Spontaneous quasi-oscillations modulate intrinsic shot noise-like events in electrosensory pyramidal neurons.

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. 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, sponataneous quasi-oscillations. This cross-relation is evidence that, at the single-neuron level, intrinsic membrane potential dynamics can exhibit a form of phase-amplitude coupling. With computational models of neuronal dynamics, we further investigate the potential role of this cross-relation on electrosensory processing, particularly with respect to the detection of weak sensory input. We hypothesize that top-down signals can adjust the phase of the quasi-oscillations such that the peak of neuronal excitability is aligned with the arrival of sensory information. Our results highlight that neurons can spontaneously display rich intrinsic behaviour, which is likely to impact how they process synaptic input.