| The Intracarotid Amobarbital Test (IAT) still is the most widely used procedure for the pre-surgical evaluation of language lateralization in epileptic patients. However, this technique is invasive and traumatic, especially for children. Recently, imaging techniques such as fMRI, have been used as less, or non-invasive alternatives. However, these methods have their own limitations, which render their application difficult in paediatric populations and patients with important cognitive or behavioural problems. Thus, developing new alternative techniques for children is crucial. The present work intended to explore the applicability of evoked-related potentials (ERP) recorded using high density electrophysiology (HDE) and near infrared spectroscopy (NIRS) in the assessment of language lateralization in children and special populations.;The second study was carried out to investigate the applicability of NIRS in the lateralization of language functions in healthy and epileptic adults and children. The results showed that a simple verbal fluency task was sufficient to induce a clear cerebral activation in the language areas in all participants. Moreover, NIRS findings were congruent with IAT and fMRI results. The technique also allowed for the identification of individual patterns of language distribution in the brain, which could be part of a functional reorganization, induced by the epileptic disorder. Thus, NIRS seems to be a promising technique for the assessment of language lateralization in epileptic patients.;In the third study, NIRS was used to explore both expressive and receptive language lateralization in a young boy with refractory epilepsy in whom IAT and fMRI had failed to yield conclusive results. This child showed expressive language organization in the left frontal area and an atypical bilateral cerebral activation pattern of receptive language. These results indicate that NIRS can be an effective method to localize both expressive and receptive language areas in children.;The aim of the fourth study was to localize the epileptogenic zone in addition to exploring language lateralization in a young epileptic boy. To do this, simultaneous recordings of NIRS and electroencephalography (EEG) were carried out. NIRS results revealed localization of expressive language in Broca's area. Furthermore, exploration of the epileptogenic zone, using simultaneous NIRS and EEG recordings, showed a significant cerebral activation in right frontal regions. Again, an excellent concordance was obtained with other functional imaging techniques.;In a first study, ERP recorded using HOE were used in healthy adults to elicit a N400 in response to verbal and nonverbal stimuli and to identify the anatomical sources of both the "verbal N400" and the "nonverbal N400". The results revealed that both deflections are distinct components induced by different cerebral areas. In fact, the "verbal N400" was found to be generated in the left superior temporal gyrus whereas the "nonverbal N400"originated in the right temporal regions. Although these findings are still preliminary, this work points to the potential usefulness of ERP recorded using HDE in the exploration of language lateralization.;Although the results need to be replicated in larger samples, the findings of this thesis show the potential of high density electrophysiology and near infrared spectroscopy to become non-invasive alternatives to the IAT in the exploration of language lateralization. Both techniques seem to be suitable for children and mentally-challenged patients. Furthermore, combining the two techniques proves to be promising for the simultaneous localization of language functions and the epileptogenic zone in epileptic children slated for surgery.;Key-words: epilepsy, pre-surgical evaluation, N400, verbal incongruities, environmental sounds, expressive language, receptive language, epileptogenic zone, evoked-related potentials (ERP), near infrared spectroscopy (NIRS). |
