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This document is a summary of literatures [12, 17, 18, 19, 22, 23]. We have a highly interest in near-infrared spectroscopy (NIRS) method or optical topography (OT) of multiple measurements with following five advantages : (i) completely non-invasive measurements with a brief start-up, (ii) a bedside equipment with silent operation and continuous monitoring, (iii) hemodynamic observation in the cerebral association cortices, (iv) high flexibility in an experimental design because of tolerance for artifacts, and (v) low running costs without addition of supplies. We are planning to measure cerebral blood volume (CBV) change in the auditory association cortices, which are closely related to linguistic ability, because many neuroimaging studies with spatial resolution have commonly reported the left dominance of cerebral blood flow (CBF) and/or blood oxygenation level dependent (BOLD) contrast during language-oriented tasks or even a simple listening to speeches. Various synthesized speeches may reveal what structure in waveforms plays an essential role in the neurophysiological speech recognition by means of a semi-quantified index of lateral oxygenation.