Language dominance assessment by means of fMRI: Contributions from task design, performance, and stimulus modality

We investigated the influence of different task demands, task designs, and presentation modalities on the functional MRI activation patterns during a language lateralization task in a group of 14 right-handed control subjects . A word classification task was presented as target task appropriate to ev oke language-related activation in the Inferior frontal gyrus (IFG). The ch oice of the contrasting baseline task was demonstrated to have a major Impa ct on the functional outcome: While a fixation baseline elicited activation s in the inferior frontal gyrus of both hemispheres, a nonsemantic perceptu al control task helped to isolate the relevant target task of word classifi cation. The modality of stimulus presentation did not influence the functio nal data: Auditory and visual presentation modes broadly evoked activations in similar brain regions during word classification. Minor differences in task performance and the side of the responding hand did not interfere with the functional activation patterns of the target task. On the basis of our results, a protocol of functional lateralization in the inferior frontal g yrus is suggested. (C) 2001 Wiley-Liss, Inc.