The auditory brain responses ware different between stuttering and non-stuttering people in all ages

What is it about?

Left/right activation patters (functional lateralization) of the brain is known to be different between people who stutter and who do not stutter. However, it could be due to the long-standing experience of stuttering. This research systematically investigated the functional lateralization of the auditory brain areas from preschoolers to adults, and found a group difference in all age groups. The measurement method used in the research was functional near infrared spectroscopy (fNIRS), which measures the blood concentration in the surface brain from the scalp surface non-invasively using infrared lasers. The blood concentration changes in the brain serve as an index of brain activation levels. Stimulation was changes of either sound (phoneme) or tone (pitch, or prosody) of words pseudo-randomly replacing a repeatedly presented word to both ears. Brain responses were averaged synchronously to the two kinds of stimuli, and peak response amplitudes were statistically compared for the detection of functional lateralization. The results show that none of the people who stutter showed left-dominant (left-greater) lateralization to the sound (phoneme) change relative to tone (pitch) change, in contrast to people who do not stutter, the majority of whom showed a left-dominant pattern in all age groups.

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Why is it important?

It is found that the functional lateralizaiton of the auditory area of the brain to word stimulation is disrupted since very young childhood in those who stutter. This implies that the functional development of the auditory linguistic functions does not proceed normally with developmental stuttering. Although stuttering is primarily speech-motor disorder, this study demonstrated that the disfunction of the brain is not limited to the speech-motor domain but also extends to the auditory-linguistic domain since young childhood.

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