Dendrites Carry Tailored Teaching Signals for Brain Learning

A Nature study using a neurofeedback brain–computer interface in mice shows distal dendrites of layer-5 cortical neurons carry vectorized, neuron-specific teaching signals that encode reward and task error separate from somatic activity. These somato-dendritic residuals predict learning, and disrupting dendritic signals (via anaesthesia or layer-1 interneuron activation) impairs learning, providing the first biological evidence for a vectorized credit-assignment mechanism in the brain that parallels ideas from artificial learning systems.