Thanks.  I really need to read that paper.  I've been thinking quite a bit about backpropagation in neural networks lately, and how implausible it would be for a biological system to do it.   I'm hoping that neuroscience eventually gives us more information about brain micro-structure, which may give some hints as to what's really going on.  

And they don't really need to map the entire brain.  Getting good detail on the visual pathway would be a great start.  Then it would be nice to tie that into the part of the brain that holds onto a short term 3D model of our immediate surroundings to control body movement.  I'm convinced that the two are very tightly bound.  

On the topic of uploading one's brain into a machine, I'm relieved we are no where close to making that happen.  Besides, I can't think of a worse type of prison:  being able to think but not actively engage with one's surrounding environment.  Just ask someone with a significant physical disability (blindness, complete loss of muscle control) ... it's the terror of being "trapped inside."  And the whole idea reminds me of a particular H.P. Lovecraft short story that still gives me some anxiety.  LOL