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The human brain age 7-11 years: a volumetric analysis based on magnetic resonance images
V S Caviness1, D N Kennedy, C Richelme
1Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, USA.
Insights
Child brain development shows significant sex differences in growth patterns. Female brains reach adult volumes earlier in some areas, while male brains may undergo later regression and different white matter development.
Area of Science:
- Neuroscience
- Developmental Biology
- Human Anatomy
Background:
- Childhood brain development is a critical period for establishing adult neural architecture.
- Understanding sex-based differences in brain growth is crucial for identifying developmental trajectories.
Purpose of the Study:
- To investigate sex differences in brain volumetric development in children aged 7-11 years.
- To compare the scaling patterns of brain structures from childhood to adulthood between males and females.
Main Methods:
- Volumetric magnetic resonance imaging (MRI)-based morphometry was used.
- The brains of 30 normal children (15 males, 15 females) aged 7-11 years were analyzed.
Main Results:
- Female brains are 93% of male brain volume at this age.
- Most structures scale uniformly, but caudate, hippocampus, and pallidum are disproportionately larger in females; amygdala is smaller.
- Cerebellum reaches adult volume in females, while forebrain gray matter in males exceeds adult volumes and may regress.
Conclusions:
- Childhood brain development exhibits sexually dimorphic patterns of growth and regression.
- These patterns suggest distinct trajectories for male and female brain maturation.
- Abnormal regulation of these developmental patterns may be linked to neurological disorders.
Abstract:
Volumetric magnetic resonance image (MRI)-based morphometry was performed on the brains of 30 normal children (15 males and 15 males) with a mean age of 9 years (range 7-11 years). This age range lies in a late but critical phase of brain growth where not volumetric increment will be small but when the details of brain circuity are being fine-tuned to support the operations of the adult brain. The brain at this age is 95% the volume of the adult brain. The brain of the female child is 93% the volume of the male child. For more than 95% of brain structures, the volumetric differences in male and female child brain are uniformly scaled to the volume difference of the total brain in the two sexes. Exceptions to this pattern of uniform scaling are the caudate, hippocampus and pallidum, which are disproportionately larger in female than male child brain, and the amygdala, which is disproportionately smaller in the female child brain. The patterns of uniform scaling are generally sustained during the final volumetric increment in overall brain size between age 7-11 and adulthood. There are exceptions to this uniform scaling of child to adult brain, and certain of these exceptions are sexually dimorphic. Thus, with respect to major brain regions, the cerebellum in the female but not the male child is already at adult volume while the brainstem in both sexes must enlarge more than the brain as a whole. The collective subcortical gray matter structures of the forebrain of the female child are already at their adult volumes. The volumes of these same structures in the male child, by contrast, are greater than their adult volumes and, by implication, must regress in volume before adulthood. The volume of the central white matter, on the other hand, is disproportionately smaller in female than male child brain with respect to the adult volumes of cerebral central white matter. By implication, relative volumetric increase of cerebral central white matter by adulthood must be greater in the female than male brain. The juxtaposed progressive and regressive patterns of growth of brain structures implied by these observations in the human brain have a soundly established precedent in the developing rhesus brain. There is emerging evidence that sexually dimorphic abnormal regulation of these terminal patterns of brain development are associated with gravely disabling human disorders of obscure etiology.