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DIGITAL PEOPLE

computer cursor.The brain-wave method requires no brain surgery; however, it receives information from many neurons, a mixture that is difficult to interpret and put to optimum use.The pure signal from a single neuron is easier to analyze. For this reason, many BMI research- ers want to implant electrodes in the brain to obtain well-defined signals from individual neurons. Several of these efforts are distinctly cyborglike, using a living brain to control an external device.

A case reported in 2000 might be the closest we have yet come to a natural brain devoted to an artificial body, like the dancing cyborg Deirdre in C.L. Moores story No Woman Born”—except that this real-life cyborg did not use a human brain. Sandro Mussa-Ivaldi and his team at Northwestern University Medical School wanted to learn about connections between sensory information and motor responses in organic brains, so they created an animal cyborg. Its brain came from a sea lamprey, a predatory eel-like fish, chosen because its neu- rons are large and easy to manipulate.The portion used for the cyborg was the brainstem, which deals with vision and balance and ordinarily issues motor commands to control the animals swimming move- mentsbut in the experiment, the fishs body was replaced by a small two-wheeled mobile robot equipped with a set of light sensors.The brain, kept alive in a nutrient solution for experiments that ran as long as 8 hours, was connected to the light detectors and to the motors controlling the wheels by means of implanted electrodes.

To test the contrivances brainbody interaction, it was placed in a small arena ringed by light sources.As the lights were switched on, the brain received signals from its light sensors and responded by sending signals to the wheel motors, causing the robot to move. Not every installation of electrodes was successful,but when an installation worked well, the device moved consistently either toward or away from the lights, depending on how the electrodes were placed. In short, the artificial body was under the control of an organic brain that produced meaningful motor responses to sensory information, acting in a limited but truly cyborgian way.

Remarkably, cyborglike activity has also been achieved with the more powerful brains of monkeys and humans. In 2000, a group led

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