Sensory Cortical Organization and Cross-Modal Plasticity in Blind Humans

描述（由申请人提供）：众所周知，视觉剥夺和失明会导致某些大脑区域根据环境限制进行重组，以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，对于重组视觉皮层（VC）的功能专门化，它在非视觉信息处理中的确切作用，或者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层的功能组织，(2)检查非视觉信息在盲人的VC中是否分层处理，(3)确定适应性变化的结构基础和盲人VC的非视觉输入来源。该基金资助的三年研究结果表明，听觉和触觉加工确实存在空间和非空间加工流（Renier et al., 2009）。此外，早期失明的VC的空间听觉和触觉加工与正常受试者的视觉空间加工发生在相同的背流区域（Renier et al., 2010）。这些发现使我们假设，在早期失明的大脑皮层中保留了功能特殊的模块。我们将通过测试腹侧流中的范式来进一步研究这一假设。因此，使用功能性磁共振成像，我们将检查盲人受试者的大脑活动，同时他们识别（通过听觉模态）房屋，面孔和编码成声音模式的二维几何形状。这些实验将使我们能够确定海马旁位区（PPA）、梭状面区（FFA）和枕侧复合体（LOC）在早期失明中是否保留了它们指定的功能角色，同时改变了它们的输入方式。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，就像在其完整的感觉系统中处理正常感觉信息一样。利用复杂变化的音高信息，我们将确定盲人的早期到晚期视觉区域是否在简单到复杂的音高处理方向上对声音做出反应。最后，利用弥散张量成像（diffusion tensor imaging， DTI）和功能连通性分析，探讨盲人受试者大脑皮层和白质适应性变化的结构基础。使用DTI，我们将检查两个受试者组中投射到和来自VC的白质纤维束的强度，从而确定VC与其他皮质区域之间连接的相对变化。我们还将测试盲人和视力正常的志愿者在听觉和触觉信息处理过程中，视觉和其他感觉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通路的强度。结合这两种不同的方法将为我们提供一个极好的机会来识别早期盲期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.