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要旨

In the present study, we tested the hypothesis that brain activation would reflect perceptual choices. To probe this question, we used functional magnetic resonance imaging (fMRI) during a challenging fear–disgust, two-choice discrimination task. We investigated how moment-to-moment fluctuations in fMRI signals were correlated with perceptual choice by computing a choice probability index that quantified how well behavioral choice could be predicted by single-trial fMRI amplitude. Our analyses revealed that reporting a neutral face as "fearful" was associated with activation in a broad network of brain regions that process emotionally arousing stimuli, whereas reporting a neutral face as "disgusted" was associated with activation in a focused set of sites that included the putamen and anterior insula. Responses predictive of perceptual reports were not only observed at the group level but also at the single-subject level. Thus, voxel-by-voxel fluctuations in fMRI amplitude for an individual participant could
be used to reliably predict the perceptual choice of individual trials for that subject. In addition to the investigation of choice, we also isolated the neural correlates of decision making per se by using reaction time as an index of decision processes. Overall, our findings revealed that brain responses dynamically shifted according to perceptual choices. In addition, the neural correlates of decision making involved at least the anterior cingulate cortex, middle frontal gyrus, and inferior frontal gyrus/insula, consistent with recent proposals that decisions may emerge from distributed processes.