Department of Neurology, University of Lübeck, D-23538 Lübeck, Germany.
Institute for Robotics and Cognitive Systems, University of Lübeck, D-23538 Lübeck, Germany.
Neuropsychologia. 2019 Mar 4;125:109-115. doi: 10.1016/j.neuropsychologia.2019.01.016. Epub 2019 Feb 2.
Although an enhancing effect of reward on cognitive performance has been observed consistently, its neural underpinnings remain elusive. Recent evidence suggests that the inferior frontal junction (IFJ) may be a key player underlying such an enhancement by integrating motivational processes and cognitive control. However, its exact role and in particular a potential causality of IFJ activation is still unclear. In the present study, we therefore investigated the causal contributions of the left IFJ in motivated task switching by temporarily disrupting its activity using continuous theta burst stimulation (cTBS, Exp.1) or 1 Hz repetitive transcranial magnetic stimulation (rTMS, Exp.2). After TMS application over the left IFJ or a control site (vertex), participants performed a switch task in which numbers had to be judged by magnitude or parity. Different amounts of monetary rewards (high vs low) were used to manipulate the participants' motivational states. We measured reaction times and error rates. Irrespective of TMS stimulation, participants exhibited slower responses following task switches compared to task repeats. This effect was reduced in high reward trials. Importantly, we found that disrupting the IFJ improved participants' behavioral performance in the high reward condition. For high reward trials exclusively, error rates decreased when the IFJ was modulated with cTBS or 1 Hz rTMS but not after vertex stimulation. Our results suggest that the left IFJ is causally related to the increase in cognitive performance through reward.
虽然一直观察到奖励对认知表现有增强作用，但它的神经基础仍然难以捉摸。最近的证据表明，下额前回（IFJ）可能是通过整合动机过程和认知控制来增强这种作用的关键因素。然而，其确切的作用，特别是 IFJ 激活的潜在因果关系仍不清楚。在本研究中，我们通过使用连续 theta 爆发刺激（cTBS，实验 1）或 1 Hz 重复经颅磁刺激（rTMS，实验 2）暂时干扰其活动，来研究左 IFJ 在动机性任务转换中的因果贡献。在 TMS 应用于左 IFJ 或对照部位（顶点）之后，参与者执行了一项需要根据大小或奇偶性判断数字的切换任务。使用不同数量的金钱奖励（高或低）来操纵参与者的动机状态。我们测量了反应时间和错误率。无论 TMS 刺激如何，与任务重复相比，参与者在任务转换后反应较慢。这种效应在高奖励试验中减少。重要的是，我们发现干扰 IFJ 可以改善参与者在高奖励条件下的行为表现。仅在高奖励试验中，当使用 cTBS 或 1 Hz rTMS 调制 IFJ 时，错误率会降低，但在顶点刺激后不会降低。我们的结果表明，左 IFJ 通过奖励与认知表现的提高存在因果关系。
