Fig. 4.
Effect of noise correlations. (A) Correlation coefficient matrices. Dark values indicate high correlations. Neurons are arranged according to their preferred orientation, so correlations between cells with similar tuning properties are close to the main diagonal. Diagonal entries have been removed for visualization. (B–D) MASE, MMSE, and IMDE for a population of n = 100 neurons for the four different noise correlation structures shown relative to the independent population in logarithmic units. Colors are as shown in A. (E and F) MASE (dashed lines) and IMDE (solid lines) for a population of 100 neurons with stimulus-dependent (red) or uniform correlations (blue) at 500 ms (E) and 10 ms (F) as a function of average correlation strength. Data are shown relative to the independent population in logarithmic units. (G and H) Neurometric functions for the four correlation structures at 500 ms (G) and at 10 ms (H). The square marks Δθc; from there on stimulus-dependent correlations perform worse than uniform correlations. In H, the crossing point lies effectively at Δθ = 0. Data are also shown relative to the independent population, smoothed and in logarithmic units on the y axis in the Insets.