Determination of Hemispheric Language Dominance Using Functional MRI: Comparison of Visual and Auditory Stimuli

PURPOSE: To assess the difference between auditory and visual stimuli when determining hemispheric language dominance by using functional MRI. MATERIALS AND METHODS: In ten healthy adult volunteers (8 right-handed, 1 left-handed, 1 ambidextrous), motor language activation in axial slices of frontal lobe was mapped on a Simens 1.5T Vision Plus system using single-shot EPI. Series of 120 consecutive images per section were acquired during three cycles of task activation and rest. During each activation, a series of four syllables was delivered by means of both a visual and auditory method, and the volunteers were asked to mentally generate words starting with each syllable. In both inferior frontal gyri and whole frontal lobes, lateralization indices were calculated from the activated pixels. We determined the language dominant hemisphere, and compared the results of the visual method and the auditory method. RESULTS: Seven right-handed persons were left-hemisphere dominant, and one left-handed and one ambidextrous person were right-hemisphere dominant. Five of nine persons demonstrated larger lateralization indices with the auditory method than the visual method, while the remaining four showed larger lateralization indices with the visual method. No statistically significant difference was noted when comparing the results of the two methods(p>0.05). CONCLUSION: When determining hemispheric language dominance using functional MRI, the two methods are equally appropriate.