The Study of Task-Level Control Signals Using fMRI

描述(由申请人提供)：认知神经科学的一个主要问题是如何组织特定的神经通路来完成任务。这一建议的主要假设是，任务级别的控制部分是通过跨任务试验持续的活动来实现的，并且可以使用功能磁共振成像进行研究。这一假设是通过三个具体目标来阐述的。具体目标1：改进用于分离持续和瞬时功能磁共振信号的范例设计和分析方法。主要的假设是，混合的区块/事件相关范式可以被优化，以准确和灵敏地从瞬时的“试验相关”fMRI信号中识别持续的“控制”信号。具体目标2：描述不同区域在试验中表现出持续活动的功能属性。将检验三个一般假设：1)一些区域将表现出跨越广泛任务的持续活动，暗示它们在一般控制功能中；2)尽管存在这种共性，但控制的可分离方面的操纵(例如，输入或反应选择)将不同地影响这些区域的特定子集；3)一些区域将显示与特定任务领域相关的持续活动，暗示它们是领域特定控制的来源，或者是控制信号影响正在进行的与试验相关的加工的地点。具体目标3：利用持续信号的性质来解决记忆提取特有的问题。一些间歇性的提取研究表明，右额叶区域被激活，有人认为这种活动可能与“提取模式”有关。检验了两个相关的假设：1)右额叶持续活动存在于需要“再集体努力”或“再集体模式”的条件下；2)右额叶持续活动不是特定于“回忆”的，但当复杂的提取限制被置于回忆和熟悉之间的“中间水平”时也会出现。作为一个整体，这些研究应该会提高我们对大脑中任务控制过程的理解。一些精神和神经疾病(如抽动症、额叶中风)与控制缺陷有关；对与控制过程相关的神经机制的深入了解可能会使这些困难比目前存在的更具体的诊断、预后或康复方法。

DESCRIPTION (provided by applicant): A major issue in cognitive neuroscience is how specific neural pathways are organized for task performance. The major hypothesis of this proposal is that task-level control is implemented, in part, by activity sustained across task trials, and can be studied using fMRI. This hypothesis is addressed through 3 Specific Aims. Specific Aim 1: To refine paradigm designs and analysis methods for separating sustained and transient fMRI signals. The main hypothesis is that the mixed block/event related paradigm can be optimized for the accurate and sensitive identification of sustained "control" signals from transient "trial-related" fMRI signals. Specific Aim 2: To characterize the functional attributes of different regions exhibiting sustained activity across trials. Three general hypotheses will be tested: 1) Some regions will exhibit sustained activity across a wide range of tasks, implicating them in general control functions; 2) In spite of this commonality, manipulation of separable aspects of control (e.g., input or response selection) will differentially affect specific subsets of these regions; 3) Some regions will show sustained activity related to specific task domains, implicating them as sources of domain specific control, or as sites at which control signals affect ongoing trial-related processing. Specific Aim 3: To use properties of sustained signals to address issues specific to memory retrieval. Several episodic retrieval studies have shown activation of right frontal regions, and it has been proposed that this activity may be related to "retrieval mode". Two related hypotheses are tested: 1) Right frontal sustained activity will be found across conditions that demand "re-collective effort" or "re-collective mode"; 2) The right frontal sustained activity will not be specific to "recollection", but will also be present when complex retrieval constraints are placed at "intermediate levels" between recollection and familiarity. As a group, these studies should improve our understanding of task control processes in the brain. Several psychiatric and neurological diseases (e.g., Tourette's syndrome, frontal lobe strokes) have been related to deficits of control; a deeper understanding of the neural mechanisms related to control processes may allow more specific diagnostic, prognostic, or rehabilitative approaches to these difficulties than currently exist.