Abstract
In this study, we discuss the principal carrier of speech information. Amplitude envelope of band-limited speeches was modeled by the proposed kernel function, producing two syntheses with modifications of either the maximal part or the minimal part. Change of envelope maxima deactivated the temporal cortices in the brain by means of near-infrared spectroscopy (NIRS) measurements, which were in accord with the reduction of percentage correct in a dictation test. We have hypothesized the integration of envelope maxima plays an important role in speech communication. As for NIRS methods, we considered the observation of hemoglobin concentrations as the most suitable index for the linguistic ability with following five advantages: (i) hemodynamic observation in the cerebral association cortices, (ii) completely non-invasive measurements with a brief start-up, (iii) a bedside equipment with silent operation and continuous monitoring, (iv) high flexibility in an experimental design because of tolerance for artifacts, and (v) low running costs without addition of supplies.
