Why do we desire sugary snacks over more nutritious choices? While it ultimately relates to how our brains interpret flavor and our expectations concerning the food before us, a recent study from Florida State University indicates that several brain areas are involved in the mechanism more than previously acknowledged.
A group of FSU neuroscientists discovered that the mediodorsal thalamus, an area of the brain not formerly associated with taste, plays a significant part in how we perceive and anticipate flavors. These results provide new understanding into how dietary preferences develop and why they can be challenging to alter.
The research team, headed by Assistant Professor of Biological Science and Neuroscience Roberto Vincis, found that neurons in the mediodorsal thalamus react both to the sensory characteristics of flavor — such as whether an item is sweet or savory — and to signals that indicate what kind of taste is forthcoming. This implies that this brain region is not only involved in experiencing flavor but also in forecasting it.
This study was published in the Journal of Neuroscience.
“Traditionally, the mediodorsal thalamus has been examined in the context of higher-order functions, including reward evaluation, decision-making, and integrating multiple sensory inputs,” said Vincis, who is additionally connected with FSU’s Institute of Molecular Biophysics. “As a result, it wasn’t regarded as a region that would process or represent fundamental taste data, such as discerning what a flavor is or its intensity, particularly without associations to other sensory modalities like olfaction.”
The gustatory pathway initiates when our taste buds perceive a flavor and concludes with that data reaching the gustatory cortex, a brain area located in the cerebral cortex, or the outer layer of the brain. Sensory data, the information collected from sight, hearing, texture, smell, and taste, is amalgamated with one’s behavioral experience or emotional state during consumption. Often, a single experience is sufficient to establish particular eating habits, such as favoring or disliking specific foods, which can have prolonged effects on our nutrition and well-being.
“This study establishes the groundwork for research that forms part of the broader understanding of diagnosing and addressing taste disorders and other elements of human behavior influenced by taste,” noted Katherine Odegaard, a postdoctoral researcher in the Vincis Laboratory and first author of the paper. “Examining the relationship between the gustatory cortex and mediodorsal thalamus enables us to comprehend how taste information is interpreted in the brain more effectively. Although the mediodorsal thalamus wasn’t previously considered part of the ‘classical’ taste pathway, our research revealed that it indeed processes taste information and expectations related to flavor, suggesting that this area plays a more significant role in our eating behaviors than we had realized.”
The team discovered that the mediodorsal thalamus encodes taste information even without the presence of odor, a groundbreaking finding in the fields of chemosensation and ingestive behavior, and that neurons in this area respond distinctly to varying taste concentrations. This suggests that the mediodorsal thalamus can not only differentiate various taste qualities, like sweet versus bitter, but also identify different concentrations in sweet and salty foods — for instance, sweet but not overly sweet or salty but not excessively salty — in a linear manner; as the concentration of salt or sucrose increased, responses from some neurons rose while others diminished.
Researchers also noted that neurons in the mediodorsal thalamus react not only to taste itself but also to non-gustatory sensory signals, like sounds that indicate whether an imminent taste will be enjoyable or unpleasant, implying that this region assists the brain in preparing for what is about to be encountered.
“It was astonishing to observe how various groups of neurons reacted in our study,” Odegaard remarked. “Some neurons responded solely to certain sounds, like how the melody of an ice cream truck might lead us to anticipate something sweet. Conversely, another group of neurons seemed to reflect not just the auditory cue but also the specific taste it foretold — whether it was enjoyable or unpleasant. It could be that these neuronal groups play a more prominent role in steering behavior through anticipated outcomes, which is another reason to pursue further research into the mediodorsal thalamus.”
Additional contributors include FSU alumna and current adjunct instructor at Pensacola State College Cecilia Bouaichi and biomathematics Ph.D. candidate Greg Owanga.
This research received funding from a $1.8 million grant from the National Institute on Deafness and Other Communication Disorders, part of the National Institutes of Health, awarded to Vincis in 2022 to explore how the brain encodes information about food and the impact of this data on an individual’s overall eating habits and food selections.
To learn more about research conducted in the Vincis Laboratory, visit bio.fsu.edu/vincislab. For more information about the Program in Neuroscience, explore neuro.fsu.edu.
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