Dave Kewley stands in front of a large laboratory cabinet gingerly cradling a wafer-thin sheet of silicon in the palm of his hand. Etched on the surface of the silicon sheets are tiny silicon probes with electrodes on the tips. Barely perceptible to the naked eye, the probes are shaped like microscopic pitchforks that might be used by Lilliputian farmers in some parallel universe. The tines of each "pitchfork" are 25 microns in diameter, or about one-third the width of a human hair, and in concert, they serve as miniscule microphones that detect the action inside the neuronal cells.

These probes represent a new level of precision. In the past, such probes have resembled miniature beds of nails and, in general, measured activity in one nerve cell at a time. The new generation created by Kewley, with colleagues at Stanford University, is so sensitive it can record signals from groups of neurons in the living brain. After all, say Kewly and Bowers, the only way to decipher the architecture of the brain and the near balletic interplay of electrical impulses and neurotransmitters that pulsate through it, is to monitor networks of neurons. Trying to understand how the brain works one neuron at a time is like attempting to decipher the mechanisms of a computer one transistor at a time.

"We need to look at lots of neurons simultaneously," says Kewley. "Otherwise, we might miss detailed correlations. By looking at enough cells, we hope we'll begin to see some patterns and get an idea of how the different areas coordinate. There needs to be a lot of data collection to get any handle on how the system works."

These new detectors may represent the future. Many neurophysiologists expect silicon neural probes to be a dominant experimental tool in brain science in the years to come. What's learned from this developing technology, furthermore, may aid in the creation of a "neural prostheses" -- an artificial, electronic bridge that spans faulty neural pathways in those suffering from diseases and injuries of the central nervous system.

-- Linda Marsa