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What can nature's ugliest rodent teach us about the human brain?
The queen mole-rat peeks
from a tube
For Christopher Comer, it’s a good day when he can walk into his lab, loosen his tie and devote three solid hours to tickling naked mole-rats.
He’s got his own collection of them — 35 rats in four colonies — which a colleague gathered in East Africa and Comer brought with him from his most recent professorship in Chicago. They’re now burrowing, mating and carrying out their daily lives in their new laboratory home underneath UM.
At first glance, it appears evolution has not been tremendously kind to naked mole-rats. They are blind, bald and buck-toothed. They spend their entire lives underground. Farmers in their native East Africa revile them as pests. Perhaps the only animals appreciative of their existence are the snakes and birds that enjoy the wrinkled rats as snacks.
Comer, the new dean of UM’s College of Arts and Sciences, has a poster in his office advertising an exhibit at Chicago’s Brookfield Zoo that just about sums up the critters. “As if being a rat and a mole weren’t bad enough,” the poster reads, above a cartoon of a naked mole-rat looking particularly exposed
“They’re one of those creatures that people have strong reactions to,” Comer admits. “Some people think they’re ungodly ugly, and some people think they’re really cute and fascinating and get really taken with them.”
Researchers Yoshi Baba and Christopher
Comer with part of UM’s new mole-rat colony.
Comer makes no mystery of the group to which he belongs. After researching mole-rats for seven years, it’s clear he’s fond of his rodents. There’s nothing but affection in his voice when he speaks of them.
“These guys are really unusual. They’re eusocial, which is to say they have a social organization that’s like some insects,” Comer says. Every mole-rat colony has one queen, who is larger than the others and responsible for all reproduction. The other rats are divided into a caste system of workers, soldiers and nurses. Their carefully planned tunnel systems can be 2 miles long, housing colonies of up to 200 rats.
“I think it’s a rare biologist who isn’t a bit fascinated by the creatures they work on,” he says. “It’d be hard to put in the time and the effort if you weren’t.”
Hence all the hours Comer devotes to studying his rats, in collaboration with Yoshi Baba, a research assistant professor in the Division of Biological Sciences who came from Chicago to UM with Comer. Both men know that mole-rats, like all mammals worth their mammary glands, reveal a lot about their true nature when tickled.
It’s important to note that “naked mole-rats” is somewhat of a misnomer. While naked mole-rats lack fur, each has about 40 hairs, or vibrissae, on its body. Comer and his students have found that if a tiny filament of metal is attached to a particular vibrissa on the left side of a mole-rat’s body and then vibrated (or tickled) in a magnetic field, they can predict how many degrees the rat will turn to the left. The farther back the hair is on the body, the farther the rat will turn. Tickle a hair on the right side and the animal will turn to the right.
Comer’s research is part of a field called sensorimotor integration, which studies how sensory information in the brain is transmitted to the body as a message that determines a behavioral response.
A worker mole-rat races down a tube connecting the chambers of its UM home.
Monkeys and humans exhibit sensorimotor integration when a light is flashed in their peripheral vision. Even if the light appears only for a few milliseconds, the subject’s brain registers its location and directs the head to swivel until the eyes are aligned with it.
“The brain acquired the information of exactly where it was and sent a set of instructions to the neck muscles to move the head to exactly that target and stop there,” Comer says. “It’s something that seems trivial, but it’s actually not, because it’s a pre-programmed movement.” Often, it happens so fast we don’t even know we’re doing it.
For any sensory stimulus an animal receives, thousands of cells fire off an electrical message on the input side of the brain. Then a translation circuit must rapidly process and decode the signals and send instructions to the muscles of the body to respond.
If this sounds a lot like the Six Million-Dollar Man, don’t worry; a growing number of bioengineers think so, too. Comer says his field of research is attracting engineers eager to harness the power of biological circuits performing sophisticated tasks in order to design brain-operated prosthetic devices and biologically based robots. To do so, they need the help of Comer and other researchers to explain just how the circuitry works.
Scientists have already wired a monkey’s brain waves and used them to move a robotic arm. When the monkey raised its limb, the robot followed suit. “That has obvious applications for what you might call ‘intelligent prosthetic devices,’” Comer says. As a teaching model in his classroom, Comer and a colleague once connected the brain of a cockroach to a microchip in a robot. The robot moved to the left and right according to which of the insect’s antennae was tickled.
When engineers perfect a way to digitize the detailed instructions the brain sends the body, they could, in theory, construct an artificial limb or wheelchair that would move as if it were an extension of the human form.
As profound as the applications of his findings may be, Comer doesn’t focus his research entirely on the practical windfalls of understanding a mole-rat’s brain. He also studies the rodents for their sake alone.
“Curiosity-driven experiments are good for us. I believe that passionately,” he says. “Penicillin wasn’t discovered because a task force said, ‘Let’s develop penicillin.’ Somebody was doing a basic experiment on microbes and noticed something interesting.”
Comer says this curiosity is a hallmark of American science in general and the National Science Foundation
in particular. He directed the Behavioral Neuroscience Program at the foundation from 1993 to 1995 and has received a variety of NSF grants for his research projects.
“When you take bright people, put them in a laboratory and let them figure out how nature works, good things come from that,” he says.
That’s why Comer tries to make it to the lab every Wednesday morning, despite the other obligations inherent in overseeing the 23 departments and programs, 380 faculty, 60 staff and 7,000 students that make up the University’s College of Arts and Sciences.
With a desk piled high in paperwork and every hour of his weekly planner filled with the duties of a dean, it’s a relief for Comer when he can devote time to his rats, even if it means working into the night or on weekends.
“The nice thing about research is that you can say, ‘For the next three hours, I’m going to focus on this one issue,’” he says.
For now, that issue is tickling naked mole-rats. And Comer’s as happy as can be.
— By Jacob Baynham
|(Above) Red light district: Naked mole-rats spend their entire lives underground, so UM researchers study them beneath red darkroom light. These pictures show the colony’s queen being gently handled.