Attempts to simulate the brain usually involve programming software to behave like groups of neurons. A new "neuromorphic" design instead tries to recreate the brain's hardware, using analogue components last seen in the early days of computing. "On our system, you can physically point to the neuron," says Karlheinz Meier of the University of Heidelberg in Germany.
The Spikey chip contains 400 "neurons", or printed circuits. Real neurons have a voltage across their outer membrane, which Spikey mimics using capacitors: components that store charge. Just as in a real neuron, when the applied voltage reaches a certain level, the capacitor becomes conductive, firing a "nerve signal".
Spikey also mimics synapses - the connections between neurons. In a normal chip, every process is digital and so can only take the value 0 or 1. Meier's team instead used analogue components with variable levels of resistance to simulate the way connections between neurons become stronger or weaker depending on how much they are used. "Analogue circuits died after digital computers became more powerful," says Meier, but they are now finding new roles.
