Dept. of Neurology, University Clinic Leipzig, Germany.
Neuroimage. 2011 Jul 15;57(2):617-23. doi: 10.1016/j.neuroimage.2011.04.038. Epub 2011 Apr 30.
The prefrontal cortex is known to play a key role in higher-order cognitive functions. Recently, we showed that this brain region is active in reinforcement learning, during which subjects constantly have to integrate trial outcomes in order to optimize performance. To further elucidate the role of the dorsolateral prefrontal cortex (DLPFC) in reinforcement learning, we applied continuous theta-burst stimulation (cTBS) either to the left or right DLPFC, or to the vertex as a control region, respectively, prior to the performance of a probabilistic learning task in an fMRI environment. While there was no influence of cTBS on learning performance per se, we observed a stimulation-dependent modulation of reward vs. punishment sensitivity: Left-hemispherical DLPFC stimulation led to a more reward-guided performance, while right-hemispherical cTBS induced a more avoidance-guided behavior. FMRI results showed enhanced prediction error coding in the ventral striatum in subjects stimulated over the left as compared to the right DLPFC. Both behavioral and imaging results are in line with recent findings that left, but not right-hemispherical stimulation can trigger a release of dopamine in the ventral striatum, which has been suggested to increase the relative impact of rewards rather than punishment on behavior.
前额皮质被认为在高阶认知功能中发挥着关键作用。最近，我们发现这个脑区在强化学习中是活跃的，在此过程中，被试者必须不断整合试验结果，以优化表现。为了进一步阐明背外侧前额皮质（DLPFC）在强化学习中的作用，我们分别在执行 fMRI 环境中的概率学习任务之前，对左侧或右侧 DLPFC 或顶点（作为对照区域）应用连续 theta 爆发刺激（cTBS）。虽然 cTBS 本身对学习表现没有影响，但我们观察到刺激对奖励与惩罚敏感性的调节作用：左半球 DLPFC 刺激导致更具奖励导向的表现，而右半球 cTBS 诱导更具回避导向的行为。FMRI 结果显示，在接受左侧而非右侧 DLPFC 刺激的受试者中，腹侧纹状体的预测误差编码增强。行为和成像结果均与最近的发现一致，即左侧而非右侧刺激可以引发腹侧纹状体多巴胺的释放，这被认为增加了奖励对行为的相对影响，而不是惩罚。
