同向性偏盲脑重组改变与盲视形成的发生机制研究

The homonymous hemianopsia (HH) is the most common cortical blindness representing 10% of stroke cases, which reduces significantly their quality of life. Blindsight, commonly associated with HH, is very important for significantly improving visual function and their quality of life since patients with blindsight gain better outcome than those without blindsight after visual stimuli rehabilitation training of HH. In addition, blindsight can become a unique experimental model for integrating the role of subcortical structures within the functional architecture of vision originally charted on the cortex. However, mechanisms of blindsight remain unclear. We conceive of blindsight as a constellation of multiple nonconscious visual abilities that likely reflect the variety of existing V1-independent subcortical pathways. We also hypothesize that the combination of three subcortical pathways is responsible for blindsight including lateral geniculate nucleus to extrastriate pathway, colliculo-pulvinar-extrastriate pathway, and colliculo-pulvinar-V4 pathway. Correlated with a multi-modal parcellation of human cerebral cortex and task related fMRI activation regions, visual cortical areas and some important subcortical structures are defined more accurately, which can make subcortical pathways and connecting fibers related to blindsight clear with high definition diffusion tensor tractography and voxel-mirrored homotopic connectivity methods. The results will provide objective evidences for understanding mechanisms of blindsight, improving rehabilitation outcome, and investigating the structures and function of visual related brain.

同向性偏盲是最常见皮质盲，约占卒中病例10%，明显降低了生活质量。同向性偏盲常伴盲视，其康复训练效果明显优于不伴盲视患者，因此，盲视形成对于提高视功能和生活质量非常重要。此外，盲视是研究视觉皮层下通路的最佳模型，对研究视觉相关脑区解剖和功能具有重要意义。然而，盲视发生机制不清，盲视是否有多条皮层下通路及二者之间的关系目前尚无定论。本项目提出“盲视患者存在与视觉通路背侧束和腹侧束连接的多条皮层下通路，其共同发挥作用是盲视的发生机制”的假说，拟通过人脑连接组计划脑图谱及视觉刺激和视觉运动刺激fMRI结果对感兴趣区准确定位勾画，采用fMRI导引的高清扩散张量纤维束成像方法以及运用镜像同伦方法对静息功能数据处理分析，并与心理物理学行为结果对照研究，回答盲视有哪几条皮层下通路以及二者之间关系的问题，从而验证假设并揭示盲视的发生机制，为提高视功能康复效果以及进一步阐明视觉相关脑区解剖和功能提供客观依据

同向性偏盲是最常见的皮质盲，其中伴盲视患者视觉康复训练后其视功能改善优于不伴盲视患者，因此，盲视形成对患者视功能提高至关重要。致盲性眼病可导致视功能不可逆性损伤，因此弄清同向性偏盲伴盲视与不伴盲视，以及致盲性眼病脑改变差异及机制有助于探索盲视形成的发生机制。本项目纳入同向性偏盲患者（包括伴盲视与不伴盲视患者），同时纳入致盲性眼病3类（青光眼、视神经脊髓炎谱系疾病相关性视神经炎、先天性单眼盲）患者和健康人作为对照，采用多模态脑功能成像研究患者脑微细结构、功能、灌注等改变、脑激活改变及其与临床指标的关系。研究发现：同向性偏盲伴盲视患者视觉区、视觉外脑区及皮层下核团、皮层下通路的微结构和功能发生重组。致盲性眼病患者脑改变包括：青光眼患者存在视觉通路内、外广泛的白质微结构的损伤，而且患者从初级视觉皮层到高级皮层的信息流减少，自上而下的处理增强；其白质损伤及信息流改变与视皮质的微结构损伤有关；为青光眼脑微结构损伤及脑功能重组提供理论依据；青光眼患者神经血管单元复合体的损伤不仅累及视觉皮层，还累及多个高级认知功能区；视觉区的损伤与视野缺损显著相关。视神经脊髓炎谱系疾病相关性视神经炎患者视觉皮层及认知系统微结构发生损伤，视觉皮层微结构损伤与视功能障碍有关。正眼压型青光眼患者皮层灰质微结构改变广泛，包括视觉皮层、突显网络相关皮层、默认网络相关皮层、背侧注意网络相关皮层、颞顶枕连接区、初级听皮层及眶回及额极的多发微结构损伤，脑微结构损伤与患者疾病严重程度相关。先天性单眼盲患者脑白质微结构发生广泛异常改变，从感觉模式到其他跨模态通路，包括语言、执行、记忆、情绪、精细运动和半球间交流。该研究阐明了同向性偏盲伴盲视患者视觉内、外多条通路结构、功能发生重组，其共同作用是盲视发生的重要机制。