UCLA Psychology Department, University of California, Los Angeles, CA 90095-1563, USA.
J Cogn Neurosci. 2010 Sep;22(9):1970-9. doi: 10.1162/jocn.2009.21317.
Goal pursuit in humans sometimes involves approaching unpleasant and avoiding pleasant stimuli, such as when a dieter chooses to eat vegetables (although he does not like them) instead of doughnuts (which he greatly prefers). Previous neuroscience investigations have established a left-right prefrontal asymmetry between approaching pleasant and avoiding unpleasant stimuli, but these investigations typically do not untangle the roles of action motivation (approach vs. avoidance) and stimulus valence (pleasant vs. unpleasant) in this asymmetry. Additionally, studies on asymmetry have been conducted almost exclusively using electroencephalography and have been difficult to replicate using functional magnetic resonance imaging (fMRI). The present fMRI study uses a novel goal pursuit task that separates action motivation from stimulus valence and a region-of-interest analysis approach to address these limitations. Results suggest that prefrontal asymmetry is associated with action motivation and not with stimulus valence. Specifically, there was increased left (vs. right) activation in dorsolateral prefrontal cortex during approach (vs. avoidance) actions regardless of the stimulus valence, but no such effect was observed for pleasant compared to unpleasant stimuli. This asymmetry effect during approach-avoidance action motivations occurred in the dorsolateral but not orbito-frontal aspects of prefrontal cortex. Also, individual differences in approach-avoidance motivation moderated the effect such that increasing trait approach motivation was associated with greater left-sided asymmetry during approach actions (regardless of the stimulus valence). Together, these results support the notion that prefrontal asymmetry is associated with action motivation regardless of stimulus valence and, as such, might be linked with goal pursuit processes more broadly.
人类在追求目标时，有时需要接近不愉快的刺激，同时避免愉快的刺激，例如当节食者选择吃蔬菜（尽管他不喜欢吃）而不是甜甜圈（他非常喜欢吃）时。先前的神经科学研究已经确定了在接近愉快刺激和避免不愉快刺激之间存在左右前额叶不对称，但这些研究通常无法理清行动动机（接近与回避）和刺激效价（愉快与不愉快）在这种不对称中的作用。此外，关于不对称性的研究几乎都是使用脑电图进行的，并且使用功能磁共振成像（fMRI）进行的研究难以复制。本 fMRI 研究使用了一种新颖的目标追求任务，该任务将行动动机与刺激效价分开，并采用感兴趣区域分析方法来解决这些局限性。结果表明，前额叶不对称性与行动动机有关，而与刺激效价无关。具体来说，在进行接近（相对于回避）动作时，背外侧前额叶皮层的左侧（相对于右侧）激活增加，而与刺激效价无关，但对于愉快的刺激与不愉快的刺激相比，没有观察到这种效果。这种在接近-回避行动动机中的不对称效应发生在背外侧前额叶皮层，而不是眶额前皮层。此外，接近-回避动机的个体差异调节了这种效应，即增加特质接近动机与在接近动作时的左侧对称性增加有关（无论刺激效价如何）。总之，这些结果支持了这样一种观点，即前额叶不对称性与行动动机有关，而与刺激效价无关，因此可能与更广泛的目标追求过程有关。
