Cerebral Asymmetry and Cognitive Development in Children: A Magnetic Resonance Imaging Study

Phonemic awareness, the ability to abstract and manipulate auditory symbols, is a distinguishing human characteristic. Neurobiological specializations in the left hemisphere and cultural exposure to language interact to shape development of this ability. Modern imaging techniques now permit investigation of the interaction of these forces. In this initial cross-sectional study, we found evidence for a shift from neurobiological to cultural regulation. In young children, aged 5 to 9, anatomical asymmetry of the auditory association cortex predicted phonemic awareness. In older children, the relationship disappeared, as all children became skilled readers. The findings suggest that children with different patterns of cognitive strengths and weaknesses may have different spatiotemporal patterns of cortical development.