful and unpleasant taste responses.
How This Research Could Be Helpful?
The study provides new methodologies to understand and treat eating disorders like anorexia nervosa and obesity.
Researchers plan to investigate other portions of the brain that play an important role in providing meaning and context to taste. For instance, taste cortex is also directly connected to portions involved in memory, learning, motor actions and multisensory integration.
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Also, the authors believe that the research will help us better understand how our brain handles and processes sensory data and how it adds richness to sensory experiences.
