The John B. Pierce Laboratory New Haven, CT, USA.
Front Integr Neurosci. 2010 Oct 8;4:124. doi: 10.3389/fnint.2010.00124. eCollection 2010.
Previous studies by our lab and others have established a role for medial areas of the prefrontal cortex (mPFC) in the top-down control of action during simple reaction-time (RT) tasks. However, the neural circuits that allow mPFC to influence activity in the motor system have remained unclear. In the present study, we used a combination of tract-tracing and reversible inactivation methods to examine the role of a motor-related area in the rat frontal cortex, called the rostral forelimb area (RFA), in the top-down control of action. Neural tracing studies involved used electrical microstimulation to identify RFA and injections of biotinylated dextran amines (BDA) to map out connections of RFA with other parts of the frontal cortex. Connections were found between RFA and mPFC, the agranular insular cortex, and the primary motor cortex. Reversible inactivations using muscimol infusions into RFA increased response times and eliminated delay-dependent speeding, but did not increase premature responding. These results are markedly different from what is obtained when muscimol is infused into mPFC, which leads to excessive premature responding and a reduction of RTs to stimuli at short delays (Narayanan et al., 2006). We also tested animals during the RT task after inactivating the agranular insular cortex, which contains neurons that projects to and receives from RFA and mPFC, and found no effects on RT performance. Together, these studies suggest that RFA is a premotor region in the rat frontal cortex that competes with mPFC to control action selection. We suggest that RFA controls the threshold that is used to initiate responding and generates prepotent excitation over responding that is crucial for temporal preparation.
先前，我们实验室和其他实验室的研究已经确定了前额叶皮层（mPFC）内侧区域在简单反应时（RT）任务中对动作的自上而下控制中的作用。然而，mPFC 影响运动系统活动的神经回路仍不清楚。在本研究中，我们使用追踪和可逆失活方法的组合，检查了大鼠前额叶皮层中一个与运动相关的区域，称为前肢区（RFA），在动作的自上而下控制中的作用。神经追踪研究使用电微刺激来识别 RFA，并注射生物素化葡聚糖胺（BDA）以绘制 RFA 与前额叶皮层其他部分的连接图。发现 RFA 与 mPFC、无颗粒岛叶皮层和初级运动皮层之间存在连接。使用 RFA 中的 muscimol 输注进行可逆失活会增加反应时间并消除延迟相关的加速，但不会增加过早反应。这些结果与 muscimol 输注到 mPFC 时获得的结果明显不同，输注到 mPFC 会导致过度过早反应和缩短短延迟刺激的 RT 减少（Narayanan 等人，2006 年）。我们还在失活无颗粒岛叶皮层后在 RT 任务期间测试了动物，该皮层包含投射到 RFA 和 mPFC 并从中接收信息的神经元，并且发现对 RT 性能没有影响。总之，这些研究表明，RFA 是大鼠前额叶皮层中的一个前运动区域，与 mPFC 竞争以控制动作选择。我们认为，RFA 控制用于启动反应的阈值，并产生对时间准备至关重要的强烈反应的优势兴奋。
