ATTENTION IN AGING AND EARLY ALZHEIMER'S DEMENTIA

阿尔茨海默型痴呆(DAT)的诊断尚不确定 在生活中，部分原因是很难区分 伴随着正常衰老的生理和认知变化 与DAT早期阶段相关的疾病。然而，最近， 脑局部葡萄糖代谢模式的改变 已经被报道出现在DAT的早期。这些新陈代谢 变化可能反映了代偿性大脑机制，即 在正常衰老和早期DAT中均可操作，但会破裂 随着疾病的发展而下降。这种补偿性的力量 过程可能取决于注意机制的效率， 尤其是在信息处理能力增加的情况下 要求。提出了一个神经心理学模型，该模型集成了 这些发现与初步研究的结果表明 简单的认知操作在更大的 早期DAT的“注意成本”。该模型提出， 低效的注意机制代表了早期的功能 DAT中的损害和是记忆和 DAT的认知缺陷。此外，其大小 注意相关补偿机制在早期阶段的应用 DAT可以预测随后认知功能减退的速度。 建议研究的主要目的是对该模型进行评估。 在对四组受试者进行的一系列六项研究中：杨 成年人、老年人、老年人严格进行健康筛查 状态和DAT患者。操纵注意力的两种方法- --对“探测”刺激的反应时间，以及隐蔽的 注意力--将用来评估学生的注意需求 衰老和早期DAT中的认知操作。研究1和研究3将 考察注意的两个方面--(一)注意要求 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 研究对象。研究2和研究4将检查更复杂的特征 年轻人和老年人的这些注意机制。研究5 将研究注意机制之间的相互关系 在研究1和研究3中进行的研究以及 18-FDG正电子发射断层扫描(PET)测定血糖。 在这项研究中，6名健康老年人和DAT受试者将每年接受一次治疗 对正电子发射计算机断层扫描和研究1注意力测试的随访评估 四年的时间。 这项拟议的研究将确定注意力和 DAT早期的生理功能 进行了广泛的调查，也加深了对 伴随着正常衰老的注意力变化。结果应该是 有助于认知和生理的发展 DAT早期诊断的标志物。

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.