Remote-controlled rats could soon be detecting earthquake survivors or leading bomb-disposal
teams to buried land mines.

Signals from a laptop up to 500 metres away make the rats run, climb, jump and even cross brightly lit open spaces, contrary to their instincts. The rodents carry a backpack containing a radio receiver and a power source that transmits the signals into their brains through electrical probes the breadth of a hair.

"They work for pleasure," says Sanjiv Talwar, the bioengineer at the State University of New York who led the research team. One electrode stimulates the rat's medial forebrain bundle, or MFB, the 'feelgood' centre of the mammalian brain. "The rat feels nirvana," Talwar says.

Two more electrodes stimulate the brain region that normally processes signals from the rat's left and right whiskers.

Now the team hopes to work out how to record nerve impulses from a rat's nose when it detects an odour such as TNT or the human body. Then 'ratbots' equipped with satellite positioning tags could be used as smart sensors. The research arm of the US defence department is funding the work.

But the research has as much potential in the emerging field of neuroprosthetics according to learning and memory expert Samuel Deadwyler of Wake Forest University in Winston-Salem, North Carolina. Artificial stimulation of brain regions could bypass damaged nerves that once controlled muscles in paralysed people. "This approach could restore those linkages," says Deadwyler.

Learning for pleasure

Talwar's team train the wired-up rats to turn left or right in a maze according to the artificial whisker stimuli. A jolt to the MFB rewards the rats for correct behaviour. After a week's training the rats turn on cue without reward.

Thereafter frequent pleasure pulses motivate trained rats to navigate through virtually any environment. Extra pulses spur them on to challenges like climbing or jumping.

There is a limit to what the animals can be made to do: instinct tempers their eagerness for reward. For example, even continuous MFB stimulation cannot make a rat jump from a dangerous height.

Manipulating animal's minds, especially for dangerous missions, raises ethical questions. "Debate is certainly needed," admits Talwar. But he points out that the rats live as long as normal, and when not wearing mind-altering backpacks they are just like any other rats. "They're not zombies, they work with their instincts," he says.

In a way, ratbots are an extension of classical behavioural experiments in which animals learn to perform tasks in return for food, say. It's just that the reward for leaning, as far as a ratbot is concerned, comes from within. This virtual learning could make ratbots a new model for studying animal behaviour.