New paper from PhD student Dennis Dimond: here.
Communication throughout the brain is important for proper brain function and cognition. Different areas of the brain communicate by sending signals along axons that act like roads connecting distant brain areas. Much like how roads come together to form highways, axons in the brain group together into fiber bundles when connecting brain areas that are far apart. Fiber bundles undergo structural changes during brain development that are believed to increase the effectiveness of communication throughout the brain, and lead to maturation of cognitive skills like reading and math. It’s unclear, however, how the size of fiber bundles and density of axons in these bundles change during important periods of development like early childhood.
In this study, we investigated changes in fiber bundle size and density of axons in major fiber bundles in the brain during early childhood. To do this, we used magnetic resonance imaging (MRI) to measure fiber bundle structure in 73 girls who were scanned at ages 4-7, and again one-year later at ages 5-8. We then calculated and compared the rates of change in fiber bundle size and axon density across 20 fiber bundles in the brain.
We found that both fiber bundle size and density of axons increased with age in most fiber bundles, though increases in size were more substantial and observed in more fiber bundles than increases in axon density. We also found that rates of change varied across fiber bundles, with faster growth in fiber bundles important in motor skills, and slower growth in bundles important in complex cognitive functions like decision making. These findings are in line with what we know about maturation of brain functions; motor skills develop in childhood-adolescence, while decision making skills continue to develop into adulthood. Overall, our findings suggest that both fiber bundle size and axon density increase during early childhood. These changes may be important in the development of cognitive and behavioral skills.