Sensory cortical organization and cross-modal plasticity in blind subjects

描述（由申请人提供）：视觉剥夺是导致大脑区域响应环境限制而采用新功能的最极端条件之一，即补偿感觉形态的丧失。对视力丧失的动物和盲人的研究早就证明了视觉皮层在处理非视觉信息时的跨模态招募。然而，人们对重组后的枕叶皮层的功能划分及其在非视觉信息处理和高级认知功能中的确切作用知之甚少。本项目的主要目的是(1)确定盲人受试者枕皮质的感觉组织，(2)确定盲人枕皮质的非视觉输入来源，以及(3)确定盲人受试者枕皮质在处理非视觉刺激时的功能作用，特别是在使用感觉替代装置时。使用功能性磁共振成像（fMRI），我们将检查与触觉和听觉刺激相关的大脑活动，同时受试者试图识别或定位刺激。这将使我们能够确定区域特异性是否存在于重组后的枕叶皮层中，用于感觉模式和/或识别和定位。利用弥散张量成像（Diffusion Tensor Imaging， DTI）和基于体素的形态测量（Voxel-Based Morphometry， VBM）这两种相对较新的结构MRI技术，研究盲人大脑适应性变化的结构基础。VBM将允许我们检查盲人枕皮质灰质细胞密度和体积是否与正常人枕皮质灰质细胞密度和体积相同；DTI将检查两组受试者的枕骨皮层和枕骨皮层白质纤维束的强度，从而确定盲人非视觉输入来源的相对变化。为了测试失明在多大程度上伴随着非视觉能力的增强，并确定枕皮质在盲人中的功能作用，我们将用扩展的心理物理评估来补充脑成像。我们将研究行为表现与触觉或听觉刺激激活大脑区域的协方差，特别是通过视觉-听觉感觉替代装置引起的知觉引起的枕叶激活。我们预测，根据感知到的刺激和/或执行的任务，并与使用熟练程度相称，在使用感觉替代装置期间，通常不被声音招募的大脑区域可以被激活。更好地了解失明中潜在的大脑和认知可塑性的生理机制将有助于为盲人制定更适当的康复策略和辅助装置，如视觉假体或感觉替代装置。从更广泛的角度来看，这将为我们提供关于大脑可塑性的有价值的信息，以及大脑如何根据环境约束修改自己的组织。这将进一步激发脑损伤患者神经心理学和康复方法的发展。

DESCRIPTION (provided by applicant): Visual deprivation is one of the most extreme conditions leading brain regions to adopt new functions in response to environmental constraints, that is, to compensate for the loss of a sensory modality. Studies in visually deprived animals and in blind humans have long demonstrated the cross-modal recruitment of the visual cortex to process non-visual information. Yet, little is known about the functional parcellation of the reorganized occipital cortex and its precise role in the processing of non-visual information and in higher cognitive functions. The main aims of the present project are (1) to determine the sensory organization of the occipital cortex in blind subjects, (2) to identify the source of non-visual input to occipital cortex in the blind, and (3) to determine the functional role of the occipital cortex of blind subjects in the processing of non-visual stimuli, particularly when using a sensory substitution device. Using functional Magnetic Resonance Imaging (fMRI), we will examine brain activity related to tactile and auditory stimulation while subjects try to either identify or localize stimuli. This will allow us to determine whether domain specificity exists within the reorganized occipital cortex for sensory modality and/or for identification and localization. Using Diffusion Tensor Imaging (DTI) and Voxel-Based Morphometry (VBM), two relatively novel structural MRI techniques, we will investigate the structural basis of cerebral adaptive changes in blind subjects. VBM will allow us to examine if grey-matter cell density and volume in the blind occipital cortex are the same as those in the occipital cortex of sighted persons; DTI will examine the strength of white-matter fiber tracts projecting to and from occipital cortex in both subject groups, thus determining relative changes in the source of non-visual input in the blind. To test to what extent blindness is accompanied by enhanced non-visual abilities and to determine the functional role of occipital cortex in the blind, we will supplement brain imaging with extended psychophysical evaluations. We will examine the co-variance of behavioral performance with activation of brain regions by tactile or auditory stimulation, and in particular with occipital activation elicited by perception through a visual- to-auditory sensory substitution device. We predict that brain areas that are normally not recruited by sounds can be activated during the use of the sensory substitution device according to the stimuli perceived and/or the task performed and commensurate with proficiency of use. PUBLIC HEALTH RELEVANCE A better understanding of the physiological mechanisms underlying brain and cognitive plasticity in blindness will help to develop more adequate rehabilitation strategies and assistive devices for the blind, such as visual prostheses or sensory substitution devices. In a wider perspective, this will provide us with valuable information regarding brain plasticity in general and how the brain modifies its own organization in response to environmental constraints. This could further inspire the development of neuropsychological and rehabilitation methods for patients with brain injuries.