Normalization is shared between neurons and reduces noise correlation. a, Histogram of correlation coefficients of the inferred single-trial denominator for pairs of simultaneously recorded neurons with similar tuning. Gray bars: pairs with non-significant correlation; black bars: pairs with significant correlation. Triangle: average correlation across all pairs. b, Black symbols and gray shaded area: Median noise correlation and 95% CI, as a function of the average normalization strength of each pair. For each pair, the inferred values of D of each neuron were z-scored across trials; then trials were sorted by the average z-scored D of the pair. Each point in the plot represents averages computed in windows of 12 trials. Yellow area: 95% CI for a control with trial order shuffled independently for each neuron, to remove noise correlations. c, Histogram of noise correlation coefficients during trials with large (blue) or small (red) inferred normalization signal. These estimates of correlations are based on few trials (as little as 5 in some cases, see related text), hence the large range of values. Triangles denote group medians.