The corpus callosum, the largest fiber tract connecting the cerebral hemispheres, is the principal path transferring information between hemispheres. The typical development of the corpus callosum is significant for the development of cognitive function, and agenesis of the corpus callosum, characterized by developmental absence of the corpus callosum is closely related to neurological and psychotic disorders. For the reason that school age is a neurobiological critical period for the development of brain and cognitive function, this present study explored the typical growing law of corpus callosum morphology during school age in China and the relationship between the development of corpus callosum morphology and the development of cognitive function. Three studys had been included in this project. Study 1 examined the reliability of corpus callosum morphology measurement, which was precondition for scientific research involving corpus callosum morphology. In study 2, the development trajectories of multiple corpus callosum morphology measurement indexes during school age were built in China. In study 3, the relationships between the development of cognitive function and the development of corpus callosum morphology in school age were investigated.
In the first study, for examining the test-retest reliability of corpus callosum morphology measuring, fifty-four adults (18 ~ 36 years old) from the 3R-Brain Project were scanned four times in two different 3T magnetic resonance scaners from two different sites. The results showed that for most of corpus callosum morphology measurement indexes, the test-retest reliability was almost perfect (ICC > 0.8). However, for the thickness of the two ends of the corpus callosum, the test-retest reliability was lower. The test-retest reliability intra-scaner is heigher than the test-retest reliability inter-scaners.
In the second study, based on the accelerated longitudinal design, 391 Chinese children in school-age (6 ~ 18 years old) were traced. The Generalized Additive Mixed Models (GAMM) was applying to draw the developmental trajectories of corpus callosum morphology. The results showed that the development of corpus callosum morphology was dynamic in school-age children. Pubertal development of the corpus callosum was again accelerated. The boys’ developmental trajectories of corpus callosum morphology were different than girls’. After 16 years old, the corpus callosum area begins to decline in girls. The developmental trajectories of different corpus callosum regions were different from each other. The development rate of the genu and splenium of the corpus callosum decreased with age. However, the development rate of the middle region is relatively stable. Introducing the total intracranial volume (eTIV) as additional covariate, the developmental trajectories of corpus callosum morphology were still significant. The developmental trajectories of relative measuring of corpus callosum morphology were significant, which meant the development of corpus callosum was over-proportional.
In study 3, the Wechsler Intelligence Scale for Children-Fourth Edition (WISC-IV) was used to assess children’s cognitive functions. The GAMM was applying to exploring the relationships between corpus callosum morphology and cognitive functions. The time-varying effect model was applying to exploring whether the relationships between corpus callosum morphology and cognitive functions varied with age. The results showed that the development of corpus callosum morphology could explain the development of cognitive functions. And the relationships were moderated by sex and corpus callosum region. The relationships between corpus callosum morphology and cognitive functions varied with age.
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