[1] Univ London, Ctr Brain & Cognit Dev Birkbeck, London, England
[2] UCL, Med Phys & Bioengn, London WC1E 6BT, England
[3] Keneba MRC Unit, Int Nutr Grp, Serrekunda, Gambia
[4] London Sch Hyg & Trop Med, MRC Int Nutr Grp, London, England
[5] Univ Cambridge, MRC Human Nutr Res, Cambridge, England