roviding a biological twist to robotics, scientists have fitted live rats with remote controls to guide them through mazes, past obstacles and even up trees by typing commands on a laptop computer up to half a mile away.
The approach, which takes advantage of an animal's innate ability to do things like climb over rocks, could ultimately be applied to inspecting a disaster area, said the scientists, who report their findings in today's issue of the journal Nature.
"An animal, especially a rat, has much greater facility for getting around in difficult terrain" than would a robot engineered from scratch, said the senior author of the paper, Dr. John K. Chapin, a professor at the State University of New York's Downstate Medical Center in Brooklyn.
The researchers do not commandeer the rats' brains and directly command the animals, zombie-like, where to go. Rather, they take advantage of well-worn techniques of training animals by providing rewards.
The difference is that in the rats, both the stimuli and the reward are piped directly into the brain, and both can be sent by radio signals from some distance away.
Three wires were implanted into the brain of each rat. A pulse of current along one wire stimulated a region of the brain that made the rat feel as if its left whiskers had been touched.
A second wire led to the sensing region of the right whiskers. The third was connected to the part of the brain's pleasure center, the medial forebrain bundle.
The researchers trained the rats to turn left or right when they felt a stimulus in the corresponding whiskers, rewarding them with a pulse of euphoria in the pleasure center.
Strapped on the rat is a tiny backpack containing the antenna for receiving radio signals and a small microprocessor that dispensed the electrical pulses to the rat's brain. The researchers also attached tiny video cameras to get a rat's eye view.
Pressing the keys on the researchers' laptop computer sent the radio commands to the rat: the J key to steer the rat left, L to turn it to the right and K to provide the reward.
The researchers also used a joystick like that used in video games to guide the rats up ladders, down stairs and across narrow ledges.
Unlike robots, animals can quickly adapt to a new terrain. The researchers were able to take the rats, which had never been outdoors, and make them climb trees, scurry along branches, turn around and come back down.
"Our robot friend was astounded," Dr. Chapin said. "He knew what it would take to have a machine climb a tree having never seen a tree, having never come close to solving that physical problem."
That versatility could find use in search-and-rescue operations, Dr. Chapin said.
While robots can survive high temperatures, toxic chemicals and even tumbles of several stories in height, remote-controlled animals might be able to penetrate through tiny spaces that robots cannot.
Dr. Robin R. Murphy, director of the Center for Robot-Assisted Search and Rescue who helped coordinate the use of robots at the World Trade Center wreckage described the research as "very interesting," but added, "I don't think it's appropriate for search and rescue."
The rats would be easily distracted by blood or remains, Dr. Murphy said, adding, "Unfortunately, a lot of this is what rats usually treat as food." Human rescuers and victims would be disconcerted by the sight of rats scurrying around.
"The rats could scare weakened victims to death," Dr. Murphy said.
But she added that remote-controlled animals might be of use in less chaotic environments, like searches for land mines.
Dr. Chapin said he thought many of the problems could be solved.
A wireless computer network could ferry data between a pack of rats so that if one rat were out of direct radio contact with the operator, its signal could still be transmitted through the network, Dr. Chapin said.
And over time, perhaps people could learn to like rats.
"Maybe if it becomes widely known there are these rescue rats," Dr. Chapin said, "people wouldn't be scared."
