“a consensus has emerged that the brain cannot directly implement backprop, since to do so would require biologically implausible connection rules”
There’s no such emerging consensus, that’s actually from F. Crick’s personal opinions in the nineties. Here’s a more recent take:
https://www.cell.com/trends/cognitive-sciences/fulltext/S1364-6613(19)30012-9?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS1364661319300129%3Fshowall%3Dtrue
There’s no such emerging consensus, that’s actually from F. Crick’s personal opinions in the nineties. Here’s a more recent take:
https://www.cell.com/trends/cognitive-sciences/fulltext/S1364-6613(19)30012-9?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS1364661319300129%3Fshowall%3Dtrue