A MICROCHIP that uses chemicals instead of pulses of electricity to stimulate neurons has been created. It could open the way to implants that interact with our nervous system in a far more subtle way than is possible now.

While electrical pulses convey impulses along neurons, the cells communicate with each other and with other cells such as muscles by releasing chemical messengers. These neurotransmitters are released from one side of a cell junction, or synapse, and picked up by receptors on the other side, triggering another electrical pulse.

Since synapses are typically around 50 nanometres across, and each chemical puff contains just a few thousand molecules, building an artificial synapse is a huge challenge. But Mark Peterman and Harvey Fishman at Stanford University in California are getting close. They told a biophysics conference in Texas earlier this month that they have created four "artificial synapses" on a silicon chip ...