Investigating cognitive functions mediated by ventral and dorsal striatum

这项研究的目的是为了更好地理解学习、记忆和决策是如何完成的，以及产生这些复杂认知过程的大脑区域。这个项目的独特之处在于，它专注于一种被称为纹状体的皮层下结构对这些高阶功能的贡献。大脑皮层下结构是由深层到外层形成大脑皮层的细胞群形成的。这些皮层下的大脑结构比皮层进化得更早，通常与更原始或自动化的功能有关。纹状体被广泛理解为调节运动。然而，纹状体在思维过程中也扮演着越来越重要的角色。事实上，纹状体分为腹侧（即朝向腹部）和背侧（即朝向背部）两个部分，每个部分似乎都是一套不同的认知过程的基础。然而，这些列表远未完全定义。使用功能性磁共振成像（fMRI），可以测量血流量作为区域大脑活动的指标，以及各种学习、记忆和决策测试，目的是更好地定义腹侧和背侧纹状体执行的特定过程。这个概念是，通过比较一些优先涉及这些区域的技能、任务或条件，并了解这些场景的共同点，我们可以推断腹侧纹状体和背侧纹状体执行的特定计算。回顾现有的文献，以及我自己最近的研究，预期腹侧纹状体将涉及一般的学习过程，而不限于从奖励中学习的具体情况，就像之前认为的那样。相比之下，背纹状体并没有被预测为调节早期学习，尽管它之前被认为与学习运动反应或技能有关。相反，人们期望背纹状体是决策过程的基础，特别是在模棱两可的情况下。本研究的进一步目的将是阐明这些皮层下结构如何与皮层区域相互作用，并了解腹侧纹状体和背侧纹状体完成的特定功能。为了实现这一目标，我们将采用不同的fMRI分析，这些分析侧重于通过功能或解剖结构连接的区域（例如，连接性分析，扩散张量成像）或在功能方面彼此分离的区域（例如，独立组件分析）。另一种将腹侧纹状体和背侧纹状体完成的特定功能与与其相连的皮层区域分离的方法是，暂时使已知与纹状体合作的皮层区域失去活动，并观察行为和fMRI活动的变化。在提出的研究中，在参与者在fMRI扫描仪中执行特定任务之前，将使用一种称为重复经颅磁刺激的技术来暂时和可逆地抑制皮质小而定位良好的区域的功能。综上所述，本研究计划旨在阐明腹侧纹状体和背侧纹状体独立于其皮层伙伴进行的特定认知操作。这项研究有可能增强当前关于注意力、学习和决策的理论。这些理论最终具有广泛的影响，为公共安全实践（例如交通/驾驶员安全）提供信息，指导教育政策和实践，并可应用于理解和改进工业或法律等背景下的决策。

The aim of the proposed research is to better understand how learning, memory, and decision making are accomplished and the brain regions that produce these complex cognitive processes. This project is unique in focusing on the contributions of a subcortical structure called the striatum to these higher-order functions. Subcortical brain structures are formed by clusters of cells deep to the outer cell layers that form the cerebral cortex. These subcortical brain structures evolved earlier than the cortex, and are generally implicated in more primitive or automated functions. The striatum is widely understood to regulate movements. Increasingly, however, the striatum is ascribed a role in thinking processes as well. In fact, the striatum separates into ventral (i.e., toward the belly) and dorsal (i.e., toward the back) parts, with each appearing to underlie a different set of cognitive processes. These lists are far from fully defined, however. Using functional magnetic resonance imaging (fMRI), which allows measurement of blood flow as an index of regional brain activity, and various tests of learning, memory, and decision making, the aim is to better define the specific process(es) performed by ventral and dorsal striatum. The notion is that by comparing a number of skills, tasks, or conditions that preferentially engage each of these regions, and understanding what these scenarios have in common, we can deduce the specific computation(s) performed by ventral and dorsal striatum. From reviewing the existing literature, as well as my own recent research, the expectation is that ventral striatum will be implicated in general learning processes, not limited to the specific case of learning from reward, as had been thought. In contrast, dorsal striatum is not predicted to mediate early learning, though it has previously been linked to learning motor responses or skills. Rather, the expectation is that the dorsal striatum underlies decision making processes, particularly in ambiguous contexts. A further aim of this research will be to clarify how these subcortical structures interact with regions of cortex, and to understand the specific functions accomplished by ventral and dorsal striatum. Toward this goal, we will employ different fMRI analyses that focus on regions that are connected by their function or anatomy (e.g., connectivity analyses, diffusion tensor imaging) or that segregate from one another in terms of function (e.g., independent components analyses). An additional means for dissociating the specific functions accomplished by ventral and dorsal striatum relative to cortical regions to which they are connected, is to temporarily disable activity in cortical regions that are known to partner with striatum and to observe how behaviour and fMRI activity changes. In the proposed research, temporarily and reversibly depressed function of small and well-localized regions of cortex will be accomplished using a technique called repetitive transcranial magnetic stimulation, before participants perform specific tasks in the fMRI scanner. Taken together, this research programme aims to clarify the particular cognitive operations performed by the ventral and dorsal striatum, independent of their cortical partners. This research has the potential to augment current theories of attention, learning, and decision making. These theories ultimately have broad implications, informing public safety practices (e.g., traffic/driver safety), guiding educational policies and practices, and can be applied to understand and improve decision making in contexts such as industry or law.