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. 2014 Dec 17;40(5):1234–1242. doi: 10.1038/npp.2014.309

Figure 2.

Figure 2

Methamphetamine pretreatment led to an increase in medium-effort/reward (MER) choices in preference to low-effort/reward (LER) option, leaving high-effort/reward (HER) choices unaffected. Bar graphs represent percent HER, medium effort/reward (MER), and LER pre- (a) and post-treatment (b) +SEM. (a) There were no pre-existing group differences and no preference for any of the goal arms prior to treatment; all animals distributed their choices uniformly across the reward arms. (b) There was a strong post-treatment preference for the MER arm compared with the LER arm (p<0.01) in methamphetamine animals, which was not present in the saline-treated group. Methamphetamine-treated animals chose the MER option more frequently compared with the saline group (p<0.05), and shifted away from the LER option (p<0.01). Groups were not different on HER choices. Methamphetamine-pretreated animals shift away from LER immediately, whereas MER preference increases as a result of repeated training. (c) The shift-away from LER was present from the beginning of the post-treatment testing (starting day 1, p<0.01). (d) The MER choice increases became significant on day 3 (p<0.05). *p<0.05, **p<0.01.