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SmartyBrainsHigh-IQ kids navigatenotable neural shifts

The road to exceptional intelligence ispaved with dramatic neural alterations, anew brain-imaging study finds.

Critical parts of the brain’s outer layer, orcortex, thicken more rapidly during child-hood and thin more drastically during ado-lescence in individuals with extremely highIQ scores compared with peers of averageor moderately above-average intelligence,say neuroscientist Philip Shaw of theNational Institute of Mental Health inBethesda, Md., and his colleagues.

The scientists propose that distinctivebrain growth in superior-IQ youth reflectsprolonged development of neural circuitsthat contribute to reasoning, planning, andother facets of analytical thinking.

“Cortical thickness at any one age tellsyou next to nothing about intelligence,”Shaw says. “What’s important is that corti-cal development occurs differently inextremely clever kids, possibly as a resultof particularly efficient sculpting of thebrain.”

The report appears in the March 30Nature.

The researchers used a magnetic reso-nance imaging scanner to track brainchanges in 307 children and teenagersdeemed free of psychiatric or neurologicaldisorders. Most volunteers submitted totwo or more brain scans at intervals aver-aging 2 years. Participants also completeda verbal-and-nonverbal IQ test upon enter-ing the study as children or teenagers.

Earlier research had indicated that IQscores don’t change much over time, so itwasn’t necessary to administer intelligencetests more than once, Shaw says.

The sample was divided into threegroups: 91 youngsters with “superior” IQscores of 121 to 149, 101 with “high” scoresof 109 to 120, and 115 with “average” scoresof 83 to 108. Each group yielded about 200brain scans.

The researchers used a computer pro-gram to analyze average patterns of corti-cal development, from age 7 to 18, in eachgroup.

To Shaw’s surprise, the 7-year-olds withthe highest IQ scores displayed slightlythinner cortices than their peers did. How-ever, the superior-IQ children then expe-rienced particularly rapid cortical thick-ening, which peaked at age 11 to 12. Thesame children’s cortices thinned dramat-ically thereafter.

In average-IQ kids, cortical thicknesspeaked at age 8 and then declined, but to alesser extent than was observed amongsuperior-IQ kids.

High-IQ youngsters displayed a pat-tern of brain development more closelyresembling that of average-IQ peers thanthat of the superior-IQ group. The threegroups ended up with about the same cor-tical thickness.

The most prominent cortical changes,especially in superior-IQ children, occurredin the prefrontal cortex, an area alreadyimplicated in analytical thinking. It’s notknown what cell processes mediate child-hood thickening and thinning of corticaltissue, Shaw notes.

Although IQ measures a narrow set ofanalytical abilities, the new findingshighlight how neural development cul-tivates intelligence, remarks psycholo-gist Elena Grigorenko of Yale Univer-sity. “Children are not born ‘clever’ or‘not clever,’” she says. “Cognitive func-tioning is related to the changing dynam-ics of a complex cascade of brain-matu-ration processes.”

Kids in Shaw’s study who came from thewealthiest families tended to have the supe-rior IQ scores, Grigorenko notes. This raisesthe possibility that environmental factors,from diet to social activities, stimulate thepattern of brain development exhibited bysuperior-IQ kids.

Psychologist Richard Passingham ofthe University of Oxford in Englandagrees but notes that past studies have

shown that genes also substantially influ-ence brain structure and individual dif-ferences in general intelligence (SN:2/8/03, p. 92). —B. BOWER

XXL from TooFew Zs?Skimping on sleep mightcause obesity, diabetes

Widespread sleep deprivation could partlyexplain the current epidemics of both obe-sity and diabetes, emerging data suggest.

Too little sleep may contribute to long-term health problems by changing the con-centrations of hormones that controlappetite, increasing food intake, and dis-rupting the biological clock, according toEve Van Cauter of the University of Chicago.

Van Cauter and other researchers dis-cussed possible links between sleep depri-vation, expanding waistlines, and obesity-related problems this week in Washington,D.C., at a meeting titled A Scientific Work-shop on Sleep Loss and Obesity: Interact-ing Epidemics.

Researchers have observed that peoplewho sleep less than 7 to 8 hours a night haveelevated rates of obesity and diabetes. Inlate 2004, Karine Spiegel of the Free Uni-versity of Brussels in Belgium and VanCauter conducted experiments in healthymen showing that forced sleep restrictionfor 2 days increased appetite and triggeredchanges in the appetite-related hormonesghrelin and leptin (SN: 4/2/05, p. 216). Theobserved ghrelin elevation and leptin sup-pression may have encouraged food intake,Spiegel says.

Before that pivotal study, tests had demon-strated that obesity could disrupt sleep, butfew experiments had investigated whetherlack of sleep could contribute to obesity.

Preliminary results close in on an inde-pendent relationship between sleep loss

THICKHEADED Colored areas of these brain maps highlight regions, mostly locatedtoward the front of the brain, where superior-IQ children developed especially thick corticaltissue by about age 12, compared with average-IQ kids.

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