Division of Neurotoxicology, National Center for Toxicological Research.
Exp Clin Psychopharmacol. 2011 Apr;19(2):145-53. doi: 10.1037/a0022794.
The effects of methylphenidate (MPH) on motivation were examined using a progressive ratio (PR) task in children who were prescribed MPH for the treatment of ADHD. Twenty-one children, 7 to 12 years of age, completed two test sessions, one under the effects of medication and one not. During each session, children pressed a lever to earn nickel reinforcers, where the first press resulted in a reinforcer and 10 additional presses were required for each subsequent reinforcer. Children on MPH had a significantly higher breakpoint than when off medication. This MPH-associated increase in the breakpoint manifested as a significant decrease in the interresponse times (IRT). Further, MPH administration resulted in a significant decrease in IRT variability. In contrast, MPH administration had no significant effects on the means and variability of postreinforcement pause duration. These results suggest that MPH increased motivation in children being treated for ADHD. Further, the inability of MPH to significantly reduce postreinforcement pause duration while simultaneously decreasing IRTs suggests that while MPH may increase motivation to perform an ongoing task, it may have little effect on the initiation of that task.
使用递增比率（PR）任务研究了哌醋甲酯（MPH）对动机的影响，该任务适用于因 ADHD 而开处方 MPH 的儿童。21 名 7 至 12 岁的儿童完成了两次测试，一次在药物作用下，一次不在药物作用下。在每次会议期间，孩子们按下杠杆以获得镍强化物，第一次按下会产生强化物，而随后的每次强化物需要额外按下 10 次。服用 MPH 的儿童的断点明显高于未服用药物时的断点。MPH 相关的断点增加表现为反应时间（IRT）显著减少。此外，MPH 给药导致 IRT 变异性显著降低。相比之下，MPH 给药对强化后停顿时间的平均值和变异性没有显著影响。这些结果表明，MPH 增加了接受 ADHD 治疗的儿童的动机。此外，MPH 虽然能显著减少 IRTs，但不能显著减少强化后停顿时间，这表明虽然 MPH 可能会增加对正在进行的任务的动力，但对该任务的启动可能几乎没有影响。
