Scientists from King's College London have found that intelligence level in childhood is linked to the pace of brain restructuring in adolescence. The work was published in the journal Developmental Cognitive Neuroscience. The researchers Phoebe Thomson, Philip Shaw and Divyangana Rakesh analyzed data from 10,495 children in the United States who were followed from childhood to mid-adolescence.
In adolescence the brain actively restructures. Gray matter, where neuron cell bodies are located, first grows and then shrinks in the process of "synaptic pruning" - the removal of excess connections between nerve cells. White matter, which works like communication cables between brain regions, strengthens: a protective myelin sheath forms around nerve fibers.
At the start of the study the children took tests on different aspects of intelligence. The scientists divided them into three categories: fluid intelligence (the ability to solve new problems, remember and quickly process information), crystallized intelligence (accumulated knowledge, such as vocabulary and reading comprehension) and matrix reasoning (the ability to find patterns in visual images).
Brain development was tracked using three types of magnetic resonance imaging (MRI). Structural MRI showed the volume, surface area and thickness of gray matter. Diffusion MRI recorded changes in the microstructure of white matter. Resting-state functional MRI recorded how different brain networks interact with each other.
It turned out that children with higher fluid intelligence lost gray matter volume faster. This effect was especially noticeable in the frontal lobe, which is responsible for complex thinking and decision-making. Cortical thickness and other intelligence measures were not statistically significantly linked to changes in gray matter.
Matrix reasoning predicted the pace of white matter maturation. Children with high scores on this test started with higher white matter integrity, but then it grew more slowly and over a more extended period of time. This manifested in several large pathways connecting the frontal lobe with other areas.
Functional connectivity - the synchronization of activity across different brain networks - also depended on early intelligence. In children with low baseline scores, the connection between networks strengthened over time. In more able children, by contrast, the connection between some networks that normally become segregated in adolescence declined faster, for example between auditory processing and cognitive control. In addition, in them the default mode network (active during internal reflection) and attention networks became more strongly separated.
The authors emphasize: the study is observational, it does not prove that high intelligence directly causes these changes. Shared factors are possible, for example genetics or environmental conditions, that influence both mental abilities and brain maturation. In addition, due to incomplete data from the last measurement point, the scientists used mainly linear models, although brain development often proceeds unevenly. Further observations over a wider age range will help refine the picture.