Number 236 (Story #1), August 7, 1995 by Phillip F. Schewe and Ben Stein
A SILICON DEVICE FOR TRIGGERING ELECTRICAL ACTIVITY IN A NERVE CELL has been constructed, opening possibilities for two-way, non-toxic communication between computer chips and nerve cells. Previous devices for stimulating nerve cells were metallic devices generating ordinary electric currents. Not only do such devices have corrosion-prone electrodes, but their currents create electrochemical byproducts and heat that could damage the nerve cells and themselves. The silicon device, constructed by researchers at the Max Planck Institute for Biochemistry in Germany, contains a "stimulation spot" that triggers neural activity simply through the rearrangement of electric charge. Insulated by silicon oxide, the stimulation spot has a size (between 10 and 50 microns) matched to that of a leech nerve cell to which it is connected. A voltage pulse applied to the spot rearranges electric charge on the silicon oxide film and the insulating membrane of the nerve cell, creating a buildup of positive charge in the nerve cell which causes it to fire above a certain threshold. The silicon device is capable of triggering a single nerve cell without affecting other nearby neurons. The device complements the previously designed "neuron transistor," which receives ionic signals from nerve cells and transcribes them to electronic signals in silicon. "These two devices join the two worlds of information processing, the silicon world of the computer and the water-world of the brain," says the Max Planck Institute's Peter Fromherz (fromherz@vms.biochem.mpg.de). Developing this device for biomedical applications, such as computer-controlled artificial limbs, is not envisioned at the present moment, as researchers will first need to build and understand devices that interact with connective tissue and other non-neuronal cells in the body. (Peter Fromherz and Alfred Stett, 21 Aug., Physical Review Letters; text and figures are available from AIP Public Information, 301- 209-3091, physnews@aip.org.)
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