Department of Psychology, University of Amsterdam, The Netherlands.
Proc Natl Acad Sci U S A. 2010 Sep 7;107(36):15916-20. doi: 10.1073/pnas.1004932107. Epub 2010 Aug 23.
When people make decisions they often face opposing demands for response speed and response accuracy, a process likely mediated by response thresholds. According to the striatal hypothesis, people decrease response thresholds by increasing activation from cortex to striatum, releasing the brain from inhibition. According to the STN hypothesis, people decrease response thresholds by decreasing activation from cortex to subthalamic nucleus (STN); a decrease in STN activity is likewise thought to release the brain from inhibition and result in responses that are fast but error-prone. To test these hypotheses-both of which may be true-we conducted two experiments on perceptual decision making in which we used cues to vary the demands for speed vs. accuracy. In both experiments, behavioral data and mathematical model analyses confirmed that instruction from the cue selectively affected the setting of response thresholds. In the first experiment we used ultra-high-resolution 7T structural MRI to locate the STN precisely. We then used 3T structural MRI and probabilistic tractography to quantify the connectivity between the relevant brain areas. The results showed that participants who flexibly change response thresholds (as quantified by the mathematical model) have strong structural connections between presupplementary motor area and striatum. This result was confirmed in an independent second experiment. In general, these findings show that individual differences in elementary cognitive tasks are partly driven by structural differences in brain connectivity. Specifically, these findings support a cortico-striatal control account of how the brain implements adaptive switches between cautious and risky behavior.
当人们做出决策时，他们经常面临着对响应速度和响应准确性的相反要求，这个过程可能由响应阈值来介导。根据纹状体假说，人们通过增加皮质到纹状体的激活来降低响应阈值，从而使大脑摆脱抑制。根据 STN 假说，人们通过降低皮质到丘脑底核（STN）的激活来降低响应阈值；STN 活动的减少同样被认为可以使大脑摆脱抑制，从而导致快速但易错的反应。为了检验这些假说——这些假说可能都是正确的——我们在知觉决策中进行了两项实验，在这些实验中，我们使用线索来改变对速度与准确性的要求。在这两项实验中，行为数据和数学模型分析都证实了线索的指令选择性地影响了响应阈值的设置。在第一项实验中，我们使用超高分辨率 7T 结构 MRI 精确定位 STN。然后，我们使用 3T 结构 MRI 和概率性轨迹追踪来量化相关脑区之间的连通性。结果表明，那些能够灵活改变响应阈值的参与者（如数学模型所量化的），其预备运动区和纹状体之间存在强大的结构连接。在一个独立的第二项实验中，这一结果得到了证实。总的来说，这些发现表明，基本认知任务中的个体差异部分是由大脑连接结构差异驱动的。具体来说，这些发现支持了一种皮质-纹状体控制理论，即大脑如何在谨慎和冒险行为之间实现自适应切换。
