Slow Conductances Encode Stimulus History into Spike Shapes

Abstract

The shape of action potentials plays an important role in synaptic integration. Action potentials of different shapes shunt excitatory potentials differentially and consequently correspond to different probabilities of generating the next spike. Thus two neurons producing different spikes shapes, say Purkinje and pyramidal cells, integrate differently the same excitatory potentials. More interestingly, there is variability in the spike shape of a single neuron when stimulated dynamically, that can then also dynamically affect the synaptic integration. Our recent experiments have shown that this variability in the spike shape is not random but depends on stimulus history. Here we analyze a simple model of cortical neuron to understand the origin of this encoding of stimulus history into spike shape. We find that slow conductances, for example calcium conductances, can be responsible for this rich encoding.