Something was missing.

Since electronics was developed, engineers have made circuits using combinations of three basic elements – resistors, capacitors and inductors.

But in 1971, a young circuit designer called Leon Chua at the University of California, Berkeley, realised something was missing. He was toying with the non-linear mathematics that describes how the four variables in a circuit – voltage, current, charge and flux – behave in the three basic elements.

The three building blocks each relate two of the four electronic properties of circuits, creating a chain linking charge to flux via voltage and current. But his calculations showed there should be a fourth device to directly link flux and charge.

But, no one could make such devices and the idea was mostly forgotten. . . until some fellows worked out why their work to develop titanium dioxide memory circuits was glitchy.

. . . these efforts have been dogged by bizarre electronic effects, says Williams, who has now worked out the reason. His titanium dioxide works as a memoristor – the mythical device has been found. . .

The way memristors handle current and voltage is startlingly similar to the way synapses between brain cells do, says Chua. Both build up voltage to a threshold before firing and letting a current pass.

Williams agrees. "The memristor equations do a very good job of modelling the known behaviour of synapses," he says.

I could use a little prosthetic help for my high mileage brain. They say it's the second thing to go.