In order to quantify human brain development in vivo, high resolution magnetic resonance images of 158 normal subjects from infancy to young adulthood were studied (age range 3 months-30 years, 71 males, 87 females). Data were analysed using algorithms based on voxel-based morphometry (VBM) (an objective whole brain processing technique) to generate global volume measures of whole brain, grey matter (GM) and white matter (GM). Gender-specific development of WM and GM volumes is characterised using a piecewise polynomial growth curve model to account for the non-linear nature of human brain development, implemented using Markov chain Monte Carlo simulation. The statistical method employed in this study proved to be successful and robust in the characterisation of brain development. The resulting growth curve parameter estimates lead to the following observations: total brain volume is demonstrated to undergo an initial rapid spurt. The total GM volume peaks during childhood and decreases thereafter, whereas total WM volume increases up to young adulthood. Relative to brain size, GM decreases and WM increases markedly over this age range in a non-linear manner, resulting in an increasing WM-to-GM ratio over much of the observed age range. In addition, significant gender differences are found. In general, brain volume and total white and grey matter volume are larger in males than in females, with a time-dependent difference over the age range studied. Over part of the observed age range females tend to have more GM volume relative to brain size and lower WM-to-GM ratio than males. The presented findings should be taken into account when investigating physiological and pathological changes during brain development.
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