I am working between machine learning and neuroscience, and find such explanations really interesting, so thank you. I would agree that there is currently not a

I am working between machine learning and neuroscience, and find such explanations really interesting, so thank you. I would agree that there is currently not a lot of evidence that non-local learning such as backpropagation happens in the brain (event though there are some papers trying to find this evidence). But what you describe still falls into the Hebbian principle ("fire together - wire together") right? And this is still one idea originally engrained in perceptrons. While the brain's local learning algorithm is unknown and would be important to know for machine learning, e.g. to get ahead with unsupervised learning, there is quite some recent evidence that machine learning people are on the right track, at least with what deep convolutional neural networks learn in their hierarchy.