Scientists have built the first "neurochip," a silicon chip equipped with living nerve cells. It could be a precursor to bionic devices made from silicon and living neurons. But for now, neurobiologists want to use the device for understanding how nerve cells grow and talk to each other.
Biologists have studied individual neurons for years, by inserting electrodes into living brains. But that's kind of like trying to learn electronics by taking apart a computer: In both cases, the student might do better by first constructing simple circuits.
Early efforts to link living neurons in the lab have damaged or killed the cells. But Jerome Pine, a neurophysicist at the California Institute of Technology in Pasadena, has managed to pull the trick off. At the meeting of the Society for Neuroscience in New Orleans last week, he described how his team of electrical engineers and biologists created a microscopic neural landscape on a 4-centimeter-wide silicon rectangle. The chip, immersed in a petri dish, had 16 tiny wells with short tunnels leading to the surface. The researchers placed an embryonic rat brain cell in each well. As the cells grew, they sent out dendrites that eventually wound their way through the tunnels (which kept the cells clamped in place) and contacted other dendrites, establishing normal electrical activity. Wires in the underlying silicon listened in on the chatter.
"Now," Pine says, "the biggest challenge is maintaining a healthy network." So far the researchers have been able to keep cells alive for only 2 weeks at a time. Once they can sustain cells longer, they hope to study, for example, how small groups of neurons "learn" after being stimulated repeatedly.
"The work will certainly be important for future medical applications," says Peter Fromherz, a neurophysicist at the Max Planck Institute for Biochemistry in Munich, Germany, who is also trying to marry neurons and silicon. The retina, because it's flat like a silicon chip, "may be the best system" to start with, he says. But it's not time yet to get excited about bionic chips, warns Pine: "You shouldn't expect anything in our lifetime."
