croehrig
Someone here likened it to how programs can move around in computer memory. If neurons are the "silicon of the brain" or the "PHY" layer, the biggest problem in neuroscience IMHO is that we have virtually no understanding of what is the next layer up, (i.e. the "logical layer"). What is the equivalent of program counters, CPU instructions, etc. in the brain?
The brain is a nonlinear recurrent dynamical system and we are really in the dark as to how to break the dynamics down into understandable subcomponents.
To get an idea of the complexity, this paper by Randall Beer analyzes the possible behaviours of 1 and 2 neuron circuits:
Beer, R. D. (1995). On the Dynamics of Small Continuous-Time Recurrent Neural Networks. Adaptive Behavior, 3(4), 469–509. doi:10.1177/105971239500300405
Obviously this kind of analysis doesn't scale to 10^10 neurons.
It doesn't work all the time as the previous poster noted, but it is very low friction which is especially important when writing quick throw-away scripts.