 SENSATION AND
PERCEPTIONMuch of the research at Monell explores the role the chemical senses play in our sensory world. Although tastes, odors, and chemical irritants are rich sources of stimulation throughout our lives, understanding of these complex systems is still unfolding. Monell’s sensory research program focuses on learning more about how we detect and perceive these stimuli and how those processes impact us across our lifespan. It has long been established that our sense of taste detects four basic sensations – sweet, salty, sour, and bitter. More recently, increasing consensus has developed for the addition of a fifth class of taste sensation: umami. Sometimes described as “savory,” “brothy,” or “meaty,” the sensation of umami is conveyed by several substances, including the amino acid glutamate. Glutamate is found naturally in many foods, including fish, cheese, tomatoes, peas, corn, and human milk, and as monosodium glutamate, is often used to enhance the flavor of food.
No one knows exactly how many compounds can stimulate the olfactory system, but it is clear that the number is very large. A single compound may result in a different sensation for one person than another, and it is not uncommon for an individual to experience distinctly different odor qualities when the same compound is presented at various levels of concentration. Throughout our lives, the olfactory system is sending a nearly constant stream of information to the brain. The brain processes this information and organizes it into a coherent whole. Monell’s scientists investigate olfaction at all levels– from the influence of molecular structure of compounds on their perceived odor to the relationships among odor perception, emotion, and memory.
Tastes, smells
and chemosensory irritants are often perceived as mixtures in food or
beverages. A common example is the burning that is often experienced when
eating spicy foods. In this case, the trigeminal nerve carries sensory
information about chemosensory irritation detected in the mouth and throat,
while other nerves carry information about tastes and odors detected in other
parts of the mouth and the nose. All of these sensations are combined in the
brain to produce what is often mistakenly referred to as the ‘taste’
of a particular food. In fact, the combined sensations make up
‘flavor,’ which includes not only tastes, but also odors along with
chemosensory irritation. Naturally the interaction of taste, smell, and
chemosensory irritation is a topic of considerable research interest at the
Center.
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These
five sensations are the foundation for many of the research projects conducted
at Monell. Scientists at the Center are exploring not only fundamental issues
such as how we detect each of these sensations and how that information is
transmitted to the brain, but also more complex issues such as the genetics of
individual differences in taste perception, taste suppression and enhancement
in mixtures, subcategories of tastes (for example, is there more than one type
of bitter or sweet taste?), and taste localization within the oral
cavity.
Chemosensory irritation is the detection of chemical irritants in
the mouth and nose, or on the skin. This sensory system is anatomically
independent from the senses of taste and smell. The detection of chemosensory
irritation can also serve as a warning sign for a variety of potentially
harmful stimuli. However, sensations of irritation — such as pungency,
warmth, cooling, and tingle — are sometimes considered desirable in
certain foods, beverages, and health-care products. Researchers at the Center
are exploring the factors that influence how individuals perceive and respond
to chemosensory irritants, and how different irritants interact.