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

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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.