AChemS, Day 3: "How does the tongue know what it is tasting and how does the brain know what the tongue knows?"

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By Nicole Garneau, PhD

The questions pertaining to researching flavor, I'm learning, go far beyond taste. Flavor is a combination of taste, smell and texture. Each of the factors then send signals to the brain (at the primary taste cortex)  which allows it to form an internal representation of the physical and chemical features of what is being consumed.
Tonight I watched an exceptional presentation, from both a scientific and entertaining viewpoint. It was an overview of mammalian taste given by this year's IFF (International Flavors and Fragrances Inc.) platform lecturer, Dr. Charles Zuker.

Why exactly did I enjoy this lecture so? Very simple reasons:

1. It was directional and personable. It began wide-reaching, depicting perception of the world through each of the senses: hearing, sight, touch, smell and of course, taste. A bit of Mozart played in the background as the point was made that our senses allow us to capture the surrounding world in our minds, and not necessarily an exact picture, but a representation that allows us to make decisions and proceed. From there the details emerged concerning taste specifically. It was personable because the presenter was engaging- it felt conversational, even though I was one in a crowd of 500.

2. The story included the forest, not just the trees.  I can tell you that when my life revolved around my lab bench, it was so easy to converse only with those that spoke the same language as I- at that time in my life it was the sweet lexicon of viruses. And let me tell you, when your life revolves around one very small portion of the world at large, and you know everything, and I mean everything about that one thing, It is easy to get lost in it. So I truly appreciate it when a scientist is conscious of this trait and makes an effort to present his or her research in a way that addresses the eternal question of significance.So then, why is taste so important? Well, you can't talk about taste without talking about health. And our decisions about how we treat our bodies, including what we eat, has to do with perception- the information the brain gets and what it does with it. Dr. Zuker aptly posed the following question:

"How does the tongue know what it is tasting and how does the brain know what the tongue knows?"

3. It generated a healthy discourse among experts. Science is funny, I mean it, truly funny. It is not a flowery positive world. In science, you can almost never, in the most absolute form, prove anything. What you can do is supply the most convincing evidence to bring forth a story, while simultaneously disproving other stories. This means that scientists are often uncompromising in their criticisms. If you can't poke holes in a theory, then the theory likely will hold up to the high standards of peer-reviewed research. Discourse in this way is good, it keeps scientists honest.

So, that's why I really enjoyed this talk, but not why I was fascinated. My fascination has to do not with the style of the presentation, but the substance.

The answers to the questions Zuker asked above about the tongue and the brain include knowing how the receptors of taste work, knowing how this information gets to the brain and knowing how the brain processes this information. This last part, well, Zuker is doing some really cool work to answer this with mice. What he has found is that its more than just a receptor (like a lock) that binds to a taste molecule (like a key), but it is also the hardwiring of how these receptors activate the taste cells that report to the brain. It turns out that if you take a bitter taste cell and replace the bitter receptors with sweet receptors, you get an extraordinary result: sweet compounds taste bitter!

Why is this? Well, the bitter cells are hardwired to report bitterness to the brain (like sweet cells report only sweet to the brain), so when the cell gets activated by one of its receptor binding a taste molecule (like turning on a light) it reports the light is on, regardless of how the light got turned on.

With that, It's about midnight or so here, so I think it's time for me to turn off a few lights myself.

Signing off,
- Nicole

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