Conceptual

Backpropagation, intuitively | Deep Learning Chapter 3

Backpropagation is a differentiable computational mechanism for calculating gradients in multi-layer neural networks by recursively applying the chain rule to decompose global cost sensitivities into local weight and bias updates. The theory formalizes learning as an optimization process where adjustments are proportional to both activation magnitudes and error signals, effectively implementing a biological "fire-together-wire-together" principle within a stochastic gradient descent framework to minimize empirical risk over high-dimensional parameter spaces.