Untersuchung des dopaminergen Einflusses auf visuelle Aufmerksamkeit mittels EEG, fMRI und der Kombination beider Methoden mittels Einzel-trial-basierter Analyse

最近，大量的功能磁共振成像证据表明，多巴胺能中脑区域与人类对奖励预测刺激的处理有关。它们被认为或多或少地自动（“自下而上”）招募处理资源，以允许适当的响应。然而，问题仍然存在，多巴胺能中脑是否也在“自上而下”的注意力资源招募中发挥作用。这种自上而下的机制必须能够招募多巴胺能中脑，因为只有在对即将到来的情况的预知和没有任何相关的奖励偶然性的情况下。一项功能磁共振试验研究提供了支持这一假设的数据。在本实验中，目标刺激识别的难度被操纵，并通过目标前提示发出信号，导致多巴胺能中脑对困难任务的反应增强。为了能够令人信服地将这种激活解释为“自上而下”，有必要证明它是对提示本身的反应，而不是由目标处理任务本身产生的。因此，第一个项目提出了一项功能磁共振成像研究，以区分线索引起的活动和目标刺激引起的活动。第二个项目旨在建立一种新的方法，以弥合与注意力相关的fMRI激活和相应的脑活动电测量之间的差距，这些电测量来源于同时记录的EEG和fMRI测量的整合。

Recently, a large body of fMRI evidence has linked dopaminergic midbrain areas to the processing of reward-predicting stimuli in humans. These are thought to more or less automatically (“bottom-up”) recruit processing resources to allow for an adequate response. The question remains, however, whether the dopaminergic midbrain also plays a role in “top-down” recruitment of attentional resources. Such a top-down mechanism would have to be able to recruit the dopaminergic midbrain due only to foreknowledge about an upcoming situation and in the absence of any associated reward contingencies. A pilot fMRI study provides data in support of this hypothesis. In this experiment, the difficulty of target stimulus discrimination was manipulated, and signaled by a pre-target cue, which resulted in enhanced responses in the dopaminergic midbrain for the hard-task. In order to be able to convincingly interpret this activation as “top-down”, it is necessary to demonstrate that it arises in response to the cue by itself, rather than by the target processing task itself. Therefore, the first project proposes an fMRI study that distinguishes activity elicited by the cue from that elicited by the target-stimuli. The second project seeks to establish a novel approach to bridge the gap between the attention-related fMRI activations and corresponding electrical measures of brain activity, derived from the integration of simultaneously recorded measurements of EEG and fMRI.