Brains develop differently in smartest kids

Brains develop differently in smartest kids

By Robert Lee Hotz
Los Angeles Times

Smart children have a different rhythm in their heads, a seesaw pattern of growth that lags years behind other young people, say government scientists who mapped the brains of hundreds of children.

Seeking a link between neural anatomy and mental ability, researchers at the National Institutes of Mental Health (NIMH) and McGill University in Montreal discovered it where they least expected — not in sheer brain size or special structures, but in the patterns of childhood growth.

Brain development in children with the highest IQs peaked four years later than among average children, the researchers reported Wednesday in the journal Nature.

"Smart children really do develop differently, and here is the first physical evidence of that," said neuroscientist Paul Thompson of the University of California, Los Angeles. "You'd think they'd develop faster and earlier than normal kids. The surprise is they don't," said the expert on imaging and brain development.

Philip Shaw at the NIMH child-psychiatry branch and his colleagues periodically scanned the brains of 307 healthy children from age 5 through adolescence to age 19.

To monitor the living brains, they employed magnetic resonance imaging. To gauge intelligence, they gave each child standard IQ tests.

When images were analyzed, researchers found distinctive patterns of brain development that differed depending on the child's age and IQ.

In particular, the anatomical scans revealed waves of change in the prefrontal cortex, a thick, wrinkled carpet of cells that shapes memory, attention, perceptual awareness, language, reason and consciousness.

"It's not that brainy children have more gray matter," Shaw said. "The story of intelligence is in the trajectory of brain development. What differs with intelligence is the rate of these changes."

Among average children studied, those with an IQ measuring between 83 and 108, the growth of the cortex peaked at age 8. Among those with high intelligence, those with an IQ between 109 and 120, growth peaked at age 9.

The smartest children, those with IQs between 121 and 145, displayed a pattern of brain growth that peaked at 11 or 12.

The anatomical scans revealed that among the smartest children, the cortex displayed the longest period of growth and most rapid rate of change.

"There is something very dynamic about these brains," said Dr. Judith Rapoport of the NIMH. "What the intelligent children have is a very malleable brain."

No single brain scan could reveal a child's IQ. The patterns revealed themselves across a large group. They are differences measured in fractions of a millimeter of brain tissue that emerge over a decade or more.

"These are tiny changes," Shaw said. "But in brain terms, it is a lot."

It's not known whether such subtle developmental changes in the cortex are caused by the genes inherited from a child's parents, by the biochemical influences of life experience, or by the interplay of both.