The corpus callosum (CC) is the largest connective pathway in the human brain, linking cerebral hemispheres. There is longstanding debate in the scientific literature whether sex differences are evident in this structure, with many studies indicating the structure is larger in females. However, there are few data pertaining to this issue in infancy, during which time the most rapid developmental changes to the CC occur. In this study, we examined longitudinal brain imaging data collected from 104 infants at ages 6, 12, and 24 months. We identified sex differences in brain-size adjusted CC area and thickness characterized by a steeper rate of growth in males versus females from ages 6–24 months. In contrast to studies of older children and adults, CC size was larger for male compared to female infants. Based on diffusion tensor imaging data, we found that CC thickness is significantly associated with underlying microstructural organization. However, we observed no sex differences in the association between microstructure and thickness, suggesting that the role of factors such as axon density and/or myelination in determining CC size is generally equivalent between sexes. Finally, we found that CC length was negatively associated with nonverbal ability among females.
Bibliographical noteFunding Information:
This research was supported by grants from the National Institutes of Health ( K01-MH101653 , R01-HD055741 , HD055741-S1 , P30-HD03110 ), a student fellowship award from the American Academy of Child and Adolescent Psychiatry , and the National Alliance for Medical Image Computing, funded by the NIH Roadmap for Medical Research ( U54- EB005149 ). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
© 2020 The Authors
- Brain imaging
- Corpus callosum
- Sexual dimorphism