Scientists at Stanford University have found that the density of one type of receptor in the brain is linked to the structure of areas important for math and reading skills in children. The work was published in the journal Nature Communications.
The receptors in question are NMDA receptors - proteins on the surface of nerve cells that respond to glutamate, the brain's main "excitatory" chemical messenger. These receptors play a key role in plasticity - the ability of connections between neurons to change under the influence of experience.
The study involved 991 children aged 7-14 without developmental peculiarities. First, data from 760 children (mean age 9.7 years, 275 girls) from the Healthy Brain Network project were analyzed, then the results were checked in an independent sample of 231 children (mean age 9.2 years, 98 girls) from Stanford studies. The children underwent standard tests of counting, problem solving, word reading and reading comprehension, as well as MRI brain scanning.
The researchers compared gray matter volume in 218 brain areas with math and reading performance, and then compared these data with an atlas of the distribution of 19 neurotransmitter systems built from PET scans of adults. Of the 19 systems, only NMDA receptors showed a consistent link in both groups of children: areas with higher gray matter volume associated with academic success were more often rich in these receptors. The link was moderate - the distribution of NMDA receptors explained 8 to 20% of the differences between brain areas.
Other systems, including dopamine, acetylcholine, serotonin and GABA, produced weaker or inconsistent results. For example, the link with acetylcholine and histamine for math appeared in only one sample.
For math, the link with NMDA receptors spanned several brain networks, including the default mode network (active when a person is not focused on a task), the salience network (responsible for highlighting important stimuli) and the high-level visual perception network. For reading, the consistent link was limited to a network involved in recognizing written words.
Math and reading scores were strongly correlated - that is, they were statistically related, which in itself does not prove causality. An additional analysis showed that the link with NMDA receptors mainly reflects brain structure common to both skills. The authors suggest that glutamate signaling may be a shared biological basis of learning abilities, but manifests through different systems depending on the skill.
An important limitation: the scientists did not measure NMDA receptors or glutamate in the children themselves. The receptor maps were taken from earlier scans of 1,200 healthy adults, and children's brains change as they develop, so adult maps may not fully reflect the pediatric picture. In addition, the analysis compared patterns across brain areas rather than receptors in individual children, so it cannot be said that children with more NMDA receptors are better at math or reading. The study was cross-sectional and included only typically developing children aged 7-14, so it does not show whether glutamate signaling influences the development of these skills.