物体的整体知觉加工的皮层下通路的研究

The visual system needs to process rapidly and coarsely part of information in the environment, in order to obtain the most useful information for survival. which of the properties, the global or the local (e.g., orientation of lines), is prioritized in the visual processing? There is behavioral evidence supporting "global first" (GF), while the underlying neural mechanisms remain unknown. Some researchers attribute GF to the distinct difference of spatial frequence of the figures, i.e., global information embodied by low spatial frequency is processed through the transient magnocellular (M) pathway, which is consequently faster than local information by high spatial frequency through the sustained parvocellular (P) pathways. However, in our experiment, we found the effect of GF remained even when the factor of spatial frequency was balanced across visual stimuli. This finding suggests that GF may not be restricted to the factor of spatial frequency but involve distinct neural basis. We hypothesize that the global properties of objects may be processed fast through the subcortial M pathway, and exhibit further influence on the processing of local properties through the connections of M and P pathways. We plan to adopt TMS technology for interrupting cortical visual pathway, and high resolution 7T functional MRI. Moreover, it is reported that some brain disorders (e.g., schizophrenia and glaucoma) are related to the dysfunction of M pathways, which also impaired patients' global perception. Therefore, the current project studying the visual pathway for processing global information will help not only, in theoretical significance, understand the neural mechanisms of visual processing system, but also, in practical value, seek an objective diagnostic criteria for related disorders such as schizophrenia.

视觉系统在对周围信息进行精细加工前首先需要快速地获得对生存最有利的信息。是物体的整体信息还是局部特征信息（如朝向）被优先加工？目前很多行为证据支持"整体优先"，然而其神经机制尚不清楚。一些观点认为整体优先于局部可以归因于图形的空间频率的差异，即整体对应的低频信息在M通路的加工快于局部对应的高频信息在P通路的加工。然而申请者已完成的实验提示，在对照了空间频率因素后，整体知觉仍然优先于局部，这说明"整体优先"有其自身的神经机制。我们认为整体性质可能经由皮层下M通路得到快速加工，并且通过不同通路间的皮层联系来调制局部性质的加工。本项目拟采用TMS阻断皮层上通路，以及高分辨的7T脑功能成像等技术方法来研究。此外，已有研究表明精神分裂患者M通路受损，且整体知觉也可能受损。因此，本研究不仅对深入了解视觉系统的工作机理具有重要的理论意义，而且对于寻找精神分裂症的客观诊断标准也有重要的临床应用价值。

视觉系统在对周围信息进行精细加工前首先需要快速地获得对生存最有利的信息。是物体的整体信息还是局部特征信息（如朝向）被优先加工？目前很多行为证据支持“整体优先”，然而其神经机制尚不清楚。基于之前的实验结果我们提出整体性质经由皮层下通路快速加工的假设。我们采用多种视觉行为范式，一致地发现整体性质主要由快速大细胞通路加工，局部性质则主要由慢速小细胞通路加工。另外透颅磁刺激TMS以及功能磁共振fMRI的结果提示整体性质可能经由以上丘、丘脑枕和杏仁核为主要节点的皮层下通路得到快速加工。为整体性质经由皮层下通路加工的假设提供了人类被试的间接证据。进一步地，为了能获得直接的神经环路的证据，我们开展了以啮齿类为研究对象的整体性质加工的皮层下神经环路的工作，目前已获得初步数据支持“整体优先”现象也存在于小鼠上，且在皮层下通路的上丘存在对整体和局部性质有不同的c-fos激活水平的神经元。本研究为“整体优先”提供了神经环路证据，对于深入了解视觉系统的工作机理具有重要的理论意义，而且对于寻找自闭症、精神分裂症等脑疾病的客观诊断标准也有重要的临床应用价值。