[cbennett]

It's far from clear that STDP is sufficient to the brain's learning mechanisms, though it is certainly necessary at some scales and stages.

The possibility space between relatively simple and insufficiently general unsupervise/clustering approaches and rigid SGD schemes is large, and probably contains the brain's true inference engine. Personally, I am excited by some of the ideas brought forward in this Bengio paper: https://arxiv.org/pdf/1602.05179.pdf