(A–D) Raster plots (A, B) and corresponding PSTHs (C, D) of two example units. Neural responses are aligned to the fixation (Fix), instruction (Inst), movement onset (Move), turn onset (Turn), and feedback (Fdbk). Each point in (A, B) represents an action potential. Significant differences (p<0.1) between pairs of PSTHs within each unit are indicated by corresponding pairs of colored stars. S and U indicate subject and unit identities, respectively, and Nt indicates the total number of trials per unit. (E–H) Projections of population responses on the top four principal components reveals distinct response patterns associated with different task events and trial types. Ns, Nu, and Nt indicate the number of subjects, units, and trials, respectively. Stars indicate Holm–Bonferroni corrected p<0.001 for pairwise permutation tests. Shadings in C–H are SE. Because there was no turn onset on reach trials, we sampled from the distribution of turn onset times on turn trials to create the turn-aligned PSTHs for reach trials (see Materials and methods).