Steven St. John, PhD


Research Interests

Most generally, I am interested in the mind-body problem, or how our body (brains) create and experience subjective states (mind).  We can create a machine that detects the presence of sucrose in a solution, but we don't imagine the solution tastes "sweet" to the machine.  We fill our cars up with gasoline when the meter reads Empty, but we don't imagine that the car feels "hungry".

My first research interest was in taste quality coding - understanding the neural representation of such qualitative experiences as sweetness, saltiness, sourness, and bitterness.  These research interests have generlized into the following current specific areas.


Salt Appetite

People and animals deprived of salt experience a "salt appetite" - a specific sodium hunger.  This is probably related to the "Gatorade Effect" - the observation that electrolyte solutions, like Gatorade, taste better when we've been exercising (and thus losing salts).  In rats, sodium deprivation causes rats to show a dramatic change in their eating and drinking behavior - rats will show a strong preference for concentrated sodium solutions that they would reject as distasteful when sodium replete.  My research has attempted to define and understand the perceptual and neural changes that occur during sodium deprivation.


Neural Control Of Licking

In the course of my taste research on rats and especially mice, my colleagues and I discovered dramatic variations in lick rate among strains of mice.  Lick rate is controlled by a specialized neural circuit called a central pattern generator (CPG).  CPGs have long been of interest to neuroscientists who are interested in, for example, recovery from spinal cord injury, because different CPGs underlie such rhythmic behaviors as walking, running, and swimming.  Because licking is very easy to measure and manipulate, and because inbred strains of mice are useful for genetic analysis, our research may permit the identification of the mechanisms and control of CPGs generally.


The Taste Bud As A Specialized Neural Circuit

A taste bud is a collection of several dozen specialized receptor cells that detect important molecules (sucrose, sodium chloride, etc.) and signal their presence in food to the brain.  Recently it has been hypothesized that these cells communicate with one another inside the taste bud.  We are examining this possibility through behavioral testing of rats and mice with components of this intragemmal (within-taste bud) signalling manipulated (either genetically or pharmacologically).


Development Of Eating Habits In School-Aged Children

We recently obtained a grant, in collaboration with Alice Davidson (Rollins College) and Kurt Thaw (Millsaps College) to study environmental influences on the development of eating habits and obesity in elementary and high school aged students.


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Steven St. John
Professor of Psychology

Bush 320
T. 407.691.1153


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Rollins College
Department of Psychology
1000 Holt Ave. - 2760
Winter Park, FL 32789

T. 407.646.2227
F. 407.646.2685
Office: Bush Science Center, third floor

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