hide
Free keywords:
Lateralization; Language; Preschool children; Longitudinal; Cortical thickness
Abstract:
The two hemispheres of the human brain differ in their anatomy and function. This asymmetric anatomy and function can already be observed in the early stages of life and has been shown to further change with age. The development of the brain’s asymmetry has also been observed with respect to language, as one of the most lateralized cognitive functions, favoring the left hemisphere in the healthy adult brain. However, it still remains unclear how language-related structural asymmetry and its developmental changes are related to language abilities. We collected longitudinal structural magnetic resonance imaging data in children when they were 5 and 6 years old and assessed their language abilities when they were 5, 6, as well as 7 years old. Specifically, language abilities were assessed by a standardized language test, measuring general sentence comprehension abilities of children. Children were presented with a picture matching task, in which the child is auditorily presented wi th a sentence and three pictures from which the child has to choose the correct picture matching the presented sentence. Structural asymmetry was quantified by the laterality index of the cortical thickness of those language related regions frequently reported in previous studies (i.e., frontal and temporoparietal regions). Our results showed substantial language performance changes across development (i.e., between ages 5 and 7), with only subtle changes of the brain’s cortical thickness asymmetry (i.e., between ages 5 and 6). Crucially however, changes of cortical thickness asymmetry in the inferior frontal cortex between the ages of 5 and 6 were associated with changes of sentence comprehension abilities, suggesting an improvement in language abilities to be influenced by larger cortical thinning in the left compared to the right inferior frontal gyrus. Further, the asymmetry of the inferior frontal cortex of the younger brain (i.e., at age 5 and 6 years) was associated with th e children’s language performance at the age of 7. To our knowledge, this is the first longitudinal study to demonstrate that children’s improvement in sentence comprehension seems to depend on cortical thickness asymmetry changes in the inferior frontal cortex, further highlighting the crucial role of this region in language acquisition.
