The Dendrite That Decides

A new study in Science reveals that the apical tuft dendrites of layer 5 pyramidal neurons in the mouse motor cortex are specifically required for relearning complex behavioral rules, but not for executing already-learned behaviors or learning simpler rules. By activating a class of inhibitory neurons called NDNF interneurons that selectively target the dendritic tuft, researchers could block global calcium signaling in the dendrites and dramatically impair rule relearning, while local synaptic inputs remained intact. Excitatory synapses on the tuft formed functional clusters during complex rule performance, and NDNF interneurons themselves reduced their activity specifically during learning-related errors, suggesting they act as gatekeepers that open the dendrite to plasticity only when the brain needs to update a rule. Reference: Maristany de las Casas et al. (2026) "Tuft dendrites in frontal motor cortex enable flexible learning" Science 392, eadx4358. https://doi.org/10.1126/science.adx4358