Verbal encoding fMRI paradigm adds complementary information to cerebral language lateralization

Title: Verbal encoding fMRI paradigm adds complementary information to cerebrallanguage lateralization.Purpose: To explore two conceptually different fMRI paradigms’ ability to lateralizelanguage.Methods: A verbal encoding paradigm and a word generation task were performed bysix patients (four right-handed) with therapy-resistant temporal lobe epilepsy (TLE),and by ten healthy individuals (five right-handed). FMRI laterality indices (LI) andlaterality curves for the anterior cerebral language regions were calculated. Typicallateralization was defined as left-hemisphere dominance, and a typical as bilateral orright-hemisphere dominance.Results: Both paradigms showed predominantly left-sided activation in the anteriorlanguage regions, with typical contralateral cerebellar activity. Thirteen out of sixteensubjects showed concordant language lateralization results for both paradigms.Two subjects, both left-handed, showed discordant language lateralization results.Laterality curves added information for individual subjects with uncharacteristicresults. The verbal encoding task showed overall more widespread activationcompared to the word generation task.Conclusion: Our results indicate valid language lateralization obtained by the fMRIverbal encoding paradigm for right-handed subjects. This offers the opportunity tosimultaneously study two cognitive functions, language and verbal encoding, usingone task. TLE is a network disease which predisposes afflicted patients to cortical reorganizationand inserting uncertainties regarding hemisphere dominance. Atypicallanguage representation in connection with left-handedness should be interpretedwith caution irrespective of which paradigm is chosen.Keywords: TLE, fMRI, handedness, lateralization index, language lateralization (Less)