Figure 7. Dose-dependent contraction of neural trajectories.

(A) Example of ACC neural trajectories before injection (left panel), and after injection of 0.5 mg/kg AMPH (right panel) plotted into the same low-dimensional space for one session. The volume enclosed by the envelope (outer hull) of the trajectories contracts after AMPH. (B) Post-AMPH changes in mean trajectory volume over all sessions and trials with large reward. The volume decreases for intermediate doses, and expands at the highest dose. (C) The same dose-dependent volume changes occur for small-reward trials. (D) Changes in the amount of variance explained by the first three factors after AMPH. Medians and 95% confidence intervals are shown, revealing that explained variance is not significantly reduced after AMPH because the confidence intervals encompass 0. (E) Change in SEM of neural trajectories after AMPH on large reward trials averaged over all the first three factors and all spatial bins, showing a reduction in trial-by-trial variance for low-dose AMPH. (F) Same as panel E for small reward trials. (G) Change in SEM for the first factor across task epochs. Data are averaged over all sessions with similar treatment for large reward trials. Asterisks (*) indicate statistically significant differences at p<0.05; only comparisons with vehicle are illustrated. Panels B, C, E, and F show means and SEM.