The Nature of Shared Cortical Variability

I-Chun Lin,Michael Okun,Matteo Carandini,Kenneth D Harris

doi:10.1016/j.neuron.2015.06.035

Abstract

SummaryNeuronal responses of sensory cortex are highly variable, and this variability is correlated across neurons. To assess how variability reflects factors shared across a neuronal population, we analyzed the activity of many simultaneously recorded neurons in visual cortex. We developed a simple model that comprises two sources of shared variability: a multiplicative gain, which uniformly scales each neuron’s sensory drive, and an additive offset, which affects different neurons to different degrees. This model captured the variability of spike counts and reproduced the dependence of pairwise correlations on neuronal tuning and stimulus orientation. The relative contributions of the additive and multiplicative fluctuations could vary over time and had marked impact on population coding. These observations indicate that shared variability of neuronal populations in sensory cortex can be largely explained by two factors that modulate the whole population.

Highlights

Repeated presentations of the same stimulus elicit highly variable responses in sensory cortex (Heggelund and Albus, 1978; Tolhurst et al, 1983; Vogels et al, 1989)
Neuronal responses of sensory cortex are highly variable, and this variability is correlated across neurons
We developed a simple model that comprises two sources of shared variability: a multiplicative gain, which uniformly scales each neuron’s sensory drive, and an additive offset, which affects different neurons to different degrees

Summary

Introduction

Repeated presentations of the same stimulus elicit highly variable responses in sensory cortex (Heggelund and Albus, 1978; Tolhurst et al, 1983; Vogels et al, 1989). This variability is correlated across neurons, so it cannot be removed by averaging across the population, and may place critical constraints on information transmission (Averbeck et al, 2006; Averbeck and Lee, 2006; Deweese and Zador, 2004; Shadlen and Newsome, 1998; Zohary et al, 1994). Variability has been studied in single neurons or neuronal pairs, but a full description requires understanding factors operating at the population level

Results

Discussion

Conclusion