Waltham, MAAs anyone suffering through a head cold knows, food tastes wrong when the nose is clogged, an experience that leads many to conclude that the sense of taste operates normally only when the olfactory system is also in good working order. Evidence that the taste system influences olfactory perception, however, has been vanishingly rareuntil now. In a novel study this week in Nature Neuroscience, Brandeis researchers report just such an influence.
Neuroscientist Don Katz and colleagues discovered that if the taste cortex in rats is inactivated when a rat first smells an odor, at least a food odor, then the rat subsequently will only recognize the food associated with that odor if the taste cortex is again inactivated.
"We discovered that rats use their taste system to smell with, so when you knock out the taste cortex, even for an hour, as we did, you alter their sense of smell," explained Katz. The researchers wrote that "this is the only example of state dependency in neural circuit function of which we are aware."
Katz and his colleagues used a multi-step training process to test the interdependence of the taste and olfactory systems. In the first step, a demonstrator rat that had just eaten chow flavored with one of four spices was introduced to a subject rat, which then smelled the demonstrator rat's breath.
In the second step, the subject rat was offered two choices of chow: one dish with the same flavor previously consumed by the demonstrator rat and another with a different flavor. The subject rat reliably preferred the food that it had previously smelled on the demonstrator rat's breath the day before. The researchers concluded that the social "smell test" of rat's breath is a good enough cue for rats to prefer one food over another.
At the outset they predicted that the rat's sense of smell would not be affected by changes in its taste system. "But we were wrong," said Katz. "Most surpris
|Contact: Laura Gardner|