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Non-invasive assessment of hemispheric language dominance by optical topography during a brief passive listening test: A pilot study

Stefano Bembich, Sergio Demarini, Andrea Clarici, Stefano Massaccesi, Domenico Loenardo Grasso

Med Sci Monit 2011; 17(12): CR692-697

DOI: 10.12659/MSM.882128

Background:    The Wada test is usually used for pre-surgical assessment of language lateralization. Considering its invasiveness and risk of complications, alternative methods have been proposed but they are not always applicable to non-cooperative patients. In this study we explored the possibility of using optical topography (OT) – a multichannel near-infrared system – for non-invasive assessment of hemispheric language dominance during passive listening.
    Material/Methods:    Cortical activity was monitored in a sample of healthy, adult Italian native speakers, all right-handed. We assessed changes in oxy-haemoglobin concentration in temporal, parietal and posterior frontal lobes during a passive listening of bi-syllabic words and vowel-consonant-vowel syllables lasting less then 3 minutes. Activated channels were identified by t tests.
    Results:    Left hemisphere showed significant activity only during the passive listening of bi-syllabic words. Specifically, the superior temporal gyrus, the supramarginal gyrus and the posterior inferior parietal lobe were activated.
    Conclusions:    During passive listening of bi-syllabic words, right handed healthy adults showed a significant activation in areas already known to be involved in speech comprehension. Although more research is needed, OT proved to be a promising alternative to the Wada test for non-invasive assessment of hemispheric language lateralization, even if using a particularly brief trial, which has been designed for future applications with non-cooperative subjects.

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