Cognitive Control in Aging

这个项目的总体目标是更好地理解将意图转化为正常老龄化成年人的行动的过程：即所谓的执行控制过程。之前的行为研究表明，老年人的执行能力显著且逐渐降低。这个项目的具体目的是使用高密度电生理记录(事件相关电位)作为我们的依赖测量来研究从一个任务切换到另一个任务所涉及的执行过程。这使我们能够直接评估参与控制过程的区域网络中潜在的大脑动态。我们的初步数据表明，随着年龄的增长，任务切换的缺陷实际上可能不是由于前额叶皮质功能障碍，而是可能是由于顶叶皮质突起激活不足所致。这导致我们假设，衰老的核心缺陷实际上可能是无法维持注意力--这一过程与 顶叶激活。我们将使用的实验范式如下，是对已确立的任务转换范式的修改，允许与先前丰富的心理物理数据进行直接比较。在每一次试验中，都会提出一个由字母和数字组成的刺激。在连续的三次测试中，受试者将判断字母是元音还是辅音；在接下来的三次测试中，他们将判断数字是偶数还是奇数； 然后将重复这一序列。因此，受试者需要在字母分类任务和数字分类任务之间切换。他们的事件相关电位以及他们的行为表现(反应时间和错误率)将被记录下来。这将使我们能够比较受试者在三种类型的试验中的事件相关电位和行为表现：1)受试者从一个任务切换到另一个任务后的第一个试验(‘切换后’试验)；2)第二个试验 在任务转换之后(“嵌套”试验)；3)紧接在任务转换之前的试验(“转换前”试验)。因此，在“切换后”试验之前和/或期间，需要切换的执行进程将处于活动状态。因此，与这些过程相关的事件相关事件可以在a)“切换前”试验的后期阶段和/或b)在“切换后”试验的非常早期阶段找到。“嵌套”试验提供了比较“切换前”试验和“切换后”试验的基线。这些比较的结果将揭示年轻人和正常老年人任务转换所涉及的执行过程背后的神经机制。高密度的ERP记录和地形图将使我们能够评估额叶、顶叶和早期感觉区域对这些过程的相对贡献。

The overall goal of this project is to achieve a better understanding of the processes whereby intentions are translated into actions in normally aging adults: so-called 'executive control' processes. Previous behavioral research has suggested significant and progressive reductions in executive abilities in aging adults. The specific aim of this project is to study the executive processes involved in switching from one task to another using high-density electrophysiological recordings (event-related potentials (ERPs)) as our dependent measures. This allows us to directly assess the underlying brain dynamics across the network of areas involved in control processes. Our preliminary data suggest that the deficits in task-switching seen with aging may not in fact be due to prefrontal cortical dysfunction, a commonly held hypothesis, but rather, may result from deficient activation of parietal cortical processes. This has led us to hypothesize that a core deficit in aging may in fact be an inability to sustain attention- a process associated with parietal activations. The experimental paradigm we will use is as follows, and is a modification of a well-established task-switching paradigm, allowing for direct comparisons to the wealth of previous psychophysical data. On every trial, a stimulus comprised of a letter and a number will be presented. For three successive trials, subjects will judge whether the letter is a vowel or a consonant; for the next three trials, they will judge whether the number is even or odd; this sequence will then be repeated. Thus, subjects will be required to switch between a letter-categorization task and a number-categorization task. Their ERPs, as well as their behavioral performance (reaction times [RTs] and error rates), will be recorded. This will allow us to compare subjects' ERPs and behavioral performance on three types of trial: 1) the first trial after subjects have switched from one task to the other ('post-switch' trials); 2) the second trial after a task-switch ('nested' trials); 3) the trial immediately preceding a switch of task ('pre-switch' trials). Thus, the executive processes required to switch will be active before and/or during the 'post-switch' trial. The ERPs associated with these processes will therefore be found a) in the late stages of the 'pre-switch' trials, and/or b) in the very early stages of the 'post-switch' trials. The 'nested' trials provide a baseline against which to compare both the 'pre-switch' and the 'post-switch' trials. The results of these comparisons will shed light on the neural mechanisms underlying the executive processes involved in task switching in both young and normally aging adults. High-density ERP recordings and topographic mapping will permit us to assess the relative contributions of frontal, parietal and earlier sensory areas to these processes.