健康与遗传心理学研究室知识库

在嗅觉信息加工领域，分析性的编码和整合性的编码是两大具有争议的主流观点。在人类嗅觉感知上，更多研究认为以经验驱动的整合性的气味编码占据主导作用。本研究从气味单质的编码和气味混合物的编码两个层面在人类身上发现分析性编码的存在，并且显著影响嗅觉感知。

研究一通过气味适应，在功能上降低被试对气味分子部分化学特征的敏感性，再结合心理物理测量方法和功能性核磁共振成像以及多体素的模式分析技术，发现对部分化学特征的适应改变了被试对整个气味的感知。神经证据显示，对部分化学特征的适应不仅降低了气味的激活强度，还改变了前梨状皮层和嗅觉眶额叶皮层对气味的编码。

研究二设计了一种更敏感的范式测量人类被试从气味混合物中提取气味单质的能力，结果发现人类可以从7个成分的气味混合物中提取出气味单质的信息，这高于前人研究所认为的3-4个成分的限制;与此同时，研究二引入了气味混合物的复杂度的概念，用心理物理法测量被试对气味混合物的相对复杂度的感知，结果发现气味混合物的成分数可以显著预测被试对气味混合物相对复杂度的感知，这种效应并不来自于成分增多而带来的强度和愉悦度的变化。

总体来说，本文分别从嗅觉单质和嗅觉混合物两个层面验证了人类嗅觉感知中分析性编码的成分。这种自下而上的信息加工成分长久以来在人类的嗅觉信息加工中被忽视，本研究的发现拓展了对人类嗅觉信息加工的认识。

Analytical processing or holistic processing are two main perspectives regarding the mechanisms of olfactory perception. In human, olfaction perception is generally viewed as configural process strongly driven by experience. Here two studies were conducted and proved that analytical process is indispensable to the representation of odor quality in both odor compound and odor mixture.

Study 1 functionally manipulated participants' sensitivity to partial chemical feature of an odor compound through adaptation followed by the psychophysical measurement and functional magnetic resonance imaging combing with multivariate pattern analysis. The results showed that adapting to partial chemical feature changed the perceived quality as well as neural ensembles of odors in anterior piriform cortex and olfactory orbitofrontal cortex. Cross adaptation between odor compounds sharing the same chemical feature were also observed in olfactory cortex.

Study 2 employed a sensitive measure and showed that participants were capable of extracting components in odor mixture consisting of 7 compounds, which preceded the long documented 3-4 compounds limitation. Moreover, we introduced the concept of mixture complexity and the corresponding psychophysical measurement and found that the perceived complexity can be predicted by the number of components in the mixture but not perceived intensity and pleasantness of the mixture.

In summary, we revealed analytical processing in human olfactory perception in terms of olfactory compound as well as olfactory mixture. This finding broadens our understanding to human olfaction perception that often underestimates bottom-up component.