3.2. Gray and white matters
Stronger growth of gray matter (GM) compared to white matter (WM) was observed during the early postnatal period and the first year of life in both sexes (Knickmeyer, R.C. et al. 2008; Gilmore JH et al., 2007),. It was described that male compared to female infants had about 10.2% more GM volume, 6.4% more WM volume, and 7.8% more subcortical GM volume (Gilmore JH et al., 2007; Dean DC et al., 2018). This suggests that larger cortical GM can be considered as the main contributor to a larger brain volume in males (Reiss AL. et al, 1996). In contrast, in prematurely born infants, Benavides et al. have shown greater GM volume in females but greater WM volume in males (Benavides A et al., 2019). The data recorded in neonates suggest that brain WM and GM maturation is a continuous process and does not stop in infancy but continues at a different rate in boys and girls.
The growth of the brain GM is concurrent with the development of several cognitive and motor functions. However, abnormalities in early brain development have been implicated in neurodevelopmental disorders, such as overgrowth of GM volumes in children who are at high risk of autism (Hazlett HC et al., 2019), and increased cortical GM volume in male infants at high genetic risk of schizophrenia (Gilmore JH et al., 2010).