ATTENTION IN AGING AND EARLY ALZHEIMER'S DEMENTIA

阿尔茨海默型痴呆（DAT）的诊断是一个主要的 对临床医学的挑战，因为DAT的早期认知变化 很难与正常的成年人衰老相区分。 然而，正电子发射断层扫描（PET）研究表明， 脑代谢的地形图在早期阶段改变， 阿尔茨海默病（AD）。 这些研究表明， 在AD中，皮质皮质连接断开，特别是 后顶叶颞叶和额叶皮层 这些地区发挥着 在控制注意力功能中起着重要作用。 因此 受AD影响的皮质途径也实质上涉及 大脑皮层的注意力系统 最近的研究表明 注意力障碍可以在轻度痴呆患者中检测到， 在所有其他受AD影响的非记忆功能中存在缺陷。 一 提出了DAT中注意的神经解剖学模型，假设 分离但相互作用的皮质回路功能障碍， 不同形式的视觉选择性注意。 电路涉及 后顶叶、纹外区和联合颞区 假设调解基于位置、基于要素和基于对象的关系 选择性注意力。 一系列的6项DAT患者研究，健康，年龄匹配的对照， 建议正常的年轻人和老年人。 注意力和 静息脑代谢将在所有研究中可用; PET成像 与注意力相关的脑血流量将在一项研究中进行检查。 在早期DAT中，视觉选择性注意的两个主要方面是： 检查，基于位置和基于特征/对象的选择， 内隐视空间信息加工测验 注意力和视觉搜索。 这两种正常的年龄相关变化 视觉选择性注意方面也将进行研究。 将研究老龄化和DAT中基于位置的选择性注意， 前三个实验，包括一项纵向研究， 最初轻度DAT受试者在三年内的变化。 最后一 三个实验将研究基于特征和基于对象的选择性 注意及其与视觉空间注意的相互作用 注意力的神经解剖学模型将通过 (i)使用已知依赖于功能的注意力任务， 模型中表示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显像 在假定的新皮质区和它们的脑血流指数功能障碍 与轻度DAT中注意力表现的关系。 这项研究的意义在于， 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 （脑代谢和血流）及其相互关系是 对于开发早期诊断DAT的可靠标志物至关重要。 研究也将增进对注意力正常老化的了解。 这项研究的独特贡献在于， 将检查与两者相关的注意力变化 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.