Abstract
To understand the evolution of human behavior and brain, it is fundamental to determine how brain development of humans differs from that of chimpanzees (Pan troglodytes). The area of particular interest for human evolution is the prefrontal area, which mediates high-order behaviors such as, working memory, attention, planning, decision making, or social behaviors. We studied the development of the gray matter (GM) and white matter (WM) in the frontal area of 1 male and 3 female chimpanzees, at the ages of 2 months to 7 years old. MRI images were acquired using T1-weighted, gradient echo imaging with a 0.2T MR imager. We examined GM and WM volumes in the prefrontal area, the frontal area, and the whole brain using FSL software. The prefrontal and the frontal areas were defined as all portions anterior to the corpus callosum and the anterior commissure respectively, in a plane perpendicular to the line connecting the anterior and posterior commissures. The results revealed that (1) growth spurts of whole brain and the frontal area were seen during the 2 years after birth, (2) after this period, GM volume decreased in both the prefrontal and frontal area, (3) whereas WM volume increased throughout childhood at a slow rate, especially in the prefrontal area, (4) the prefrontal WM volume has not yet maturated to an adult level at seven years old, as in humans. Our findings may uncover key information on human brain development and its relation to functional and evolutionary milestones. [J Physiol Sci. 2008;58 Suppl:S143]
