Voltage dynamics of cortical dendrites in vivo

Abstract

Voltage dynamics in dendrites, which result both from integrating synaptic inputs and back-propagating action potentials (bAPs) from the soma, contribute to plasticity. Mapping these dynamics in the dendritic arbors of live animals is crucial for understanding neuronal computation and plasticity rules. Here we combine targeted channelrhodopsin activation with dual-plane structured illumination voltage imaging for simultaneous monitoring of dendritic and somatic voltage response dynamics in cortical layer 2/3 pyramidal neurons in anesthetized and awake mice. We examined the integration of synaptic inputs and compared the dynamics of optogenetically evoked, spontaneous and sensory-evoked subthreshold and bAP dynamics. Our measurements revealed a broadly correlated membrane voltage throughout the dendritic arbor and only weak signatures of electrical compartmentalization within individual dendritic branches. However, we observed strong spiking-history-dependent modulation of bAP propagation into distal dendrites. We propose that this dendritic filtering of bAPs may have a critical role in the regulation of bursting and in activity-dependent plasticity.