gms | German Medical Science

Objective: Variations of activated language areas are examined dependent on the language, the paradigm and the mode of stimulation used in fMRI (functional magnetic resonance imaging) and MEG (magnetoencephalography) measurements.

Methods: MEG measurements were carried out with a 2x37 channel biomagnetic system (Magnes II, 4-D Neuroimaging). Localization was performed by 1-dipole fit. For fMRI we used a 1.5T MR scanner with echo planar imaging (Sonata, Siemens Medical Solutions) and a block paradigm with 180 measurements in 6 blocks (rest alternating with activation, 25 slices, 3mm thickness & resolution TR=2470, TE=60). 162 Patients with tumours neighbouring speech related cortical areas and volunteers were examined. During measurement they had to perform verbal tasks. For each patient MEG measurements with two paradigms were performed while in fMRI four paradigms were used. Paradigms differed in the extent of grammatical effort and involvement of receptive and expressive language function. In 9 subjects 2 languages were tested. Measurement position was identical for all paradigms of a measurement modality.

Results: Usually, activations were found at identical regions for the languages of multilingual subjects in all language areas. In general, Variations due to different paradigms were small. A difference was found dependent on presentation mode of the language content. Acoustic language stimulation showed more bilateral activity than visually presented stimuli. Stimulation with Kanji signs showed some other activation than languages with letters. In a patient where the second language was acquired during a time when the lesion was already present differences occurred due to reorganisation (brain plasticity). We observed a shift of the second language to the former non dominant hemisphere. Early activation of picture naming differs from reading words in MEG.

Conclusions: In general similar language localizations were obtained from all paradigms. In multilingual patients especially when deciding the laterality it is necessary to test all respective languages, if the languages were acquired in periods with and without the lesion being existent. We found it useful to test several paradigms. The combination of MEG and fMRI increases the reliability of the language localizations. If possible visual stimulation should be used.