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。该提议的主要假设是，任务级控制在一定程度上是通过跨任务试验的持续活动来实现的，并且可以使用功能磁共振成像进行研究。这一假设是通过3个具体目标来解决的。具体目标1：完善分离持续和瞬态fMRI信号的范例设计和分析方法。主要假设是，混合块/事件相关范式可以被优化，以便从短暂的“试验相关”fMRI信号中准确和敏感地识别持续的“控制”信号。具体目标2：表征在试验中表现出持续活动的不同区域的功能属性。将测试三个一般假设：1)一些区域将在广泛的任务中表现出持续的活动，这意味着它们具有一般的控制功能；2)尽管存在这种共性，但对控制的可分离方面（例如，输入或响应选择）的操作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域相关的持续活动，暗示它们是特定领域控制的来源，或者是控制信号影响正在进行的试验相关处理的位置。具体目标3：利用持续信号的特性来解决特定于记忆检索的问题。几项情景检索研究显示了右侧额叶区域的激活，并提出这种活动可能与“检索模式”有关。对两个相关假设进行了检验：1)在需要“重新集体努力”或“重新集体模式”的条件下，会发现右侧额叶持续活动；2)右侧额叶的持续活动并不局限于“回忆”，当复杂的检索约束处于回忆和熟悉之间的“中间水平”时也会出现。作为一个整体，这些研究应该提高我们对大脑任务控制过程的理解。一些精神和神经疾病（如妥瑞氏综合征、额叶中风）与控制缺陷有关；更深入地了解与控制过程相关的神经机制，可能会比目前存在的更具体的诊断、预后或康复方法来解决这些困难。

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.