Jin Jingwen, Zelano Christina, Gottfried Jay A, Mohanty Aprajita
Stony Brook University, Department of Psychology, Stony Brook, New York 11794-2500, and.
Northwestern University Feinberg School of Medicine, Department of Neurology, Chicago, Illinois 60611.
J Neurosci. 2015 Nov 11;35(45):15145-56. doi: 10.1523/JNEUROSCI.2450-15.2015.
Although the amygdala is a major locus for hedonic processing, how it encodes valence information is poorly understood. Given the hedonic potency of odor stimuli and the amygdala's anatomical proximity to the peripheral olfactory system, we combined high-resolution fMRI with pattern-based multivariate techniques to examine how valence information is encoded in the amygdala. Ten human subjects underwent fMRI scanning while smelling 9 odorants that systematically varied in perceived valence. Representational similarity analyses showed that amygdala codes the entire dimension of valence, ranging from pleasantness to unpleasantness. This unidimensional representation significantly correlated with self-reported valence ratings but not with intensity ratings. Furthermore, within-trial valence representations evolved over time, prioritizing earlier differentiation of unpleasant stimuli. Together, these findings underscore the idea that both spatial and temporal features uniquely encode pleasant and unpleasant odor valence in the amygdala. The availability of a unidimensional valence code in the amygdala, distributed in both space and time, would create greater flexibility in determining the pleasantness or unpleasantness of stimuli, providing a mechanism by which expectation, context, attention, and learning could influence affective boundaries for guiding behavior.
Our findings elucidate the mechanisms of affective processing in the amygdala by demonstrating that this brain region represents the entire valence dimension from pleasant to unpleasant. An important implication of this unidimensional valence code is that pleasant and unpleasant valence cannot coexist in the amygdale because overlap of fMRI ensemble patterns for these two valence extremes obscures their unique content. This functional architecture, whereby subjective valence maps onto a pattern continuum between pleasant and unpleasant poles, offers a robust mechanism by which context, expectation, and experience could alter the set-point for valence-based behavior. Finally, identification of spatial and temporal differentiation of valence in amygdala may shed new insights into individual differences in emotional responding, with potential relevance for affective disorders.
尽管杏仁核是享乐加工的主要位点，但人们对其如何编码效价信息知之甚少。鉴于气味刺激的享乐效力以及杏仁核在解剖学上与外周嗅觉系统的接近程度，我们将高分辨率功能磁共振成像（fMRI）与基于模式的多变量技术相结合，以研究效价信息在杏仁核中是如何编码的。10名人类受试者在闻9种在感知效价上有系统变化的气味剂时接受了fMRI扫描。表征相似性分析表明，杏仁核编码了从愉悦到不愉悦的整个效价维度。这种单维表征与自我报告的效价评分显著相关，但与强度评分无关。此外，试验内的效价表征随时间演变，优先对不愉快刺激进行早期区分。总之，这些发现强调了空间和时间特征在杏仁核中独特地编码愉悦和不愉悦气味效价的观点。杏仁核中存在一种在空间和时间上分布的单维效价编码，这将在确定刺激的愉悦性或不愉悦性方面创造更大的灵活性，提供一种机制，通过该机制期望、情境、注意力和学习可以影响情感边界以指导行为。
我们的研究结果通过证明该脑区代表从愉悦到不愉悦的整个效价维度，阐明了杏仁核中情感加工的机制。这种单维效价编码的一个重要含义是，愉悦和不愉悦的效价不能在杏仁核中共存，因为这两个极端效价的fMRI总体模式重叠会掩盖它们的独特内容。这种功能结构，即主观效价映射到愉悦和不愉悦两极之间的模式连续体上，提供了一种强大的机制，通过该机制情境、期望和经验可以改变基于效价行为的设定点。最后，识别杏仁核中效价的空间和时间差异可能为情绪反应的个体差异提供新的见解，这对情感障碍可能具有潜在相关性。
