Now we have something called a "memtransistor". We also have something called a "memristor".

But invariably in these discussions, there's another device that exists that almost never seems to get a mention. It's called a "memistor":

https://en.wikipedia.org/wiki/Memistor

It was first developed in 1960, and used for a couple of related hardware neural network architectures - ADALINE and MADALINE.

What is also interesting about this device, is that it can be relatively easily built by a hobbyist, as shown by:

http://www-isl.stanford.edu/~widrow/papers/t1960anadaptive.p...

Strangely, though - the memistor is hardly ever mentioned; it does have some downsides (mainly difficulty to miniaturize), so maybe that's it? Maybe somebody here can play with it...

Interestingly, on a side note - it's possible to homebrew a memristor as well:

http://sparkbangbuzz.com/memristor/memristor.htm