A study from the Advanced Baby Imaging Lab at Brown University took brain MRI's of 133 babies ranging in age from 10 months to four years. They did it while they were sleeping, in case you're also wondering.
Controlling for gestation times and socioeconomic status, the babies who were exclusively breasted had 20-30% more white matter than those fed exclusively formula. Babies who received a combination ranked in between. White matter is the tissue that contains long nerve fibers and helps different parts of the brain communicate with each other.
The authors bolstered their imaging data with a set of basic cognitive tests on the older children. Those tests found increased language performance, visual reception, and motor control performance in the breastfed group.
This study adds to a substantial body of evidence linking breastfeeding to brain development and other benefits. That is why we here at Pariday know that breastfeeding pain relief is not just a "nice-to-have." If it helps mothers get though breastfeeding challenges, it not only helps their children, it helps our whole society.
For more info on the study please see: http://news.brown.edu/pressreleases/2013/06/breastfeeding