Send in the rescue rats


RATS equipped with radios that transmit their brainwaves could soon be helping to locate earthquake survivors buried in the wreckage of collapsed buildings. Rats have an exquisitely sensitive sense of smell and can crawl just about anywhere. This combination make them ideal candidates for sniffing out buried survivors. For that the animals need to be taught to home in on people, and they must also signal their position to rescuers on the surface. In a project funded by DARPA, the Pentagon's research arm, Linda and Ray Hermer-Vazquez of the University of Florida in Gainesville have worked out a way to achieve this. First the researchers identified the neural signals rats generate when they have found a scent that they are looking for. "When a dog is sniffing a bomb, he makes a unique movement that the handler recognises," says John Chapin, a neuroscientist at the State University of New York in Brooklyn who is collaborating on the project. "Instead of the rat making a conditioned response, we pick up the response immediately from the brain." Each rat has electrodes implanted in three areas of the brain: the olfactory cortex, where the brain processes odour signals; the motor cortex, where the brain plans its next move; and the reward centre, which when stimulated gives the rat a pleasurable sensation. The electrodes, each consisting of an array of up to 32 stainless steel wires 75 micrometres in diameter, are permanently implanted in the brain and can give accurate signals for up to nine months. The researchers trained the rats to search for human odour by stimulating the reward centre when it found its target smell. Once the rats were trained, they were set to forage for the target smell, while electrodes recorded their neural activity patterns. This allowed researchers to identify the brainwave patterns associated with finding that smell.

They were also able to train the rats to sniff out the explosives TNT and RDX- key after terrorist attacks that may leave buildings harbouring unexploded bombs. "There are two neural events that we believe are hallmarks of the 'aha!' moment for the rat," says Linda Hermer-Vazquez. These are high-frequency activity in one subset of neurons, and decreased activity in two other areas, she says. Signals from the rat's brain will be relayed to a radio transmitter pack strapped to the animal's back, which Chapin is developing. Rescuers will be able to follow the rat's position by tracking these signals. They are also developing software that will recognise the "aha!" moment when the rat has found its target, so rescuers will know where to start digging. The team hope to create a working system within nine months. Other teams looking at ways to seek people trapped under debris have designed wheeled, tracked or even snake-like robots that can slither into wrecked buildings (New Scientist, 10 November 2001, p 22).

But rats have several advantages. "Artificial noses don't work well when there are other smells around," says Christiane Linster, an olfaction expert at Cornell University in New York. "Rats are good at that." Rats are also adept at navigating over unexpected obstacles, and of course they don't need an electricity supply. Rescue teams welcome the idea. "It would be absolutely fantastic," says Julie Ryan of International Rescue Corps in Scotland, which flies rescuers to disaster zones around the world. "A rat could get in voids and spaces we couldn't get to. And a rat would try to get out if it didn't feel safe."

Source: Eurekalert & others

Last reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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