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King Wai Yau
You've investigated vision for 30 years, but olfaction only half that time, right?
YAU: Yes. My focus is on the front end—sensory transduction—where sensory stimuli get received and translated into brain signals. Hopkins is the best place in the country for that! Jeremy Nathans works on vision, Randy Reed on olfaction, Craig Montell on vision and chemical senses; Michael Caterina and Xian-Zhong Dong on pain and hot and cold, Paul Fuchs on hearing. Even when there's nothing specific going on, having scientists of that caliber around to bounce ideas off of is fantastic. My olfaction work began about 15 years ago, in collaboration with Randy Reed.
What made you pick it up?
YAU: Randy had cloned what he thought was an ion channel protein for olfaction. Because our lab does electrophysiology, we helped him check out its function. And it was an ion channel, an important one. But in doing that work, I found the commonality between vision and olfaction had whetted my interest—that and Reed's enthusiasm. In both sight and smell, stimuli cause a change in cyclic nucleotides, which activate an ion channel; then a sensory neuron gets depolarized (olfaction) or hyperpolarized (vision).
Is it unusual to add on major interests?
YAU: Extremely few people who work on sensory neuroscience would focus on more than one sense. It speaks strongly for the collegiality at Hopkins , which promotes free flow of scientific ideas. I doubt I would have done it if I'd not been here. Who knows? With our great young scientists around, perhaps, one day, I shall venture into pain research.
As someone who works on more than one sense, how do you think they compare? Are our senses drastically different?
YAU: Well, the stimulus for each sense is different, but in terms of the signaling mechanisms and the proteins involved, most of our senses are quite similar. Hearing, which picks up mechanical vibrations, is sort of the outlier. One important characteristic of vision is that the photoreceptors, especially our rods, can amplify photon signals substantially; this lets us see fairly well even in the dark. Smell receptors, on the other hand, do not appear to amplify olfactory signals as much; instead, an important amplification step takes place in the brain.
The capabilities of our eyes, like the night vision you mentioned, are quite amazing. Of all the features of vision, which would you say is the most impressive?
YAU: The sharp contrast that our eyes can pick out from a scene is astounding. Another impressive property is the ability of the eyes to adjust their sensitivity to the ambient light. You can be in a regularly lit room or out on a beach on a bright sunny day; in either case, you can pick out details pretty well even though the light entering the eyes in the two situations can differ by tens of thousands of times.
What about the ability to see a full color spectrum?
YAU: To some degree, I consider color vision to be a frill—a very nice frill, but I don’t think it’s the most vital component of sight. To put it another way, what would you rather have: a black-and-white TV that has a great picture, or a color TV that’s blurry?
While our eyes are impressive, you appear to be equally intrigued by lizard eyes, specifically their parietal, or “third” eyes.
YAU: Yes, parietal eyes are spots that some animals have on the top of their heads to help them tell the time of day. Recently, we discovered that the photoreceptors in the lizard’s parietal eye combine two mechanisms to detect light, with one similar to that found in rods and cones and the other more akin to the primitive light sensors found in lower animals like scallops. So we really have a unique system to study the evolution of sight.
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