Post-adolescent developmental changes in cortical complexity
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RESEARCH
Open Access
Post-adolescent developmental changes in cortical complexity Anca-Larisa Sandu1,2*, Edouard Izard3, Karsten Specht2,4, Harald Beneventi2, Arvid Lundervold3,5 and Martin Ystad3
Abstract Background: Post-adolescence is known to be a period of general maturation and development in the human brain. In brain imaging, volumetric and morphologic cortical grey-matter changes can easily be assessed, but the analysis of cortical complexity seems to have been broadly neglected for this age interval. Methods: Magnetic resonance imaging (MRI) was used to acquire structural brain images. The study involved 17 adolescents (mean age 14.1 ± 0.27, 11 girls) who were compared with 14 young adults (mean age 24.24 ± 2.76, 7 women) for measures of brain complexity (fractal dimension - FD), grey matter (GM) volume and surface-area of cortical ribbon. FD was calculated using box-counting and Minkowski-Bouligand methods; FD and GM volume were measured for the whole brain, each hemisphere and lobes: frontal, occipital, parietal and temporal. Results: The results show that the adults have a lower cortical complexity than the adolescents, which was significant for whole brain, left and right hemisphere, frontal and parietal lobes for both genders; and only for males in left temporal lobe. The GM volume was smaller in men than in boys for almost all measurements, and smaller in women than in girls just for right parietal lobe. A significant Pearson correlation was found between FD and GM volume for whole brain and each hemisphere in both genders. The decrease of the GM surface-area was significant in post-adolescence for males, not for females. Conclusions: During post-adolescence there are common changes in cortical complexity in the same regions for both genders, but there are also gender specific changes in some cortical areas. The sex differences from different cortical measurements (FD, GM volume and surface-area of cortical ribbon) could suggest a maturation delay in specific brain regions for each gender in relation to the other and might be explained through the functional role of the corresponding regions reflected in gender difference of developed abilities. Keywords: Grey matter, Fractal dimension, Development, Dimorphism, Magnetic resonance imaging
Background Morphological changes in the brain occur throughout life span [1,2], involving grey matter (GM) and white matter (WM) and affecting both brain structure and shape complexity [3-6]. From post-mortem studies it is known that cellular changes, as regionally variable synaptic pruning [7] together with increased myelination of intra-cortical fibres [8] continue during childhood and adolescence, and that this may underlie structural changes observable at MRI resolution [1]. The total GM volume peaks during * Correspondence: [email protected] 1 Aberdeen Biomedical Imaging Centre, Lilian Sutton Building, University of Aberdeen, Foresterhill, AB25 2ZD Aberdeen, UK 2 Department of Biological and Medical Psychology, University of Bergen, Jonas Lies
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