Language-related neural activity measured by functional magnetic resonance imaging and magnetoencephalography

Neural activity related to orthographic, phonological, and lexico-semantic process was measured using functional magnetic resonance imaging (fMRI) and magnetoencephalography (MEC). Subjects were presented single Japanese katakana characters, pseudo-characters, and strings of real- or pesudo-characters, and were required visual-form, phonological, and semantic judgments. FMRI showed neural activation in the occipital and inferior temporal areas for the visual-form process, and in the left inferior frontal, superior temporal, and parietal areas for the phonological process. The semantic process is considered to share activation foci with the phonological process. The MEG experiments showed current dipoles, which reflect the neural activity, in the occipital and inferior temporal areas at a latency range of 120 to 180 ms, in the superior temporal area at a latency range of 320 to 350 ms, and in the inferior frontal area at a latency range of 310 to 460 ms. The results demonstrate that a combination of fMRI and MEG provides detailed information on spatio-temporal neural activity.