RT Journal Article SR Electronic T1 Supralinear Ca2+ Influx into Dendritic Tufts of Layer 2/3 Neocortical Pyramidal Neurons In Vitro and In Vivo JF The Journal of Neuroscience JO J. Neurosci. FD Society for Neuroscience SP 8558 OP 8567 DO 10.1523/JNEUROSCI.23-24-08558.2003 VO 23 IS 24 A1 Jack Waters A1 Matthew Larkum A1 Bert Sakmann A1 Fritjof Helmchen YR 2003 UL http://www.jneurosci.org/content/23/24/8558.abstract AB Pyramidal neurons in layer 2/3 of the neocortex are central to cortical circuitry, but the intrinsic properties of their dendrites are poorly understood. Here we study layer 2/3 apical dendrites in parallel experiments in acute brain slices and in anesthetized rats using whole-cell recordings and Ca2+ imaging. We find that backpropagation of action potentials into the dendritic arbor is actively supported by Na+ channels both in vitro and in vivo. Single action potentials evoke substantial Ca2+ influx in the apical trunk but little or none in the dendritic tuft. Supralinear Ca2+ influx is produced in the tuft, however, when an action potential is paired with synaptic input. This dendritic supralinearity enables layer 2/3 neurons to integrate ascending sensory input from layer 4 and associative input to layer 1.