Predictive Coding

Predictive coding can recover backpropagation gradients under appropriate conditions through local message passing. The article argues that prior assessments of predictive coding may have been distorted by the identity-precision simplification. Predictive coding is presented as a biologically grounded alternative to backpropagation that uses explicit prediction-error units, local energy minimisation, and Hebbian updates. Deep predictive coding has been limited by slow iterative inference and performance degradation with depth.