Functional Organization of Posterior Parietal Cortex

描述(申请人提供)：信息的短期维持是人类认知的一个基本方面，它受到各种精神健康疾病的影响，包括：精神分裂症、ADHD、药物滥用障碍、阿尔茨海默病、帕金森氏病和艾滋病相关痴呆症。更深入地了解短期维持的基本神经机制将有助于改善这些疾病的诊断、预后和治疗程序。这项拟议的研究将集中在三种类型的短期维持上：感觉注意力、运动意图和工作记忆。人们普遍认为，在延迟时间间隔内持续的神经活动是大脑执行这三个认知过程的机制。后顶叶皮质(PPC)已经成为与注意力、意图和工作记忆相关的持续延迟期活动的研究重点。拟议中的实验将使用功能磁共振成像来测量受试者的皮质活动，同时他们执行三项密切相关但互补的任务，这些任务在对感觉注意、运动意图和工作记忆的依赖方面存在差异。在第一个任务中，受试者将眼球运动到记忆中的位置。在第二个任务中，受试者将在提示的位置检测到亮度的降低。在第三个任务中，受试者将察觉到目标记忆位置的微小变化。这三个任务对意图、注意力和工作记忆提出了不同的要求。第一个任务强调运动意图；在这个任务中，受试者将眼球移动到记住的位置，而在另外两个任务中，他们必须准确地保持注视。第二个任务强调感官注意；在这个任务中，受试者将注意到不断被照亮的目标，而在另外两个任务中，他们将记住不再可见的目标的位置。第三项任务强调空间工作记忆；在这项任务中，受试者会记住目标的位置，以便以后进行比较，而其他两项任务不涉及空间比较。这三个任务将被用来实现两个中心目标，即人和猴子的PPC之间的同源性以及人类PPC在感觉注意、运动意图和工作记忆中的功能作用。第一个目标是定义几个皮质区域中的每一个，使用测量注意力、意图和工作记忆的地形图表征的实验方案。第二个目的是验证这样的假设，即这些现在预先定义的人类皮质区域在功能上与猴子PPC中的皮质区域(特别是猴区LIP)同源，并测试这三个任务中每一个任务的行为表现取决于这些人类皮质区域中延迟期活动水平的假设。

DESCRIPTION (provided by applicant): Short-term maintenance of information is a fundamental aspect of human cognition that is compromised by a wide variety of mental health disorders including: Schizophrenia, ADHD, substance abuse disorders, Alzheimer's disease, Parkinson's disease, and AIDS related dementia. A deeper understanding of the basic neural mechanisms underlying short-term maintenance will lead to improved diagnostic, prognostic, and therapeutic procedures for these disorders. The proposed research will focus on three types of short-term maintenance: sensory attention, motor intention, and working memory. It is widely believed that sustained neural activity during a delay interval is the mechanism by which the brain performs these three cognitive processes. Posterior parietal cortex (PPC) has emerged as a particular focus for research on sustained delay-period activity related to attention, intention, and working memory. The proposed experiments will use fMRI to measure cortical activity in human subjects while they perform three closely related but complementary tasks that differ in their dependence on sensory attention, motor intention, and working memory. In the first task, subjects will perform an eye movement to a remembered location. In the second task, subjects will detect a luminance decrement at a cued location. In the third task, subjects will detect a small shift in the remembered location of a target. These three tasks place differential demands on intention, attention, and working memory. The first task emphasizes motor intention; in this task subjects will make eye movements to remembered locations whereas in the other two tasks they will have to accurately hold fixation. The second task emphasizes sensory attention; in this task subjects will attend to targets that are constantly illuminated whereas in the other two tasks they will remember the locations of targets that are no longer visible. The third task emphasizes spatial working memory; in this task subjects will remember the location of a target for later comparison whereas no spatial comparison is involved in the other two tasks. These three tasks will be used to achieve two central aims concerning the homology between human and monkey PPC and the functional role of human PPC in sensory attention, motor intention, and working memory. The first aim is to define each of several cortical areas, using experimental protocols that measure topographic representations of attention, intention, and working memory. The second aim is to test the hypothesis that these now pre-defined human cortical areas are functionally homologous to cortical areas in monkey PPC (particularly monkey area LIP), and to test the hypothesis that behavioral performance of each of the three tasks depends on the level of delay-period activity in these human cortical areas.