Abstract
Accurate localization of language processing areas is critical in patients undergoing epilepsy surgery. In this study, we aimed to use functional magnetic resonance imaging (fMRI), which is a non-invasive mapping method, to establish a panel of tasks investigating patients’ language function. We developed six tasks, including a series of progressive comprehension tasks from words, sentence to text, a verb generation task that can detect subtle left-brain activation, an auditory comprehension task that explored the temporal language-related areas, and a visual object-naming task provided for poorly educated patients. We successfully located the language cortex in 40 patients, and subsequently determined hemispheric dominance for the Chinese language. Our results showed a concordance between fMRI tasks and electrical cortical stimulation. The consistency across tasks revealed by the laterality index, as well as the concordance between the surgical outcomes and the results of localization, suggested the validity of our fMRI tasks. Our fMRI tasks also corroborate and extend the finding that the left middle frontal area (BA 9) plays an important role in reading Chinese.
Highlights
Several approaches have been used to clinically identify the specific cortices and/or dominant hemisphere associated with language, including electrocortical stimulation mapping (ESM) through intracranial electrodes (Ojemann et al, 1989), transcranial magnetic stimulation (Epstein, 1998), the intracarotid sodium amobarbital perfusion test (Wada test) (Strauss and Wada, 1983; Baxendale, 2009), and functional neuroimaging techniques (Bookheimer, 2002).The Chinese language differs from alphabetical languages such as English in many aspects, including orthography, phonology, and syntax (Kochunov et al, 2003; Qiu et al, 2006)
When we reported the results of individual patients to the surgeons, we did not emphasize the lateralization of language processing
We used the concordance between the functional magnetic resonance imaging (fMRI) and the ESM, lateralization indices (LI) and its consistency across tasks to measure the validity of the design of our tasks
Summary
Several approaches have been used to clinically identify the specific cortices and/or dominant hemisphere associated with language, including electrocortical stimulation mapping (ESM) through intracranial electrodes (Ojemann et al, 1989), transcranial magnetic stimulation (Epstein, 1998), the intracarotid sodium amobarbital perfusion test (Wada test) (Strauss and Wada, 1983; Baxendale, 2009), and functional neuroimaging techniques (Bookheimer, 2002). The Chinese language differs from alphabetical languages such as English in many aspects, including orthography, phonology, and syntax (Kochunov et al, 2003; Qiu et al, 2006). Brain activation in processing the Chinese language is expected to differ from that in processing English. Valaki et al (2004) suggested that there was greater symmetry in brain hemispheric dominance in Mandarin speakers evaluated by magnetoencephalography (MEG), whereas asymmetry was obvious in English and Spanish speakers (Valaki et al, 2004).
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