Editors' ChoiceBrain Development

Prenatal Conditions Shape Cognition

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Science Translational Medicine  01 Aug 2012:
Vol. 4, Issue 145, pp. 145ec136
DOI: 10.1126/scitranslmed.3004663

It is crucial to protect the prenatal environment so that the earliest stages of brain development proceed smoothly. However, it remains unclear whether conditions during these early events influence later brain maturation in the postnatal period. Some insights have come from observation of children who experienced insults to their prenatal environments such as malnutrition or radiation exposure. Now, Raznahan et al. explore whether variations in normal birth weight are associated with detectable differences in brain development and cognitive function that persist beyond childhood.

Population-wide research has suggested that birth weight provides a reliable index of optimal brain development in the womb. Indeed, even low-birth-weight babies who are born full term have an increased risk of poor cognitive functioning and psychiatric conditions, including schizophrenia and affective or anxiety disorders. The authors analyzed more than 1000 structural magnetic resonance imaging (MRI) brain scans performed at 2-year intervals in human subjects between the ages of 3 to 30 years. To link variations in prenatal environment to brain outcomes independent of genetic, gestational, and maternal differences, these researchers associated birth weight and brain outcome in a subset of monozygotic twin pairs. As postnatal outcomes of interest, Raznahan et al. measured cognitive ability indexed by full-scale, verbal, and performance intelligence quotient as well as global brain volumes and focused on the relationship between birth weight and postnatal anatomy of the cerebral cortex. Greater birth weight within the normal range resulted in a sustained and generalized increase in brain volume, which in the cortical sheet is driven specifically by altered surface area rather than cortical thickness. Surface area was maximally sensitive to birth-weight variation within cortical regions that have been implicated in the biology of several mental disorders, the risk for which is modified by normative variations in birth weight. Thus, these results link subtle differences in prenatal growth with protracted surface area alterations that preferentially affect later-maturing associative cortices important for higher cognition.

Although birth-weight differences between monozygotic twins are a useful measure for environmentally driven variations in growth in utero, they are likely to encompass diverse patterns of divergent growth between twins that vary in their timing and underlying physiological mechanism. In addition, the capacity of variations in birth weight to predict later brain anatomy may be influenced by other factors, such as head size at birth. Nevertheless, mapping the sensitivity of postnatal human brain development to prenatal influences has significant implications for how life in the womb can shape the adult brain.

A. Raznahan et al., Prenatal growth in humans and postnatal brain maturation into late adolescence. Proc. Natl. Acad. Sci. U.S.A. 109, 11366–11371 (2012). [PubMed]

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