Assessing cerebral representations of short and long vowel categories by NIRS

Abstract

The present study examined cerebral representations of Japanese long and short vowel categories with near-infrared spectroscopy (NIRS) by measuring the hemodynamic changes. Results showed that NIRS could capture phoneme-specific information. The left side of the auditory area showed large hemodynamic changes only for contrasting stimuli between which the phonemic boundary was estimated, but not for stimuli differing by an equal duration but belonging to the same phoneme category. Left dominance in phoneme processing was also confirmed for the across-category stimuli. These findings indicate that the Japanese vowel contrast based only on duration differences is dealt with in the same language-dominant hemisphere as other spectrally varying phonemic categories, and that the cortical activities related to its processing can be detected with NIRS.

Neural Attunement Processes in Infants during the Acquisition of a Language-Specific Phonemic Contrast

“…3A). This is in contrast to the response pattern of the adults (Minagawa-Kawai et al, 2002), in which the evoked responses were found in limited channels in the auditory area (Fig. 3C).…”

“…However, at this age, the cerebral response was not left dominant, and its phoneme specificity disappeared at 10 -11 months. The phonemic response did not become consistently left lateralized until after 12 months, similar to native adults (Minagawa-Kawai et al, 2002;Jacquemot et al 2003).…”

“…As previous NIRS studies have successfully detected cortical activities related to the phonemic or prosodic changes in adults and infants (Sato et al, 1999;Minagawa-Kawai et al, 2002;Furuya and Mori, 2003;Pena et al, 2003;Homae et al, 2006), the present study captured a developmental process in which the neural activations of Japanese infants changed from a nonspecific to a language-specific pattern by assessing the differential cerebral activation and its lateralization in the temporal area.…”

“…The following experiment was designed for the infants for whom short experimental periods are preferred. Two sessions were conducted for each subject: (1) one was the across-category condition (session BC) in which the stimuli differed linguistically, and (2) and the other within-category condition (either session AB or CD) in which the differences were not linguistic but evoked small comparable responses (Minagawa-Kawai et al, 2002). The number of AB and CD sessions, as well as the order of the two conditions, was counterbalanced within each age group.…”

Neural specializations for speech and pitch: moving beyond the dichotomies

“…The bulk of information on tonal processing in the brain comes primarily from two tone languages: Mandarin Chinese, which has four contrastive tones, and Thai, which has five (for reviews, see Gandour (1998Gandour ( , 2006a). Similar arguments in support of domain-specificity could be made for those languages in which duration is used to signal phonemic oppositions in vowel length (Gandour et al 2002a,b;Minagawa-Kawai et al 2002;Nenonen et al 2003). However, cross-language studies of temporal processing do not provide a comparable window for adjudicating between cue-and domain-specificity, because both temporal and language processes are generally considered to be mediated primarily by neural mechanisms in the left hemisphere.…”