Sensory Cortical Organization and Cross-Modal Plasticity in Blind Humans

描述（由申请人提供）：视觉剥夺和失明会导致某些大脑区域重新组织，以应对环境限制，并补偿感觉模态的损失。对视觉剥夺动物和盲人的研究早已证明了视觉皮层处理非视觉信息的跨通道招募。然而，很少有人知道重组的视觉皮层（VC）的功能专业化，其在处理非视觉信息的确切作用，或其非视觉输入的来源和路由。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）检查盲人VC中非视觉信息是否分层处理，（3）确定盲人VC适应性变化的结构基础和非视觉输入的来源。该基金资助三年的结果表明，听觉和触觉处理确实存在空间和非空间处理流（Renier等人，2009年）。此外，早期盲人VC中的空间听觉和触觉处理与视力正常的受试者中的视觉空间处理发生在相同的背流区域中（Renier等人，2010年）。这些发现使我们假设，功能专门模块保存在早期盲人的皮层中。我们将通过测试腹侧流中的范例来进一步追求这一假设。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，而他们识别（通过听觉模态）的房屋，面孔和二维几何形状编码成声音模式。这些实验将使我们能够确定海马旁位置区（PPA），梭状面区（FFA）和枕叶外侧复合体（ESTA）是否保留其指定的功能作用在早期失明，而切换其输入方式。我们还将通过测试非视觉信息是否以分层的方式处理来检查VC的组织，就像正常的感觉信息在其完整的感觉系统中处理一样。使用复杂度不同的音高信息，我们将确定是否早期到晚期的视觉区域的盲人响应声音的方向简单到复杂的音高处理水平。最后，利用扩散张量成像（DTI）和功能连接的分析，我们将调查的结构基础的适应性变化的大脑皮层和白色物质的盲人。使用DTI，我们将检查两个受试者组中投射到VC和从VC投射的白质纤维束的强度，从而确定VC和其他皮质区域之间连接的相对变化。我们还将测试视觉和其他感觉区域如何在盲人和视力正常的志愿者的听觉和触觉信息处理过程中相互作用，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很好的机会，以确定来源的非视觉输入VC在早期失明。

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.