Catching up with the brain...

Kwabena Boahen looks to create a computer to act like a brain.  In his discussion
Mr. Boahen describes how the transistor is like a neuron.  However, what is keeping
us from making a synthetic neuron and using that on a processor?  Or using it to
store data?  This is kind of what I was talking about when I mentioned bio computing,
but I want to use synthetic anatomy and physiology as a computer.