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Evaluating The Taste Of Food, Drink

Published: February 20, 2017

Yada Treesukosol
PHOTO BY SEAN DUFRENE
Yada Treesukosol

Department of Psychology’s Yada Treesukosol knows all foods and fluids that enter our mouths are evaluated by our sense of taste.

The Australia-born Treesukosol will use that fact in her fourth-floor lab of the psychology building to study how taste, smell and texture control eating and drinking. By mixing pharmacology, electrophysiology and genetic manipulation with meal patterns and detection thresholds, she works to tease apart the relative contributions of oral stimulation and reward-related mechanisms to eating behavior.

Treesukosol, who joined the university in 2016, brings an expertise in psychophysics to her research. Psychophysics is a branch of psychology that describes the relationship between stimuli in the environment and how organisms behave in response to them.

“As a behavioral neuroscientist, this gives me a concrete way to quantify input (e.g. how sweet something is) and output (e.g. how much of the sweet solution the organism will drink),” she said. “Then, once we can quantify this relationship using psychophysics, we can make a physiological manipulation, such as a gene manipulation, giving a drug, damaging a brain area, to see how that relationship changes. We can then make inferences about what the role of that gene/drug/brain area is, in that behavior (e.g. drinking sweet solutions).”

The sense of taste is fundamental to understanding eating disorders and obesity-related complications.

“All foods and fluids that we put in our mouths are evaluated by the taste system,” she said. “Does our sense of taste change thus making individuals more vulnerable to developing eating disorders? Does our sense of taste change thus maintaining some eating disorders? Does an individual who is prone to overeating calorie-rich foods do so because things don’t taste as sweet (so they need to eat sweeter, less healthy foods)? For individuals who lose weight or recover from an eating disorder and then don’t relapse, are they more successful because what used to be tempting or forbidden, not give them the same hedonic value or perhaps taste too sweet?”

Treesukosol is interested in how cues in the environment affect our behavior, noting that first individuals have to understand how they take that in and one way is taste.

“We do it with our tongues, with our guts and with our noses when we smell foods,” she explained. “How do we associate taste with previous learning experiences? How does that big black box in the brain process all that?”

Taste cues are fundamental to treating eating disorders and obesity-related disorders.

“When I ask a mouse if it likes its food, I want to know why the mouse likes it,” she said. “There is plenty of anecdotal evidence from humans that says you eat more as you gain weight. Do we do that because it is so rewarding or because it doesn’t taste as good so I need to eat more to get that satisfaction?”

One tool in her research is a meal-pattern chamber in which rodents live in a box where their food is on a scale. Every time they take the food off the scale, it’s recorded on a computer. Physiological procedures are combined with behavioral measures to analyze detection thresholds. Rodents are given a choice between a lever on the left and a lever on the right. If the stimulus is sweet, the animals learn to respond on the lever on the left. If the stimulus is water, they respond to the lever on the right.

“We decrease the concentration of sweetness and, eventually, the animals will start guessing 50-50,” she said. “This creates a curve of behavior. By comparing curves, I can discover how sensitive the test subject is to sweetness. That is a detection threshold.”

Treesukosol earned her Ph.D. in neuroscience from Florida State University followed by a postdoctoral research fellowship from the Johns Hopkins University School of Medicine.

It is not enough that she knows test animals eat more. As a psychologist, that’s not interesting. She wants to know how they eat more.

“If I give them a high-fat diet and they were hungry before or they had a drug before, they will take more meals,” she said. “Once they start eating, they won’t stop for a long time. In comparison, how many times do we get off the couch to visit the kitchen? If you sit down with a good hamburger, chances are you will keep eating.”

She wants her students to be more aware of the role of taste in their lives, feeling it is important to be aware of these taste cues and the body’s checks and balances.

“There is evidence that suggests tracking your own behavior makes you aware of influences like taste cues,” she said. “We need to understand we are human. Even though we shouldn’t eat cookies, in some situations, we do. We can explain that with science. That way, we begin to understand that proper food management involves lots of decisions every day. How many decisions do you have to make in a single day to eat healthy? Some of those choices will be good and some bad. We need to be OK with that.”