L-DOPA administration modifies activity of striatal projection neurons. A, Response accuracy (left), reaction times (middle), and running times (right) during last five overtraining (OT; light blue), saline (S; gray), and first five L-DOPA (light brown) sessions. Error bars indicate SEM. B, E, Ensemble activity of task-activated (B) and tonically task-suppressed (E) MSNs during the last five overtraining, saline, and first five L-DOPA sessions. Conventions are as in . C, F, Raw firing rates of task-activated (C) and task-suppressed (F) MSNs in the control (blue) and dopamine-depleted (red) striatum, averaged across last five overtraining sessions (left) and first five L-DOPA sessions (right). L-DOPA treatment reduced the enhanced pre-task activity of tonically suppressed MSNs (TS; arrow) but did not affect the dynamically suppressed (DS) MSN population. D, G, Pre-task and in-task firing rates of task-activated (D), tonically suppressed (G, top), and dynamically suppressed (G, bottom) MSNs, averaged over last five overtraining sessions and first five L-DOPA sessions. Asterisks indicate significant differences as in E. BL, baseline; WC, warning click; GO, gate opening; ST, start; TO, tone onset; TS, turn start; TE, turn end; and GR, goal-reaching.