Kim M Justin, Mattek Alison M, Bennett Randi H, Solomon Kimberly M, Shin Jin, Whalen Paul J
Department of Psychological and Brain Sciences, Dartmouth College, Hanover, New Hampshire 03755,
Department of Psychology and Neuroscience, Duke University, Durham, North Carolina 27708, and.
J Neurosci. 2017 Sep 27;37(39):9510-9518. doi: 10.1523/JNEUROSCI.1375-17.2017. Epub 2017 Sep 5.
Human amygdala function has been traditionally associated with processing the affective valence (negative vs positive) of an emotionally charged event, especially those that signal fear or threat. However, this account of human amygdala function can be explained by alternative views, which posit that the amygdala might be tuned to either (1) general emotional arousal (activation vs deactivation) or (2) specific emotion categories (fear vs happy). Delineating the pure effects of valence independent of arousal or emotion category is a challenging task, given that these variables naturally covary under many circumstances. To circumvent this issue and test the sensitivity of the human amygdala to valence values specifically, we measured the dimension of valence within the single facial expression category of surprise. Given the inherent valence ambiguity of this category, we show that surprised expression exemplars are attributed valence and arousal values that are uniquely and naturally uncorrelated. We then present fMRI data from both sexes, showing that the amygdala tracks these consensus valence values. Finally, we provide evidence that these valence values are linked to specific visual features of the mouth region, isolating the signal by which the amygdala detects this valence information. There is an open question as to whether human amygdala function tracks the valence value of cues in the environment, as opposed to either a more general emotional arousal value or a more specific emotion category distinction. Here, we demonstrate the utility of surprised facial expressions because exemplars within this emotion category take on valence values spanning the dimension of bipolar valence (positive to negative) at a consistent level of emotional arousal. Functional neuroimaging data showed that amygdala responses tracked the valence of surprised facial expressions, unconfounded by arousal. Furthermore, a machine learning classifier identified particular visual features of the mouth region that predicted this valence effect, isolating the specific visual signal that might be driving this neural valence response.
传统上，人类杏仁核的功能与处理情绪激动事件的情感效价（消极与积极）相关，尤其是那些发出恐惧或威胁信号的事件。然而，关于人类杏仁核功能的这种解释可以由其他观点来解释，这些观点认为杏仁核可能被调整为对以下两者之一做出反应：（1）一般情绪唤醒（激活与去激活）或（2）特定情绪类别（恐惧与快乐）。鉴于这些变量在许多情况下自然地相互关联，描绘独立于唤醒或情绪类别的效价的纯粹影响是一项具有挑战性的任务。为了规避这个问题并专门测试人类杏仁核对效价值的敏感性，我们在单一的惊讶面部表情类别中测量了效价维度。鉴于该类别的内在效价模糊性，我们表明惊讶表情样本被赋予的效价和唤醒值是独特且自然不相关的。然后，我们展示了来自两性的功能磁共振成像数据，表明杏仁核追踪这些一致的效价值。最后，我们提供证据表明这些效价值与嘴部区域的特定视觉特征相关联，从而分离出杏仁核检测此效价信息的信号。关于人类杏仁核功能是追踪环境中线索的效价值，还是更一般的情绪唤醒值或更特定的情绪类别区分，存在一个悬而未决的问题。在这里，我们证明了惊讶面部表情的效用，因为这个情绪类别中的样本在一致的情绪唤醒水平下呈现出跨越双极效价维度（从积极到消极）的效价值。功能性神经成像数据表明，杏仁核的反应追踪了惊讶面部表情的效价，不受唤醒的干扰。此外，一个机器学习分类器识别出了嘴部区域预测这种效价效应的特定视觉特征，分离出了可能驱动这种神经效价反应的特定视觉信号。
