Monday, June 21, 1999 Published at 21:17 GMT 22:17 UK
Mind over matter
Rats moved the robot arm by brain power alone
By BBC News Online Science Editor Dr David Whitehouse
Controlling a robot arm by brain power alone sounds like science fiction, but experiments involving rats' brains have brought it closer to reality.
Dr John Chapin, of the MCP Hahnemann University School of Medicine in Philadelphia, has shown for the first time that brain cell activity can be used to control a robotic device.
The scientists trained rats to obtain water from a robotic arm by pressing a small lever. Each rat had electrodes implanted in its brain to record the activity of certain cells.
As the rats performed this task, the scientists analysed the patterns of activity in the regions of the brain that control movement.
They identified specific brain cell activity associated with the rat's paw movements.
The researchers had to develop a new mathematical method to analyse the signals from the brain cells.
Think and move
The next step was to connect the robot arm directly to the rat's brain. The brain now controlled the robot arm directly through the electrodes and the computer.
The rats appeared to have little difficulty in controlling the robot arm. Initially, they continued to press the lever, even though this was no longer necessary to cause the robot arm movements.
But eventually many rats learned that they could obtain water through brain activity alone and stopped pressing the lever.
This is not the first time that brain activity has been used to drive a machine, but it does represent a significant advance.
Previous attempts to control artificial limbs have been based on signals recorded from muscles in the stump of an amputated limb, or electrical brain signals detected at the surface of the scalp.
It is a crude technique that cannot be used for patients who have lost control of their muscles because of spinal injury or motor neurone disease.
By using individual brain cells as the control mechanism it should in principle be possible to achieve far more satisfactory and reliable control of an artificial limb.
But major obstacles must be overcome before it the technique can be applied to human patients.
The robot arm used with the rats is a simple device that can only move in one dimension; recording and decoding enough information to control a device in three dimensions would be considerably more difficult.
The research is published in the journal Nature Neuroscience.