Figure 10.
Noise correlation reduces the information efficiency. a, Mutual information for simultaneously recorded single neurons (abscissa) compared with the mutual information for the shuffled responses (ordinate) for each session. The shuffling procedure was repeated 50 times, and the average mutual information value was plotted as MItrial-shuffled. Each line connects different population sizes within a session. Multiple levels of brightness are used for better visibility. For each population size, the information content of all possible selections of that size was averaged within session. Error bars indicate the standard error of means. b, Solid lines with circles as marker indicate mutual information for the simultaneously recorded neural responses (carried over from Fig. 6). Dashed lines with triangles as marker indicate mutual information for the same neuronal responses, but now with a shuffled trial structure. Error bars are the standard error of means across eight recording sessions. c, The percentage improvement in mutual information after shuffling as a function of pool size. d, Mutual information between stimuli and pooled neuronal response across all sessions. Trials of the simultaneously recorded neurons were shuffled to remove noise correlation. For each population size, the information content of 1000 random selections of that size was averaged. This was done with the exception of the population sizes of 1, 72, and 73 neurons, where the number of possible selections was limited to 73, 73, and 1, respectively. The data points after the break in the abscissa includes multiunit clusters with the single-unit data to provide the full population response across all sessions (n = 16). From the firing rates, we estimate that the total population consisted of ∼215 single units.