Functional Magnetic Resonance Study. Vocal Tasks In Functional Magnetic Resonance Study And Character Regularity Effect

Objective: To develop more reliable and effective algorithms for elimination of the artifacts induced by overt responses in functional magnetic resonance imaging (fMRI). To study the neural correlates of the regularity effect in reading Chinese characters, neural basis of the transformation between orthography and phonology of Chinese character.Methods: Eight subjects performed Chinese characters reading tasks during scanning. One hundred and sixty Chinese characters, 80 regular and 80 irregular characters, severed as stimuli. The number of stokes, radicals, frequency and imagiability were matched amongst the stimuli.In the part one of this study, three algorithms were performed to correct the artifacts induced by overt response, and brain activations during overt and covert responses were compared.In the part two, using the most reliable algorithm developed in the part one, we characterized the neural basis of the regularity effect during overt reading of Chinese characters.Results: The part one of the study showed that using the traditional algorithms there were serious artifacts in activation maps of reading aloud, and most of these artifacts were eliminated by new algorithms developed in the present study. Activation in Broca's area and its right homogeneous area, right superior temporal gyms, and dorsal lateral frontal gyrus was significantly stronger during overt response than during covert responses.The part two demonstrated that both irregular and regular stimuli activated Broca's area and its right homogeneous area, Wernicke's area, bilateral premotor cortex, supplementary motor area (SMA), LMFG, anterior cingulated cortex(ACO),anterior basal temporal gyms, bilateral insular, extrastriate cortex, whereas stronger activation was found in the posterior parietal lobe, ACO, right insular, and LMFG during irregular stimuli.Conclusions: The artifacts induced by overt responses can be effectively corrected using appropriate algorithms, suggesting that it is feasible to use fMRI for investigation of neural basis of overt responses. It is also suggested that one should be caution to generalize fMRI findings of covert tasks to those of overt tasks, since the brain activation patterns are not identical in two conditions. Relative to the processing of orthography mapping onto phonology in alphabetic languages, reading Chinese characters appears to depend on a set of specific brain regions, among which the left posterior parietal lobe, anterior cinglulated cortex (AC), right insular, and LMFG play a more important role.