Intrinsic voltage fluctuations reveal a form of phase-amplitude coupling in electrosensory pyramidal neurons.

Abstract

The stochastic flickering of ion channels is known to cause ongoing membrane potential fluctuations in neurons. This channel noise is often considered negligible in comparison to synaptic noise, yet it can shape the integrative properties of neurons. Here, in vitro recordings of electrosensory pyramidal neurons under synaptic blockade are characterized and shown to contain a non-trivial repertoire of dynamical features. Our analyses reveal an intrinsic noise structure that is much richer than what could be expected based on previous studies: we identify rapid, small-amplitude, shot noise-like events and we quantify how their rate and amplitude are modulated by slower, large-amplitude fluctuations. This cross-relation is evidence that, at the single-neuron level, membrane potential dynamics can exhibit a form of phase-amplitude coupling. We also investigate the appearance of fast, intermittent subthreshold oscillations and conclude that they are manifestation of stochastic linear dynamics, possibly with time-varying parameters. Our results, collectively, highlight that neurons can spontaneously display rich intrinsic behaviour, which is likely to impact how they process synaptic input.