知识引导的客体识别神经机制：功能磁共振研究

项目名称： 知识引导的客体识别神经机制：功能磁共振研究

项目编号： No.30800295

项目类型： 青年科学基金项目

立项/批准年度： 2009

项目学科： 无线电电子学、电信技术

项目作者： 甄宗雷

作者单位： 北京师范大学

项目金额： 18万元

中文摘要： 以fMRI为手段，本项目对top-down信息在客体识别中的神经机制进行了研究。以面孔这类客体作为切入点，研究首先在全脑定位出了多个对面孔敏感的脑区，其中既有位于枕、颞叶主要受bottom-up刺激驱动的脑区，又有位于顶、额叶，易受top-down信息影响的脑区。功能连接分析表明这些脑区构成三个子网络：面孔识别网络，语义网络和表达网络。进而，采用知觉学习范式调制被试在客体识别中的top-down信息，对top-down信息引导的客体识别神经机制进行了研究。结果表明：1) top-down信息会有选择的调制任务相关脑区：对形状判别任务进行学习，只会影响客体形状识别脑区激活强度，而对客体和英文单词的联合学习，则只会影响字形加工脑区的激活强度；2) top-down信息是通过影响客体识别脑功能网络完成的：面孔身份识别的学习会改变多个面孔敏感区对已学面孔的表征模式。3）对已学习客体，top-down信息可以很好的弥补任务和噪声带来的差异而对其进行识别：随top-down信息增多，面孔识别脑区对面孔身份匹配任务和运动方向匹配任务的脑激活模式越来越相似，对不同噪声面孔的激活模式，也越发相似。

中文关键词： 客体识别；功能磁共振；top-down信息；激活模式；知觉学习

英文摘要： The project aims to study how the top-down information influences object recognition and what is its neural mechanism. As a starting point, the role of top-down information in face perception was investigated. Twenty-five face selective regions were identified including both the bottom-up regions located in occipital and temporal cortex and top-down regions located in frontal cortex. Further, based on the functional connectivity between regions, we found that these regions are clustered into three relatively independent sub-networks: recognition network, expression network and semantic network, respectively. Then, we adopted perceptual learning paradigm to change the top-down information in object/face perception and observed how the top-down information would modulated the brain activity along the learning. In summary, there were three main findings. Firstly, the effects of top-down information depend on the task context in which that information is learned. Specifically, learning of novel visual stimuli produces a greater effect on the VWFA when those stimuli are associated with meanings (via association learning) but produces a greater effect on shape-processing regions when learning in a discrimination task without associated meanings. Second, the top-down information plays its role by modulating the most task-relevant cortical regions. Along the face identity learning, the neural patterns of most face selective regions (both bottom-up regions and top-down regions) were changed. Thirdly, top-down information can efficiently improve the signal-to-noise ratio of stimulus. Along the face identity learning, in most of face selective regions, the similarity between the neural representation for face embedded with much noise and the neural representation for face embedded with less noise increase gradually.

英文关键词： ：object recognition; functional MRI; top-down information; activity pattern; perceptual learning