Dendritic coincidence detection in Purkinje neurons of awake mice

Dendritic coincidence detection is thought fundamental to neuronal processing, yet the underlying dendritic voltage-calcium relationship remains unexplored in awake animals. Here, using simultaneous voltage and calcium two-photon imaging of Purkinje neuron spiny dendrites, we show how coincident sub- and suprathreshold synaptic inputs modulate dendritic calcium signaling during sensory stimulation in awake mice. Sensory stimulation evokes subthreshold excitatory and inhibitory post-synaptic potentials, that coincide with suprathreshold dendritic spikes triggered by climbing fiber and parallel fiber synaptic input. Purkinje neuron dendrites integrate these inputs in a time-dependent and non-linear fashion to enhance the sensory evoked dendritic calcium signal. Intrinsic supra-linear dendritic mechanisms, including voltage gated calcium channels and metabotropic glutamate receptors, are recruited cooperatively to expand the dynamic range of sensory evoked dendritic calcium signals. This establishes how dendrites use multiple interplaying mechanisms to perform coincidence detection, as a fundamental and ongoing feature of dendritic integration during behavior.