ATTENTION IN AGING AND EARLY ALZHEIMER'S DEMENTIA

阿尔茨海默型痴呆(DAT)的诊断主要表现为 DAT早期认知改变对临床医学的挑战 很难与那些伴随着正常成人衰老的人区分开来。 然而，正电子发射断层扫描(PET)研究表明， 大脑代谢的地形图在早期阶段被改变 阿尔茨海默病(AD)。这些研究指向有选择性的， 尤其是阿尔茨海默病患者关联区的皮质断开 后顶叶、颞叶和额叶皮质。这些领域发挥着重要作用 在注意力功能的控制中起主要作用。因此， 受阿尔茨海默病影响的皮质通路也有很大影响 大脑皮层的注意系统。最近的研究表明， 注意力障碍可以在轻度痴呆的受试者中检测到，并可能 先于受AD影响的所有其他非记忆功能的缺陷。一个 提出了DAT注意的神经解剖学模型，假设 分离但相互作用的皮质环路相关的功能障碍 有不同形式的视觉选择性注意。涉及的电路 顶后、纹外和联合的颞区是 假定用于协调基于位置、基于要素和基于对象 分别是选择性注意。 对DAT患者、健康的、年龄匹配的对照组和 建议正常的年轻人和老年人。注意和衡量标准 所有研究都将提供静息的大脑新陈代谢；PET成像 将在一项研究中检查与注意力相关的脑血流的变化。 早期DAT中视觉选择性注意的两个主要方面是 已检查、基于位置和基于要素/对象的选择，使用 关于隐蔽视觉空间的成熟信息处理测验 注意和视觉搜索。这两项正常的、与年龄相关的变化 视觉选择性注意的方方面面也将被调查。 在老龄化和DAT中将研究基于位置的选择性注意 前三个实验，包括纵向研究检查 最初轻度DAT受试者在三年时间内的变化。最后 三个实验将检验基于特征和基于对象的选择 正常人注意及其与视觉空间注意的交互作用 衰老和DAT。注意力的神经解剖模型将通过以下方式进行评估 (I)使用已知依赖于功能的注意任务 模型中所代表的皮质区域的完整性；以及(Ii)使用PET 静息脑代谢和任务相关脑血液的成像 血流至指数功能障碍在假设的新皮质区域及其 轻度DAT与注意表现的关系。 这项拟议的研究意义重大，因为 DAT的早期阶段尚未得到广泛研究。早期研究 认知能力(注意力)和生理功能的变化 (大脑新陈代谢和血流)及其相互关系 对于开发可靠的DAT早期诊断标志物至关重要。这个 研究还将提高对注意力正常老化的理解。 这项研究的独特贡献是大脑代谢的变化 将检查与注意力变化相关的 正常老化和DAT。

Diagnosis of dementia of the Alzheimer type (DAT) presents a major challenge to clinical medicine because the early cognitive changes in DAT are difficult to distinguish from those accompanying normal adult aging. Positron emission tomography (PET) studies have shown, however, that the topography of cerebral metabolism is altered in the early stages at Alzheimer's disease (AD). These studies point to selective, corticocortical disconnections of association areas in AD, in particular the posterior parietal, temporal, and frontal cortices. These areas play a major role in the control of attentional functions. Thus, the corticocortical pathways affected by AD are also substantially involved with cortical systems of attention. Recent studies indicate that attentional impairment can be detected in mildly demented subjects and may precede deficits in all other nonmemory functions affected by AD. A neuroanatomical model of attention in DAT is proposed, postulating dysfunction of separate but interacting corticocortical circuits associated with different forms of visual selective attention. Circuits involving posterior parietal, extrastriate, and association temporal areas are postulated to mediate location-based, feature-based, and object-based selective attention, respectively. A series of six studies of DAT patients, healthy, age-matched controls, and normal young and older adults is proposed. Measures of attention and resting cerebral metabolism will be available in all studies; PET imaging of attention-related cerebral blood flow will be examined in one study. Two broad aspects of visual selective attention in early DAT will be examined, location-based and feature/object-based selection, using well-established information-processing tests of covert visuospatial attention and visual search. Normal, age-related changes in these two aspects of visual selective attention will also be investigated. Location-based selective attention in aging and DAT will be investigated in the first three experiments, including a longitudinal study examining changes over a three-year period in initially mild DAT subjects. The last three experiments will examine feature-based and object-based selective attention and their interactions with visuospatial attention in normal aging and DAT. The neuroanatomical model of attention will be evaluated by (i) using attention tasks that are known to depend upon the functional integrity of cortical areas represented in the model; and (ii) using PET imaging of both resting cerebral metabolism and task-related cerebral blood flow to index dysfunctions in the postulated neocortical areas and their relation to attentional performance in mild DAT. The proposed research is significant because changes in attention in the early stages of DAT have not been studied extensively. Studies of early changes in cognitive abilities (attention) and physiological functioning (cerebral metabolism and blood flow) and their interrelationships are essential for developing reliable markers for early diagnosis of DAT. The research will also improve understanding of the normal aging of attention. The unique contribution of the research is that brain metabolic changes will be examined in relation to attentional changes associated with both normal aging and DAT.