Population-Level Neural Codes Are Robust to Single-Neuron Variability from a Multidimensional Coding Perspective

•Correlated trial-by-trial variability can impair the reliability of neural codes•Multidimensional codes of stimulus orientation are highly stable over weeks•Multidimensional correlations restrict variability to non-coding directions•Up to 50% of single-trial, single-neuron “noise” is predictable with correlations

SummarySensory neurons are often tuned to particular stimulus features, but their responses to repeated presentation of the same stimulus can vary over subsequent trials. This presents a problem for understanding the functioning of the brain, because downstream neuronal populations ought to construct accurate stimulus representations, even upon singular exposure. To study how trial-by-trial fluctuations (i.e., noise) in activity influence cortical representations of sensory input, we performed chronic calcium imaging of GCaMP6-expressing populations in mouse V1. We observed that high-dimensional response correlations, i.e., dependencies in activation strength among multiple neurons, can be used to predict single-trial, single-neuron noise. These multidimensional correlations are structured such that variability in the response of single neurons is relatively harmless to population representations of visual stimuli. We propose that multidimensional coding may represent a canonical principle of cortical circuits, explaining why the apparent noisiness of neuronal responses is compatible with accurate neural representations of stimulus features.

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