Distributed coding of evidence accumulation across the mouse brain using microcircuits with a diversity of timescales

The gradual accumulation of noisy evidence for or against options is the main step in the perceptual decision-making process. Using brain-wide electrophysiological recording in mice (Steinmetz et al., 2019), we examined neural correlates of evidence accumulation across multiple brain areas. We demonstrated that the neurons across the brain exhibited ramping-like firing rate activity that was modulated by the strength of evidence. These neurons had distinct properties in their intrinsic timescale, which were organized hierarchically across the brain. Our findings support the existence of evidence accumulation over multiple timescales. Besides variability across brain regions, a heterogeneity of intrinsic timescales was observed within each brain region as well. We demonstrated that this variability reflected the heterogeneity of microcircuit accumulation parameters, such that populations with longer timescales had higher recurrent excitation strength.