experiments here that show this so this gives you very good evidence that if the hidden representations they look as if they had been computed by backdrop and not by any of these scaler update algorithms so it is conceivable that we find backprop in the brain that's why they go here next they go into problems with backdrops so basically why why would we why so far have we believed that back prop isn't happening in the brain so now let's I want to highlight two factors here that that I find a thinker suffice state they have more but first