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Ilg, Ruediger (2004): Neurale Mechanismen "intuitiver" Urteilsprozesse: Eine funktionelle kernspintomographische Untersuchung der impliziten Wahrnehmung semantischer Kohärenz. Dissertation, LMU München: Medizinische Fakultät



Many of our decisions depend on intuitive judgments that can be described as the capacity to implicitly evaluate the coherence of context-relevant information without being able to provide an explicit explanation. To study the neural mechanisms of implicit and explicit perception of coherence, we performed an event-related fMRI study using a semantic judgment task. Participants first had to judge whether three simultaneously presented words were coherent in the sense that they were all weakly related to a common associate or incoherent if they were not. Subsequently, participants had to provide, whenever possible, a solution word that was semantically related to the word triad, thereby allowing the following conditions: explicit perception of coherence (yes + solution), implicit perception of coherence (yes + no solution), and perception of incoherence (no + no solution). As a control condition, pseudoword triads were presented. fMRI data analysis was performed in SPM99 employing a random-effects model. Evaluation and perception of semantic coherence was predominantly associated with neural activity in left inferior and anteromedial prefrontal regions, in the temporal cortex, precuneus, and right cerebellum. Although no explicit solution was found, these regions were already active in the implicit condition, indicating that the implicit perception of semantic coherence is primarily based on the same structures as the explicit perception, but does obviously not suffice to retrieve an explicit answer. Implicit judgments of coherence, as opposed to explicit judgments, were correlated with an additional activation of bilateral parietal regions, the right superior temporal sulcus, and the left posterior parahippocampal gyrus. The common activation of the parietal association cortex and right superior temporal sulcus in the implicit condition supports the notion that intuitive judgments are based on an associative evaluation of information coherence.