> IMO the much more likely explanation is that the brain uses contrastive learning somewhere. [...] Instead of using calculus and outer products to calculate derivatives, you feed real data and false data forward through the network and each neuron tracks and trains on the difference.
That's a technique that was tried in machine learning and worked (although obviously not optimally or we'd all be using it by now) and then we hypothesised that animal brains use it because it would explain sleep.
