Stimulus presentation can enhance spiking irregularity across subcortical and cortical regions

Stimulus presentation is believed to quench neural response variability as
measured by fano-factor (FF). However, the relative contribution of
within-trial spike irregularity and trial-to-trial rate variability to FF
reduction has remained elusive. Here, we introduce a principled approach
for accurate estimation of spiking irregularity and rate variability in
time for doubly stochastic point processes. Consistent with previous
evidence, analysis showed stimulus-induced reduction in rate variability
across multiple cortical and subcortical areas. However, unlike what was
previously thought, spiking irregularity, was not constant in time and
could be enhanced partly due factors beyond local CV measures such as
bursting abating the quench in the post-stimulus FF. Simulations confirmed
plausibility of a time varying spiking irregularity arising from within
and between pool correlations of excitatory and inhibitory neural inputs.
By accurate parsing of neural variability, our approach reveals previously
unnoticed changes in neural response variability and constrains candidate
mechanisms that give rise to observed rate variability and spiking
irregularity within brain regions.