人脑初级视觉皮层结构和功能的磁共振影像学研究

CASIA OpenIR > 毕业生 > 博士学位论文

	人脑初级视觉皮层结构和功能的磁共振影像学研究
	李俏俊1,2
	2016-05-26
学位类型	工学博士
中文摘要	视觉是人类获取外部信息最主要的手段。初级视觉皮层对于视觉信息处理有着至关重要的作用。传统观点认为初级视觉皮层是一个结构和功能单一的结构，然而这个观点最近正在被许多研究发现所挑战。本文基于多模态磁共振成像探索初级视觉皮层是否存在结构亚区，然后研究各亚区参与的功能。同时我们还探索了初级视觉皮层受视觉剥夺影响的关键期。本文的主要成果如下： 1. 提出基于局部连接信息对初级皮层进行分区的学术思想。基于弥散磁共振成像的结构连接模式被广泛用于大脑皮层的分区研究。目前基于结构连接信息进行分区的方法大部分是利用全局或者长程连接模式。基于初级皮层具有很高的局部连接纤维以及功能密度的特性，本文提出对初级皮层分区应该使用局部连接模式。我们基于全局、长程以及局部连接模式三种不同信息对四个初级皮层（初级视觉皮层、初级听觉皮层、初级运动皮层和初级感觉皮层）进行分区，结果表明结构连接模式分区得到的亚区与细胞构筑得到的亚区一致。更进一步，相较于其它两种模式，基于局部连接模式得到的结果具有更好的稳定性。这个结果提示对于大脑皮层分区应该充分考虑大脑皮层的特性而选取相应的研究策略。 2. 发现初级视觉皮层亚区存在结构和功能上的分离与整合。现有的视觉通路理论认为初级视觉皮层同时参与背侧视觉通路和腹侧视觉通路，然而对它如何分别参与不同视觉通路的机制并不清楚。结合经典的视网膜拓扑定位图以及不断出现的关于初级视觉皮层结构和功能复杂性的研究成果，我们认为初级视觉皮层的亚区存在结构和功能上的分离和整合。我们基于静息态功能磁共振成像和弥散张量成像数据发现初级视觉皮层前侧亚区主要参与背侧视觉通路，后侧亚区主要参与腹侧视觉通路。与此同时，前后侧亚区存在显著的整合现象。该结果验证了我们的假设，拓展了现有的视觉通路理论。 3. 研究了失明年龄对于初级视觉皮层厚度发育的影响。初级视觉皮层会经历一个不断发育成熟的过程，而视觉剥夺会影响这个过程。研究发现相较于正常人，早期视觉剥夺盲人的初级视觉皮层会变厚，而在晚期视觉剥夺盲人中却没有这种变化。因而，我们认为视觉剥夺对于皮层厚度发育的影响存在关键期。本文基于曲线拟合的方法刻画盲人初级视觉皮层厚度随失明年龄变化的轨迹。结果表明初级视觉皮层厚度受视觉剥夺影响主要在儿童期以及青春后期之前这个阶段。这个发现对于我们进一步了解初级视觉皮层的发育机制具有重要借鉴意义。
英文摘要	Vision is the most important means of human to obtain external information. The primary visual cortex (V1) is the vital cortex for processing visual information. Traditionally, it is thought to be functionally and structurally homogeneous. However, this viewpoint is being challenged. In this study, based on multi-model magnetic resonance imaging (MRI), we explored the subregions of the V1 and their functions. Moreover, we explored the critical period of visual deprivation affecting the development of the V1. The main achievements of our study can be listed as follows: 1. We proposed that local connectivity profiles should be used for parcellating the primary cerebral cortex. Connectivity-based parcellation using diffusion tensor imaging (DTI) has been extensively used to parcellate subcortical areas and the association cortex. Connectivity profiles are vital for this method and two categories of connectivity profiles are generally utilized, the global connectivity profiles and long connectivity profiles. Because the primary cerebral cortices are rich in local anatomical connections and possess high degree of local functional density, we proposed that local structural connectivity profiles should be used for parcellating the primary cerebral cortices. In this study, the global, long, and local connectivity profiles were separately used to parcellate the bilateral M1, A1, S1, and V1. We found that results using the three profiles were all quite consistent with reported cytoarchitectonic evidences. More importantly, the results using local connectivity profiles showed less inter-subject variability than the results using the other two, a finding which suggested that local connectivity profiles were superior to global and long connectivity profiles for parcellating the primary cerebral cortices. This implies that, depending on the characteristics of specific areas of the cerebral cortex, different connectivity profiles may need to be adopted to parcellate different areas. 2. We observed the structural and functional segregation and integration of the subregions of the V1. The V1 is thought to be involved in both the dorsal visual pathway and the ventral pathway. However, the underlying mechanism for it to participate in two pathway separately is still unclear. Considering the retinotopy of the V1 and the increasing evidences showing that the V1 were more complicated than ever thought in both structures and functions, we hypothesized that a mechanism of segregation and integration may exist in subregions of the V1. Exploring the resting-state functional MRI (rs-fMRI) and DTI, we found that the anterior subregion were more involved in the dorsal visual pathway, while the posterior subregion were more involved in the ventral pathway. And, structural and functional integration were observed between the two subregions. These findings validated our hypothesis and deepened our understanding of the existing two-pathway visual theory. 3. We explored the effect of the age of blindness onset on the cortical thickness development of the human V1. Visual deprivation will impair the development of the V1. The MRI studies demonstrated that the bilateral V1 of the early blind were significantly thicker than the normal controls, while no significant differences were observed between the late blind and the normal controls. This implies that the age of blindness onset may exert significant effects on the development of cortical thickness of the the V1. Here we explored this issue by mapping the cortical thickness trajectory of the V1 against the age of blindness onset. We found that the cortical thickness were mostly affected during childhood and adolescence, which suggested a critical period for cortical development of the human V1. These findings shed light on our understanding of the development of the V1.
关键词	多模态磁共振成像初级视觉皮层视觉通路视觉剥夺亚区皮层厚度发育
文献类型	学位论文
条目标识符	http://ir.ia.ac.cn/handle/173211/11489
专题	毕业生_博士学位论文
作者单位	1.中国科学院自动化研究所模式识别国家重点实验室 2.中国科学院自动化研究所脑网络组研究中心
第一作者单位	模式识别国家重点实验室; 脑网络组研究
推荐引用方式 GB/T 7714	李俏俊. 人脑初级视觉皮层结构和功能的磁共振影像学研究[D]. 北京. 中国科学院大学,2016.

条目包含的文件
文件名称/大小	文献类型	版本类型	开放类型	使用许可
李俏俊_博士论文最终版.pdf（74000KB）	学位论文		限制开放	CC BY-NC-SA