Phonemic manipulation in Japanese: an fMRI study.

Phonological awareness is the ability to manipulate abstract phonological representations of language and is crucial to the process of learning to read. The neural substrates underlying this appear to be modality-independent at least in alphabetic languages. Japanese language has different orthographic "kana" system, in which each "kana" character strictly corresponds to a syllable. To investigate the neural substrates underlying phonological manipulation of the Japanese language, functional magnetic resonance imaging (fMRI) was used. Neuroimaging data were obtained from adult healthy volunteers during auditory and visual vowel exchange tasks, identical except for the modality of stimuli presentation: a voice and Japanese "kana" characters. Cerebellar vermis was activated by vowel exchange tasks of both modalities. The posterior parts of the superior temporal sulcus (STS) were active during the auditory tasks, suggesting that phonological representations of auditory stimuli are manipulated in this area. These findings are consistent with the previous studies with alphabetic languages. In contrast, the intraparietal sulci, which has been implicated for visuospatial tasks, was active during the visual tasks. This modality-dependent activation may indicate that the simple orthographic rule of the Japanese allows an alternate visual strategy to conduct the phonological awareness task, bypassing manipulation of phonological representation.