Rapid maturation of voice and linguistic processing systems in preschool children: A near-infrared spectroscopic study

To better understand how voice and linguistic processing systems develop during the preschool years, changes in cerebral oxygenation were measured bilaterally from temporal areas using multi-channel near-infrared spectroscopy (NIRS). NIRS was recorded while children listened to their mothers' voice (MV), an unfamiliar female voice (UV) and environmental sound (ES) stimuli. Twenty typical children (aged 3-6 years) were divided into younger (Y) (n = 10, male = 5; aged 3-4.5 years) and older (O) (n = 10, male = 5; aged 4.5-6 years) groups. In the Y group, while MV stimuli significantly activated anterior temporal areas with a right predominance compared to ES stimuli, they significantly activated left mid-temporal areas compared to UV stimuli. These temporal activations were significantly higher in the Y group compared to the O group. Furthermore, only the O group exhibited significant habituation and gender differences in the left mid-temporal area during MV perception. These findings suggest that the right voice-related and the left language-related temporal areas already exist in the Y group, and that MV stimuli modulate these areas differently in the two age groups. Therefore, we conclude that a mother's voice plays an important role in the maturation of the voice and linguistic processing systems, particularly during the first half of the preschool-aged period. This role may decrease during the latter half of the preschool-aged period due to rapid development of these systems as children age.