the brains of an amoeba

Amoeba memory? Maybe.

Di Ventra's team thinks there is an intrinsic memory storage device within the amoeba. As with the human brain, that device can strengthen and store memories for some time. But if the memory isn't used, it gradually fades away.

Now they have identified a potential storage device. The amoeba's interior contains a watery sol – a solid suspended in liquid – within a thick viscous gel. The sol flows through the gel like water through a sponge, creating a network of low-viscosity channels. Those channels are strengthened as long as the amoeba continues to respond to a static environment, but if that environment changes the channels gradually break down and a new network appears as the amoeba adapts. For a short while, though, the amoeba retains a “memory” of those earlier conditions.

Di Ventra's team took advantage of the development this year of memristors – electrical resistors that retain a memory of earlier voltages or currents applied and vary their resistance accordingly – to design a simple circuit that models the amoeba's gel-sol system. Their circuit contained just four basic elements: a resistor, capacitor, inductor and memristor. By changing the external voltage in a regular way they could model the changing temperature conditions studied by Nakagaki's team. When they did this, they found that their circuit could “learn” and predict future voltage fluctuations.

Earlier this year, I linked to the very same article in the blockquote, citing this passage:

Chua, now close to retirement, is thrilled at the finding.... "We can now expect many new unconventional applications, including super-dense memories and brain-like computing chips."

I wonder if Chua expected an amoeba to take the lead.