Brain and Cognition, Department of Psychology, University of Amsterdam, 1018 XA, Amsterdam, The Netherlands.
Proc Natl Acad Sci U S A. 2014 Feb 4;111(5):E618-25. doi: 10.1073/pnas.1317557111. Epub 2014 Jan 21.
A number of studies have shown that pupil size increases transiently during effortful decisions. These decision-related changes in pupil size are mediated by central neuromodulatory systems, which also influence the internal state of brain regions engaged in decision making. It has been proposed that pupil-linked neuromodulatory systems are activated by the termination of decision processes, and, consequently, that these systems primarily affect the postdecisional brain state. Here, we present pupil results that run contrary to this proposal, suggesting an important intradecisional role. We measured pupil size while subjects formed protracted decisions about the presence or absence ("yes" vs. "no") of a visual contrast signal embedded in dynamic noise. Linear systems analysis revealed that the pupil was significantly driven by a sustained input throughout the course of the decision formation. This sustained component was larger than the transient component during the final choice (indicated by button press). The overall amplitude of pupil dilation during decision formation was bigger before yes than no choices, irrespective of the physical presence of the target signal. Remarkably, the magnitude of this pupil choice effect (yes > no) reflected the individual criterion: it was strongest in conservative subjects choosing yes against their bias. We conclude that the central neuromodulatory systems controlling pupil size are continuously engaged during decision formation in a way that reveals how the upcoming choice relates to the decision maker's attitude. Changes in brain state seem to interact with biased decision making in the face of uncertainty.
许多研究表明，在努力做出决策时，瞳孔大小会短暂增大。这些与决策相关的瞳孔大小变化是由中枢神经调质系统介导的，这些系统也会影响参与决策的大脑区域的内部状态。有人提出，与决策相关的神经调质系统是由决策过程的终止激活的，因此，这些系统主要影响决策后的大脑状态。在这里，我们提出了与这一观点相反的瞳孔结果，表明其在决策过程中起着重要作用。我们在受试者对动态噪声中嵌入的视觉对比信号的存在与否（“是”与“否”）做出长时间决策时测量了瞳孔大小。线性系统分析显示，在决策形成过程中，瞳孔受到持续输入的显著驱动。在最终选择（由按钮按下表示）期间，这个持续分量比瞬态分量大。在决策形成过程中，瞳孔扩张的总体幅度在“是”选择时比“否”选择时更大，无论目标信号的物理存在与否。值得注意的是，这种瞳孔选择效应（“是”>“否”）的大小反映了个体的决策标准：在选择“是”以对抗偏见的保守受试者中，这种效应最强。我们得出结论，控制瞳孔大小的中枢神经调质系统在决策形成过程中持续参与，揭示了即将到来的选择与决策者态度的关系。在面对不确定性时，大脑状态的变化似乎与有偏差的决策相互作用。
