Sensory Cortical Organization and Cross-Modal Plasticity in Blind Humans

描述(申请人提供)：众所周知，视觉剥夺和失明会导致大脑的某些区域重组，以应对环境的限制，并弥补感觉通道的丧失。对视觉剥夺动物和盲人的研究早就证明了视觉皮质处理非视觉信息的跨模式招募。然而，关于重组视皮层的功能特化、它在非视觉信息处理中的确切作用、以及它的非视觉输入的来源和路径，人们知之甚少。因此，本项目的主要目的是(1)使用感觉替代装置确定盲人志愿者枕叶皮质的功能组织；(2)检查盲人VC中非视觉信息是否被分级处理；(3)确定盲人VC的适应性变化的结构基础和非视觉输入的来源。这笔赠款资助三年的结果表明，听觉和触觉加工确实存在空间和非空间加工流(Renier等人，2009年)。此外，早期盲人Vc的空间听觉和触觉加工与有视力受试者的视觉空间加工发生在相同的背流区(Renier等人，2010)。这些发现让我们假设，功能特化的模块保存在早期盲人的大脑皮层中。我们将通过测试腹侧流中的范例来进一步研究这一假说。因此，使用功能磁共振成像，我们将检查盲人受试者在识别(通过听觉模式)房屋、面孔和编码为声音模式的二维几何形状时的大脑活动。这些实验将使我们能够确定在早期失明时，海马旁区域(PPA)、梭状面区域(FFA)和枕侧复合体(LOC)是否保留了它们指定的功能，同时改变了它们的输入通道。我们还将通过测试非视觉信息是否以分层方式处理，来检查VC的组织结构，就像正常感觉信息在其完整的感觉系统中处理一样。使用复杂程度不同的音调信息，我们将确定盲人的早到晚视觉区域是否以从简单到复杂的音调处理水平的方向对声音做出反应。最后，利用弥散张量成像(DTI)和功能连通性分析，探讨失明受试者大脑皮层和白质适应性改变的结构基础。使用DTI，我们将检查两组受试者中投射到VC和从VC发出的白质纤维束的强度，从而确定VC和其他皮质区域之间联系的相对变化。我们还将测试盲人和有视力的志愿者在听觉和触觉信息处理过程中视觉和其他感官区域是如何相互作用的，以及这种相互作用是否取决于连接这些区域的解剖路径的强度。将这两种不同的方法结合起来，将为我们提供一个很好的机会来识别早期盲人VC的非视觉输入来源。

DESCRIPTION (provided by applicant): Visual deprivation and blindness famously cause certain brain regions to reorganize in response to environmental constraints and in order to compensate for the loss of a sensory modality. Studies in visually deprived animals and blind humans have long demonstrated the cross-modal recruitment of the visual cortex to process nonvisual information. Yet, little is known about the functional specialization of the reorganized visual cortex (VC), its precise role in the processing of nonvisual information, or the source and routing of its nonvisual inputs. The main aims of the present project are, therefore, to (1) determine the functional organization of the occipital cortex in blind volunteers using a sensory substitution device, (2) to examine whether nonvisual information is processed hierarchically in the VC of the blind, and (3) identify the structural basis of adaptive changes and the source of nonvisual input to VC in the blind. Results from three years of funding by this grant have demonstrated that spatial and nonspatial processing streams do indeed exist for auditory and tactile processing (Renier et al., 2009). Furthermore, spatial auditory and tactile processing in the VC of the early blind occur in the same dorsal-stream regions as visual spatial processing in sighted subjects (Renier et al., 2010). These findings have led us to hypothesize that functionally specialized modules are preserved in the cortex of the early blind. We will pursue this hypothesis further by testing paradigms within the ventral stream. Thus, using functional magnetic resonance imaging, we will examine brain activity in blind subjects while they identify (via the auditory modality) houses, faces and 2-D geometrical shapes coded into sound patterns. These experiments will allow us to determine whether the parahippocampal place area (PPA), the fusiform face area (FFA), and the lateral occipital complex (LOC) retain their designated functional roles in early blindness, while switching their input modality. We will also examine the organization of VC by testing whether nonvisual information is processed in a hierarchical manner, in the same way that normal sensory information is processed in its intact sensory system. Using complexity-varied pitch information, we will determine if early-to-late visual regions of the blind respond to sound in the direction of simple-to-complex levels of pitch processing. Finally, using diffusion tensor imaging (DTI) and analysis of functional connectivity, we will investigate the structural basis of adaptive changes in the cerebral cortex and white matter of blind subjects. Using DTI, we will examine the strength of white-matter fiber tracts projecting to and from VC in both subject groups, thus determining relative changes in the connections between VC and other cortical areas. We will also test how visual and other sensory areas interact during auditory and tactile information processing in blind and sighted volunteers, and whether this interaction depends on the strength of anatomical pathways connecting these areas. Combining the two different methodological approaches will provide us an excellent opportunity to identify the source of nonvisual inputs to VC in the early blind.