Wellcome Trust Centre for Neuroimaging, Institute of Neurology, University College London, London WC1N 3BG, United Kingdom.
J Neurosci. 2012 May 16;32(20):7009-20. doi: 10.1523/JNEUROSCI.0049-12.2012.
Value-based choices are influenced both by risk in potential outcomes and by whether outcomes reflect potential gains or losses. These variables are held to be related in a specific fashion, manifest in risk aversion for gains and risk seeking for losses. Instead, we hypothesized that there are independent impacts of risk and loss on choice such that, depending on context, subjects can show either risk aversion for gains and risk seeking for losses or the exact opposite. We demonstrate this independence in a gambling task, by selectively reversing a loss-induced effect (causing more gambling for gains than losses and the reverse) while leaving risk aversion unaffected. Consistent with these dissociable behavioral impacts of risk and loss, fMRI data revealed dissociable neural correlates of these variables, with parietal cortex tracking risk and orbitofrontal cortex and striatum tracking loss. Based on our neural data, we hypothesized that risk and loss influence action selection through approach-avoidance mechanisms, a hypothesis supported in an experiment in which we show valence and risk-dependent reaction time effects in line with this putative mechanism. We suggest that in the choice process risk and loss can independently engage approach-avoidance mechanisms. This can provide a novel explanation for how risk influences action selection and explains both classically described choice behavior as well as behavioral patterns not predicted by existing theory.
基于价值的选择既受到潜在结果风险的影响，也受到结果是否反映潜在收益或损失的影响。这些变量被认为以特定的方式相关，表现为对收益的风险规避和对损失的风险寻求。相反，我们假设风险和损失对选择有独立的影响，以至于根据具体情况，受试者可以表现出对收益的风险规避和对损失的风险寻求，或者正好相反。我们在一项赌博任务中证明了这种独立性，通过选择性地反转损失引起的效应（导致对收益的赌博多于损失，反之亦然），而不影响风险规避。与风险和损失的这些可分离的行为影响一致，fMRI 数据显示了这些变量的可分离的神经相关性，顶叶皮层跟踪风险，眶额皮层和纹状体跟踪损失。基于我们的神经数据，我们假设风险和损失通过趋近-回避机制影响行为选择，这一假设在一项实验中得到了支持，该实验显示了与这种推测机制一致的效价和风险依赖的反应时间效应。我们认为，在选择过程中，风险和损失可以独立地参与趋近-回避机制。这可以为风险如何影响行为选择提供一个新的解释，并且解释了既有理论无法预测的经典描述的选择行为以及行为模式。
