Sodium pumps adapt spike bursting to stimulus statistics

Abstract

Pump activity is a homeostatic mechanism maintaining ionic gradients. Here we test whether the slow reduction in excitability induced by sodium pump activity seen in many neuronal types can also play a role in neuronal coding. We record intracellularly from a spike bursting sensory neuron in response to naturalistic stimulation using different statistical distributions. We show that the regulation of excitability by sodium pumps is necessary for the neuron to respond differently depending on the statistical context of stimuli. In particular, sodium pump activity allows spike burst sizes and rates to code not for stimulus values per se but their ratio with the standard deviation of the stimulus distribution. Modeling further shows that sodium pumps can be a general mechanism of adaptation to statistics in the time scale of a minute. These results implicate the ubiquitous pump activity in the adaptation to statistics in neural codes.