Hemispheric lateralization of speech perception in infancy and childhood: A systematic review

Abstract

Past neuroimaging research has shown left hemisphere dominance for the neural processing of speech in the mature adult brain. How this hemispheric asymmetry develops however, remains largely unknown. It is unclear whether this left lateralization is observed at birth, or whether this functional specialization develops with neural maturation and experience perceiving speech. This systematic review examined evidence from 13 papers that used a variety of neuroimaging modalities to investigate the neural processing of speech stimuli in infants and children. The two primary goals of this review were to identify at what age left hemisphere dominance emerges and to characterize the developmental trajectory of hemispheric lateralization from infancy to childhood. Of the papers that met inclusionary criteria, 5 used electroencephalography (EEG), 4 used functional magnetic resonance imaging (fMRI), 3 used functional near-infrared spectroscopy (fNIRS), and 1 used magnetoencephalography (MEG). The papers were divided into three age groups: birth to 12 months, 1 to 8 years, and 8 to 18 years. Of the infant papers, significant variability in stimuli, methods, and findings made it difficult to determine whether the neural processes for speech perception are left lateralized in the first year, as many papers show left lateralization for both speech and nonspeech stimuli. Among the papers investigating lateralization among children, there was some evidence suggesting bilateral activation at younger ages with a shift to left hemisphere dominance as children develop. Two papers investigated lateralization in children with autism and concluded that, perhaps, it is more likely for children with autism to show atypical right lateralization.