## Predictive Coding has been unified with Backpropagation

“The backpropagation algorithm has three steps.

- Flow information forward through a network to compute a prediction.
- Compute an error by comparing the prediction to a target value.
- Flow the error backward through the network to update the weights.

The backpropagation algorithm requires information to flow forward and backward along the network. But biological neurons are one-directional.

[…]

The authors have unified predictive coding and backpropagation into a single theory of neural networks. Predictive coding and backpropagation are separate hardware implementations of what is ultimately the same algorithm.”