Wellcome Trust Centre for Neuroimaging, University College London, London WC1N 3BG, United Kingdom.
J Neurosci. 2013 Apr 3;33(14):6160-9. doi: 10.1523/JNEUROSCI.4777-12.2013.
Neural representations of the effort deployed in performing actions, and the valence of the outcomes they yield, form the foundation of action choice. To discover whether brain areas represent effort and outcome valence together or if they represent one but not the other, we examined these variables in an explicitly orthogonal way. We did this by asking human subjects to exert one of two levels of effort to improve their chances of either winning or avoiding the loss of money. Subjects responded faster both when exerting greater effort and when exerting effort in anticipation of winning money. Using fMRI, we inspected BOLD responses during anticipation (before any action was executed) and when the outcome was delivered. In this way, we indexed BOLD signals associated with an anticipated need to exert effort and its affective consequences, as well as the effect of executed effort on the representation of outcomes. Anterior cingulate cortex and dorsal striatum (dorsal putamen) signaled the anticipation of effort independently of the prospect of winning or losing. Activity in ventral striatum (ventral putamen) was greater for better-than-expected outcomes compared with worse-than-expected outcomes, an effect attenuated in the context of having exerted greater effort. Our findings provide evidence that neural representations of anticipated actions are sensitive to the expected demands, but not to the expected value of their consequence, whereas representations of outcome value are discounted by exertion, commensurate with an integration of cost and benefit so as to approximate net value.
人类在执行动作时所付出的努力以及动作结果的效价,共同构成了动作选择的基础。为了发现大脑区域是否同时表示努力和结果效价,或者只表示其中之一,我们以一种明确的正交方式来研究这些变量。我们让人类受试者付出两种努力水平中的一种,以提高他们赢得或避免金钱损失的机会。当受试者付出更大的努力或预期赢得金钱时,他们的反应速度都会更快。使用 fMRI,我们在预期(在执行任何动作之前)和结果交付时检查了 BOLD 反应。通过这种方式,我们索引了与预期需要付出努力及其情感后果以及执行努力对结果表示的影响相关的 BOLD 信号。前扣带皮层和背侧纹状体(背侧苍白球)独立于输赢的前景,对努力的预期发出信号。与预期的结果相比,腹侧纹状体(腹侧苍白球)对超出预期的结果的活动更大,而在付出更大努力的情况下,这种效果会减弱。我们的研究结果表明,预期动作的神经表示对预期的要求敏感,但对其后果的预期价值不敏感,而结果价值的表示则因努力而被削弱,这与成本和收益的整合是一致的,以近似于净价值。