Figure 5.

In whole ensembles, ketamine also weakened the SNR for rules via both a reduction in signal and an increase in noise. A, Considering correct trials only, the SNŖ measured as the Mahalanobis distance (D_Mah) between neural correlates of the two rules, remained unchanged by acute ketamine administration (white bar, before injection; black bar, after injection). Gray dots indicate values of individual data points. B, When all trials were considered, the ensemble SNR was significantly compromised by ketamine administration. C, Considering correct trials only, the rule signal, defined as the Euclidean distance (D_Euc) between ensemble activities associated with the two rules, remained unchanged by ketamine. D, When error trials were also included, however, the signal was weakened after ketamine injection. E and F consider correct trials only. E, The total variance, part of the noise factored into the ensemble SNR calculation, was significantly enhanced by ketamine injection (left vs right bars) to the same extent in both task rules (gray vs black bars). F, The averaged correlation coefficient, which is another contributing factor to ensemble SNR, was not changed by ketamine (left vs right bars) regardless of the task rule (gray vs black bars). G and H consider all trials, including errors. G, The total variance was enhanced by ketamine injection (left vs right bars) to the same extent in both task rules (gray vs black bars). H, The averaged correlation coefficient remained unchanged after ketamine administration (left vs right bars) in both prosaccade and antisaccade trials (gray vs black bars). *p < 0.05, **p < 0.005, ***p < 0.0001.