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. 2017 Dec 23;6:e29226. doi: 10.7554/eLife.29226

Figure 5. Cortical state influences the information encoded in population activity.

(A) The probability of correct classification (PCC) as a function of population size. PCC was significantly higher in the low pre-stimulus case (F(1,164)=9.32; p<0.005; two-way repeated measures ANOVA). (inset) The difference in classification performance between low and high pre-stimulus response states for a small (n = 2, orange) and a large population (n = 12, blue). The performance difference was greater for the larger neural population (p<0.05, bootstrap test). (B) Noise correlations of evoked responses for the high and low pre-stimulus states – correlations were significantly higher in the high pre-stimulus state (p=7.918e-10; paired t-test). (C) Probability of correct classification for the two cortical states. ‘With correlations’ represents data using the following equation: d2= ΔμTQ1Δμ; Probability of correct classification = erfc(d2)/2. ‘Without correlations’ represents the probability of correct classification when ignoring the effect of noise correlations using (dshuffled2=ΔμTQd1Δμ), where Qd is the diagonal covariance matrix. In each condition there is a statistically significant difference between the high and low pre-stimulus conditions (*p<0.05; paired t-test). (D) The magnitude of the difference in FLD means (left) and the magnitude of the pooled standard deviation (σ) of the FLD (right). In the low pre-stimulus condition, the difference in means was significantly greater (p<0.0001; paired t-test). The average variance was also higher in the low pre-stimulus condition (p<0.0001; paired t-test), but this had less overall impact on the population d’. The results in this figure were obtained for all the cells recorded across sessions for an orientation difference of ±5°.

Figure 5.

Figure 5—figure supplement 1. Probability of correct classification (PCC) as a function of population size when baseline-subtracted evoked responses to the target and test stimuli are used.

Figure 5—figure supplement 1.

PCC does not depend significantly on pre-stimulus activity for any population size (p>0.1; two-way repeated measures ANOVA).