How Rats Feel: A Whisker's Tale

Science Friday video: Watch rats whisk.

Rats don't have sharp vision, so they rely on whiskers to help them navigate. Reporting in PLoS Computational Biology, engineer Mitra Hartmann, of Northwestern University, and colleagues imaged 354 rat whiskers to create a 3-D model of a rat face to better understand how rats turn the bend of their whiskers into a perception.

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IRA FLATOW, host:

Flora Lichtman has joined us, as always.

FLORA LICHTMAN: Hi, Ira.

FLATOW: You got our video pick this week, Flora?

LICHTMAN: Yes. Yes, we do. This week, we're investigating the whisker.

(Soundbite of laughter)

LICHTMAN: Really, that's really what it's about.

FLATOW: I'm trying to think of a pun. I can't come up with one...

LICHTMAN: I was thinking about that all morning. I don't have...

FLATOW: That's scratchy. That's something that tickles - a ticklish subject.

LICHTMAN: The tale of...

FLATOW: The tale of...

LICHTMAN: It's close - no, I don't have anything good. No, I don't have any good puns. But...

FLATOW: Okay. Okay.

LICHTMAN: Mitra Hartmann, who's the engineer at Northwestern who published this study about whiskers this week, takes this pretty seriously. Anyway, she's really fascinated by whiskers. And when I first talked to her, I was like, you know, what's the interesting thing here? And she summed it up pretty well. She describes it as a rat's sense of touch.

FLATOW: Ooh.

LICHTMAN: So it's really - whisking, which is a verb - is really important for some mammals, like rats and mice. They actually take their whiskers - which they have fine motor control over. They have these muscles that control each whisker.

FLATOW: No kidding.

LICHTMAN: Yeah. It's pretty amazing already.

FLATOW: Wow.

LICHTMAN: And they go to objects and brush them against objects. And from that, they can learn about the shape and even the texture of what that object is.

FLATOW: And your cat, can your cat do the same thing?

LICHTMAN: No, not all animals can whisk. Not all animals with whiskers can whisk, it turns out. So cats, for example, cannot whisk.

FLATOW: Cat lovers are going to be very, very upset that a rat can do something their cat can't do.

LICHTMAN: That's right. But, you know, this is another interesting thing. So we talk about humans having whiskers, but they're not real whiskers.

FLATOW: Oh, you mean like our beards are. We...

LICHTMAN: Yes. Those are not...

FLATOW: Those are not real whiskers.

LICHTMAN: If you don't use them for sensing, it's not a whisker. So cats seem to use whiskers to see if they can squeeze through a hole or something...

FLATOW: Right.

LICHTMAN: ...but rats really go up and use the whiskers like we would touch. And what Hartmann and her colleagues were interested in figuring out was how you translate the push and pull - or the pull - or the push on these little bristles, the bend of these bristles into a perception of the world. So when you think about it, it's just mechanical movement.

FLATOW: Yeah. Wow. And that's our Video Pick of the Week. You have a video of watching how that research is done.

LICHTMAN: You can see some whisking going on. If you're curious what a whisk is, you...

FLATOW: It's not something you make eggs with.

LICHTMAN: It's also something...

FLATOW: All right.

LICHTMAN: ...that rats do. So that's worth a look, for sure.

FLATOW: Mm-hmm. And it's interesting how they show how they geometrically mapped out in three dimensions...

LICHTMAN: Yeah.

FLATOW: ...the computer simulation of what's going on in the whiskers.

LICHTMAN: Right. That's the main - that was sort of the main finding, is scanning these rat heads and coming up with a whisker array. And the other thing is that Mitra Hartmann is interested in sort of making robotic whiskers that you could send into water mains, for example, to whisk out where the cracks are. so there's some irony here because it's a, you know, robo rat whiskers.

But the interesting thing is, you know, I was just asking her about this and she sort of talked about it, but it's really not what gets her up in the morning.

Professor MITRA HARTMANN (Engineer, Northwestern University): No. What gets me out of bed in the morning is the idea that we're gradually being able to understand more about how humans and animals perceive the world.

LICHTMAN: She really convinced me that this is pretty neat research, turning these vibrations, these bends...

FLATOW: Right.

LICHTMAN: ...into perceptions.

FLATOW: Certainly, if you can make little robots that can do this and get into places, maybe find people in rubble, in buildings and things like that by just feeling around, it certainly sounds like it's got really practical...

LICHTMAN: Yeah.

FLATOW: ...practical - and you can go to our website at sciencefriday.com. It's our Video Pick of the Week up there in the left side. And you can watch this terrific computer animation and actually, watch the movement of the muscles individually.

LICHTMAN: You can watch those - each individual whisker and where it is in space and time - something you never knew you wanted to know.

(Soundbite of laughter)

FLATOW: That's right, until you see it.

LICHTMAN: Until you see it.

(Soundbite of laughter)

FLATOW: That's right. I didn't know I - it would be interested. Thank you, Flora.

LICHTMAN: Thanks, Ira.

FLATOW: We'll see you next week.

Our Video Pick of the Week of what's those - whiskers whisk up there on the website at sciencefriday.com. And you can also download it, if you like, as a podcast. You can go to our website, and then you can go to iTunes and download our podcast and also our Video Picks of the Week. Take them along with you in our iPhone and iPad and Android apps. And also, you can catch up on the latest of what's going on in the world of science.

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