Abstract
Functional magnetic resonance imaging (fMRI) using easy verb generation tasks can reliably locate the expressive language area, whereas magnetoencephalography (MEG) can sensitively detect the receptive language area irrespective of cerebral blood flow abnormalities. By combining the advantages of these two approaches, we established a reliable method for identifying the global language dominance in patients with pathological brain conditions. This functional brain mapping co-utilizing fMRI and MEG was performed in 117 patients. Ninety-seven patients further underwent the Wada test to confirm language dominance. A total of 87 patients were analyzed using useful data from both the combined method and the Wada test. fMRI with the verb generation task typically showed prominent activation in the inferior and middle frontal gyri. Reading a 3-letter Japanese word and judging silently whether it is "abstract" or "concrete" was originally designed as the task for MEG. The calculated dipoles typically clustered in the superior temporal region and the fusiform gyrus of the dominant hemisphere. In 85 of 87 patients who underwent successful MEG and fMRI, the combination method results for language dominance matched the Wada test. Two cases showed expressive and receptive language areas dissociated into bilateral hemispheres, which were also carefully validated by an invasive procedure. The results demonstrate that this non-invasive and repeatable method is not only highly reliable in determining language dominance, but can also locate the expressive and receptive language areas separately. The method may be a potent alternative and comparable to invasive procedures, and useful in identifying language dominance with high reliability.
