Functional lateralization during phonological word processing in children who stutter - Measured by near-infrared spectroscopy

Near-infrared spectroscopic measurement of cerebral hemodynamics was used to investigate cerebral dominance during auditory language processing in preschool and school-age children who stutter. Analysis-synthesized Japanese words (/itta/ and /itte/) and intonation contrasts (/itta/ and /itta?/) were used for stimuli. The baseline block contained only /itta/, whereas the contrast block consisted of either the minimal pair or intonation pair, with the contrast words presented in random order at equal probabilities. To analyze cerebral lateralization, we calculated a laterality index (LI) from the peaks of the left and right total Hb responses for each contrast block, compared to the preceding baseline block in the auditory area. The results showed that there were no significant differences in LI between the minimal pair and intonation conditions in children who stutter. Within-subject analysis showed no subject with a significant leftward shift of LI in the minimal pair condition relative to the intonation condition. These results indicate that the cerebral dominance in processing heard speech may be in disarray in children who stutter.