“Cortical white matter increases from childhood (~9 years) to adolescence (~14 years), most notably in the frontal and parietal cortices. Cortical grey matter development peaks at ~12 years of age in the frontal and parietal cortices, and 17 years in the temporal lobes (with the superior temporal cortex being last to mature) for women and they have reached full maturity at age 16-17. For men, they become fully mature at age 18. In terms of grey matter loss, the sensory and motor regions mature first, followed by other cortical regions. Human brain maturation continues to around 20 to 25 years of age.”
That says nothing about what human brain maturation means and to what extend that happens to be a coherent concept.