get an error map and then we send that forward to the next layer and then we have a recurrent layer at each at each stage of the hierarchy that's trying to build up this prediction and it can get feedback just the same as in the brain and it can also get local recurrence and then you basically just subtract off and there's different ways you can do the subtraction doesn't much matter and then you get these errors you only send the errors forward through the network so one nice thing about this is at time one