title: Lower Working Memory Performance in Overweight and Obese Adolescents Is Mediated by White Matter Microstructure.
abstract: OBJECTIVE
  Elevated body mass index (BMI) is associated with deficits in working memory, reduced gray matter volume in frontal and parietal lobes, as well as changes in white matter (WM) microstructure. The current study examined whether BMI was related to working memory performance and blood oxygen level dependent (BOLD) activity, as well as WM microstructure during adolescence.
  
  
  METHODS
  Linear regressions with BMI and (1) verbal working memory BOLD signal, (2) spatial working memory BOLD signal, and (3) fractional anisotropy (FA), a measure of WM microstructure, were conducted in a sample of 152 healthy adolescents ranging in BMI.
  
  
  RESULTS
  BMI was inversely related to IQ and verbal and spatial working memory accuracy; however, there was no significant relationship between BMI and BOLD response for either verbal or spatial working memory. Furthermore, BMI was negatively correlated with FA in the left superior longitudinal fasciculus (SLF) and left inferior longitudinal fasciculus (ILF). ILF FA and IQ significantly mediated the relationship between BMI and verbal working memory performance, whereas SLF FA, but not IQ, significantly mediated the relationship between BMI and accuracy of both verbal and spatial working memory.
  
  
  CONCLUSIONS
  These findings indicate that higher BMI is associated with decreased FA in WM fibers connecting brain regions that support working memory, and that WM microstructural deficits may underlie inferior working memory performance in youth with higher BMI. Of interest, BMI did not show the same relationship with working memory BOLD activity, which may indicate that changes in brain structure precede changes in function.
authors.affiliation: 1Department of Behavioral Neuroscience,Oregon Health & Science University,Portland,Oregon.
authors.forename: Gabriela
authors.initials: G
authors.lastname: Alarcón
authors.affiliation: 1Department of Behavioral Neuroscience,Oregon Health & Science University,Portland,Oregon.
authors.forename: Siddharth
authors.initials: S
authors.lastname: Ray
authors.affiliation: 1Department of Behavioral Neuroscience,Oregon Health & Science University,Portland,Oregon.
authors.forename: Bonnie J
authors.initials: BJ
authors.lastname: Nagel
mesh_terms: D000293:Adolescent; D015992:Body Mass Index; D002648:Child; D056324:Diffusion Tensor Imaging; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008569:Memory Disorders / Q000209:etiology* / Q000473:pathology*; D008570:Memory, Short-Term / Q000502:physiology*; D009765:Obesity / Q000150:complications*; D050177:Overweight / Q000150:complications*; D010100:Oxygen / Q000097:blood; D012044:Regression Analysis; D066127:White Matter / Q000000981:diagnostic imaging / Q000473:pathology
chemical_list: D010100:Oxygen
keywords: Adolescent development; Body mass index; Diffusion tensor imaging; Executive function; Magnetic resonance imaging; Multimodal imaging