title: Developmental Trajectories in Primary Schoolchildren Using n-Back Task.
abstract: BACKGROUND
  Neuropsychological instruments to assess cognitive trajectories during childhood in epidemiological studies are needed. This would improve neurodevelopment characterization in order to identify its potential determinants. We aimed to study whether repeated measures of n-back, a working memory task, detect developmental trajectories in schoolchildren during a 1-year follow-up.
  
  
  METHODS
  We administered the n-back task to 2897 healthy children aged 7-11 years old from 39 schools in Barcelona (Spain). The task consisted of 2 levels of complexity or loads (2- and 3-back) and 2 different stimuli (numbers and words). Participants performed the task four times from January 2012 to March 2013. To study the trajectories during the follow-up, we performed linear mixed-effects models including school, individual and age as random effects.
  
  
  RESULTS
  We observed improvements related to age in n-back outcomes d', HRT and accuracy, as well as reduced cognitive growth at older ages in d' and HRT. Greater improvements in performance were observed at younger ages, in 2-back, in verbal rather than numerical stimuli and in girls compared to boys. Boys responded faster at baseline, while girls showed increased growth in 2-back numbers. Children with ADHD (Attention Deficit and Hyperactivity Disorder) symptoms (15% of boys and 6% of girls) had a lower working memory at baseline, but they showed similar cognitive growth trajectories in numbers variants of the task, as compared to children without ADHD symptoms. However, the age-related improvement in response speed was not observed in children with ADHD symptoms.
  
  
  CONCLUSIONS
  Changes in n-back outcomes reflected developmental trajectories in 1-year follow-up. The present results suggest that the repeated administration of this task can be used to study the factors that may alter the cognitive development during childhood.
authors.affiliation: ISGlobal, Centre for Research in Environmental EpidemiologyBarcelona, Spain; Department of Experimental and Health Sciences, Universitat Pompeu FabraBarcelona, Spain; CIBER Epidemiología y Salud PúblicaBarcelona, Spain; Hospital del Mar Medical Research InstituteBarcelona, Spain.
authors.forename: Mónica
authors.initials: M
authors.lastname: López-Vicente
authors.affiliation: ISGlobal, Centre for Research in Environmental EpidemiologyBarcelona, Spain; Department of Experimental and Health Sciences, Universitat Pompeu FabraBarcelona, Spain; CIBER Epidemiología y Salud PúblicaBarcelona, Spain; Department of Genes and Environment, Division of Epidemiology, Norwegian Institute of Public HealthOslo, Norway.
authors.forename: Joan
authors.initials: J
authors.lastname: Forns
authors.affiliation: ISGlobal, Centre for Research in Environmental EpidemiologyBarcelona, Spain; Department of Experimental and Health Sciences, Universitat Pompeu FabraBarcelona, Spain; Learning Disabilities Unit (UTAE), Neuropediatrics Department, Hospital Sant Joan de Déu, Universitat de BarcelonaBarcelona, Spain.
authors.forename: Elisabet
authors.initials: E
authors.lastname: Suades-González
authors.affiliation: ISGlobal, Centre for Research in Environmental EpidemiologyBarcelona, Spain; Department of Experimental and Health Sciences, Universitat Pompeu FabraBarcelona, Spain; CIBER Epidemiología y Salud PúblicaBarcelona, Spain.
authors.forename: Mikel
authors.initials: M
authors.lastname: Esnaola
authors.affiliation: ISGlobal, Centre for Research in Environmental EpidemiologyBarcelona, Spain; Department of Experimental and Health Sciences, Universitat Pompeu FabraBarcelona, Spain; CIBER Epidemiología y Salud PúblicaBarcelona, Spain.
authors.forename: Raquel
authors.initials: R
authors.lastname: García-Esteban
authors.affiliation: ISGlobal, Centre for Research in Environmental EpidemiologyBarcelona, Spain; Department of Experimental and Health Sciences, Universitat Pompeu FabraBarcelona, Spain; CIBER Epidemiología y Salud PúblicaBarcelona, Spain.
authors.forename: Mar
authors.initials: M
authors.lastname: Álvarez-Pedrerol
authors.affiliation: ISGlobal, Centre for Research in Environmental EpidemiologyBarcelona, Spain; Department of Experimental and Health Sciences, Universitat Pompeu FabraBarcelona, Spain; CIBER Epidemiología y Salud PúblicaBarcelona, Spain; Hospital del Mar Medical Research InstituteBarcelona, Spain; Environmental Health Department, Harvard T.H. Chan School of Public HealthBoston, MA, USA.
authors.forename: Jordi
authors.initials: J
authors.lastname: Júlvez
authors.affiliation: Center for Brain and Cognition, Department of Technology, Universitat Pompeu Fabra Barcelona, Spain.
authors.forename: Miguel
authors.initials: M
authors.lastname: Burgaleta
authors.affiliation: Center for Brain and Cognition, Department of Technology, Universitat Pompeu Fabra Barcelona, Spain.
authors.forename: Núria
authors.initials: N
authors.lastname: Sebastián-Gallés
authors.affiliation: ISGlobal, Centre for Research in Environmental EpidemiologyBarcelona, Spain; Department of Experimental and Health Sciences, Universitat Pompeu FabraBarcelona, Spain; CIBER Epidemiología y Salud PúblicaBarcelona, Spain; Hospital del Mar Medical Research InstituteBarcelona, Spain.
authors.forename: Jordi
authors.initials: J
authors.lastname: Sunyer
keywords: follow-up; longitudinal study; n-back; neurodevelopment; population study; schoolchildren; working memory