Funktionelle Organisation expressiver Sprache bei der mesialen Temporallappenepilepsie: fMRT Studie zum Vergleich hippocampaler Aktivierung bei freier Wortproduktion gegenüber Standard-Wortflüssigkeitsaufgaben

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Language is almost unique to the human species. It is of major relevance in every day life and social functioning. Verbal communication abilities crucially influence quality of life. Therefore, language is of high interest in clinical neuroscience. Expressive language function is classically associated with frontal lobe cortex (e.g. Broca`s area) but recent studies also point towards functional relevance of temporal lobe structures (e.g. the hippocampus). Mesial temporal lobe epilepsy (mTLE) constitutes a lesion model for hippocampal function. This fMRI project aims to study word fluency as an expressive language function in mTLE patients. Word fluency is usually investigated with word generation to a given initial letter (phonemic fluency) or to a given category (semantic fluency). However, free, unrestricted word generation has shown hippocampal activation on fMRI in healthy volunteers. This hippocampal activation was attenuated in schizophrenia, which is accompanied (among other pathology) by structural abnormalities of temporal cortex. Patients with mTLE of the left hemisphere, which is usually language dominant, share further characteristics with schizophrenia patients: Both exhibit verbal memory deficits and have a higher probability of atypical (bilateral or right hemispheric) language dominance. Atypical language dominance is considered a result of functional reorganization processes due to neural plasticity. What leads to such reorganisation is not yet clearly understood. This study intends to add substantial knowledge about the role of the hippocampus in expressive language and aims to better characterize determinants of cortical language representation in patients with specific brain lesions. Language fMRI is frequently applied to patients who are candidates for epilepsy surgery to preoperatively identify eloquent cortex. As a clinical impact, results of the proposed study shall contribute to improve current paradigms for fMRI language assessment.