ATTENTION IN AGING AND EARLY ALZHEIMER'S DEMENTIA

阿尔茨海默型痴呆（DAT）的诊断是不确定的 在生活中，部分原因是难以区分 生理和认知变化伴随着正常老化， 与DAT早期阶段相关的那些。然而，最近， 局部脑葡萄糖代谢模式的改变 已经报道存在于早期DAT中。这些代谢 这些变化可能反映了大脑的代偿机制， 在正常老化和早期DAT中均有效，但 随着疾病的发展而下降。 这种补偿的强度 这些过程可能取决于注意力机制的效率， 特别是在应对日益增长的信息处理 要求。 提出了一个神经心理学模型， 这些发现与初步研究的结果表明， 简单的认知操作被保存在 早期DAT中的“注意力成本”。该模型提出， 低效的注意力机制代表了一种早期的功能性 DAT受损，是记忆中的潜在因素， DAT的认知缺陷。此外， 注意力相关的补偿机制在早期阶段 DAT可以预测随后认知能力下降的速度。 本研究的主要目的是对该模型进行评价 在一系列的六项研究中，四组受试者： 成年人，老年人，老年人严格的健康筛查 状态和DAT患者。 两种控制注意力的方法 - 对"探测"刺激的反应时间，以及 注意力-将被用来评估注意力的需求 在老化和早期DAT的认知操作。研究1和3将 研究注意力的两个方面--（一）注意力的需求 简单的认知操作和（ii）注意力的转换 从一个空间位置到另一个空间位置--在所有四组 科目 研究2和4将研究更复杂的特征， 年轻人和老年人的注意力机制。 研究5 将研究注意力机制之间的相互关系 在研究1和3中进行了研究， 通过18-FDG正电子发射断层扫描（PET）评估葡萄糖。 在研究6中，健康老年人和DAT受试者将每年接受 PET和研究1注意力测试的随访评价， 为期四年。 这项拟议中的研究将确定注意力的变化， 在DAT的早期阶段， 经过广泛的研究，也促进了对 注意力的变化伴随着正常的衰老。 结果应 有助于认知和生理的发展 早期诊断DAT的标志物。

The diagnosis of dementia of the Alzheimer type (DAT) is uncertain in life partly because of difficulties in discriminating the physiological and cognitive changes accompanying normal aging from those associated with the early stages of DAT. Recently, however, alterations in patterns of regional cerebral glucose metabolism have been reported to be present in early DAT. These metabolic changes may reflect compensatory brain mechanisms that are operative in both normal aging and in early DAT, but which break down as the disease progresses. The strength of such compensatory processes may depend upon the efficiency of attentional mechanisms, particularly in response to increased information-processing demands. A neuropsychological model is proposed that integrates these findings with the results of preliminary studies indicating that simple cognitive operations are preserved at greater "attentional cost" in early DAT. The model proposes that inefficient attentional mechanisms represent an early functional impairment in DAT and are underlying factors in the memory and cognitive deficits of DAT. Furthermore, the magnitude of attention-related compensation mechanisms in the early stages of DAT may predict the rate of subsequent cognitive decline. The major aim of the proposed research is to evaluate this model in a series of six studies in four groups of subjects: young adults, older adults, older adults rigorously screened for health status, and DAT patients. Two methods for manipulating attention- -reaction time to a "probe" stimulus, and covert shifts of attention--will be used to evaluate the attentional demands of cognitive operations in aging and early DAT. Studies 1 and 3 will examine two aspects of attention--(i) the attentional demands of simple cognitive operations and (ii) the switching of attention from one spatial location to another--in all four groups of subjects. Studies 2 and 4 will examine more complex features of these attentional mechanisms in young and older adults. Study 5 will examine interrelationships between the attentional mechanisms investigated in Studies 1 and 3 and cerebral metabolic rates for glucose as assessed by 18-FDG positron emission tomography (PET). In study 6 healthy elderly and DAT subjects will be given yearly follow-up evaluations on PET and the Study 1 attention tests for a period of four years. The proposed research will identify changes in attentional and physiological function in the early stages of DAT which have not been investigated extensively, and also advance understanding of attentional changes accompanying normal aging. The results should contribute to the development of cognitive and physiological markers for early diagnosis of DAT.