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Zusammenfassung:
Functional MRI studies (fMRI) are based on the blood-oxygenation-level-dependent effect (BOLD) that arises in brain areas where neuronal activity takes place (Ogawa et al., 1990, 1993). BOLD induces changes in the local magnetic susceptibility and these can be measured by Gradient Echo (GE) Echo-Planar-Imaging (EPI). The fMRI signal thus observed consists of a complex value, which can be subdivided into a magnitude and a phase value, but in most fMRI studies the phase signal is discarded and only the magnitude changes are used to detect the activated brain areas.
