Age-associated non-selective neural activations

描述（由申请人提供）：拟议的项目旨在研究老年人在情景记忆任务中半球不对称减少的本质。在当前的项目中，提出了三个事件相关的fMRI实验，试图表征介导年龄相关的非选择性神经激活的功能机制和认知过程（即年轻人参与的大脑区域的招募）。目前出现了两种观点来解释这种与年龄相关的神经激活。根据补偿观点，与年龄相关的半球不对称减少可能有助于抵消与年龄相关的神经认知衰退。根据去分化观点，年龄相关的不对称减少反映了招募专门神经机制的困难。为了区分这些观点，我们结合了各种方法，包括受试者之间的比较（即高功能与低功能的老年人），受试者内部的比较（例如随后记住的项目与随后忘记的项目），以及检索需求不同的条件的比较。在实验1中，我们试图通过在单个实验中结合受试者内部和受试者之间的比较来调和先前在衰老情景编码研究中观察到的结果。实验二探讨了不同检索需求条件下青年的检索相关神经激活。在实验3中，我们研究了年龄相关的非选择性激活是否延伸到中颞叶（MTL）区域，使用的任务（即联想识别）对MTL的要求比以前用于研究这一问题的任务更高。

DESCRIPTION (provided by applicant): The proposed project aims to examine the nature of hemispheric asymmetry reductions in older adults during tasks of episodic memory. In the current project, three event-related fMRI experiments are proposed which attempt to characterize the functional mechanisms and cognitive processes mediating age-related non-selective neural activations (i.e. recruitment of brain regions beyond those engaged by young adults). Two views have emerged to account for such age-associated neural activations. By the compensation view, age-related hemispheric asymmetry reductions may help to counteract age-related neurocognitive decline. According to the dedifferentiation view, age-related asymmetry reductions reflect a difficulty in recruiting specialized neural mechanisms. To differentiate between these views, we combine a variety of methods, including between-subjects comparisons, (i.e. high- versus low-functioning older adults), within-subject comparisons (e.g. subsequently remembered versus subsequently forgotten items), and comparisons of conditions which vary in their retrieval demand. In Experiment 1, we attempt to reconcile the results observed in previous episodic encoding studies of aging by combining within- and between-subjects comparisons in a single experiment. In Experiment 2, we explore retrieval-related neural activations in young adults under conditions which differ in retrieval demand. In Experiment 3, we investigate whether age-related non-selective activations extend to medial-temporal lobe (MTL) regions using a task (i.e., associative recognition) that places greater demands on the MTL than tasks previously used to examine this issue.