Fig. 2.

Effects of STN DBS on willingness of the animals to produce an effort to obtain food or cocaine. Behavioral performances on the progressive ratio task illustrated as the mean number of rewards obtained (Upper) and the mean breaking point (i.e., last ratio reached) (Lower) for food reward (A) and for i.v. cocaine (B) in rats ON (black bars; n = 14 and 9 for A and B respectively) and OFF STN DBS (white bars; n = 8 and 9 for A and B respectively). Error bars illustrate standard errors (SEM). *P < 0.05 (ANOVA group effect), significant difference between groups STN DBS OFF and STN DBS ON.