mardi 24 avril 2012

L'aventure ultime?

"The other major hit from ENIGMA—which analyzed more than 21,000 people—was a chromosome 12q14 polymorphism that associates with greater intracranial volume and brain size. Found near the 3’ untranslated region of HMGA2, a protein important for stem cell renewal, this SNP seems to influence not just brain size but also function. “By having a single switch from a T to C, overall brain size was boosted about 0.5 percent—and if you had two C alleles, it would go up by 1 percent,” Thompson told Alzforum. C carriers also had higher IQ scores, by about 1.3 points per allele. A SNP near HGM2A also came up as a top hit in an independent search for genes associated with infant head circumference, also reported this week in Nature Genetics. Greater head growth during the first year or life has been linked to higher childhood IQ (see Gale et al., 2006)."
http://www.alzforum.org/new/detail.asp?id=3128

The paper by Gale 2006:

Pediatrics. 2006 Oct;118(4):1486-92.

The influence of head growth in fetal life, infancy, and childhood on intelligence at the ages of 4 and 8 years.

Gale CR, O'Callaghan FJ, Bredow M, Martyn CN; Avon Longitudinal Study of Parents and Children Study Team.

Source

Medical Research Council Epidemiology Resource Centre, University of Southampton, Southampton General Hospital, Southampton SO16 6YD, United Kingdom. crg@mrc.soton.ac.uk

Abstract

OBJECTIVE:

We investigated the effects of head growth prenatally, during infancy, and during later periods of development on cognitive function at the ages of 4 and 8 years.

METHODS:

We studied 633 term-born children from the Avon Longitudinal Study of Parents and Children cohort whose head circumference was measured at birth and at regular intervals thereafter. Their cognitive function was assessed with the Wechsler Preschool and Primary Scale of Intelligence at the age of 4 years and with the Wechsler Intelligence Scale for Children at the age of 8 years. Linear regression analysis was used to calculate postnatal head growth between successive time points, conditional on previous size, and to examine the relationship between head growth during different periods of development and later IQ.

RESULTS:

When the influence of head growth was distinguished for different periods, only prenatal growth and growth during infancy were associated with subsequent IQ. At 4 years, after adjustment for parental characteristics, full-scale IQ increased an average of 2.41 points for each 1-SD increase in head circumference at birth and 1.97 points for each 1-SD increase in head growth during infancy, conditional on head size at birth. At 8 years, head circumference at birth was no longer associated with IQ, but head growth during infancy remained a significant predictor, with full-scale IQ increasing an average of 1.56 points for each 1-SD increase in growth.

CONCLUSION:

The brain volume a child achieves by the age of 1 year helps determine later intelligence. Growth in brain volume after infancy may not compensate for poorer earlier growth.