Tiny changes in the way electrical signals move through neurons are the basis of learning and memory--and of many brain pathologies. But it has been difficult for neuroscientists to observe these changes in much detail. Now, researchers at Harvard University have created a tool with unmatched sensitivity: silicon nanowires that amplify very small electrical signals from as many as 50 places on a single neuron. Existing methods can pick up signals from only one or two places.

Chemist Charles Lieber and coworkers assemble nano­wires on a silicon chip, deposit electrical leads that connect to them, and add protein molecules that promote and control neuron growth. Finally, they seed the chip with rat neurons and wait four to ten days for them to grow. The proteins provide a path for the neuron's growth along the chip, ensuring that it makes contact with the nanowires. The technology could eventually help brain scientists understand the underpinnings of learning, memory, and disease.