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Abstract:
Much research has been directed at identifying the
neuroanatomic systems governing working memory, with less attention
to the origins of individual differences in working memory skills.
The importance of understanding individual differences is
highlighted by the presence of working memory deficits in diverse
neurodevelopmental disorders (schizophrenia, attention deficit
disorder, dyslexia). Further, increases in working memory
contribute to intellectual growth during childhood. In this study
of 18 children (ages 7-12) we wished to determine (1) whether
variation in frontal lobe brain chemistry, determined from proton
magnetic spectroscopy, is related to performance on a working
memory task in children, and (2) whether developmental instability
(DI; the imprecise expression of the genetic plan for development
due to several known genetic and environmental effects) underlies
phenotypic variation in brain chemistry. The Two Back test assessed
working memory. A composite measure of DI was created from measures
of minor physical anomalies, fluctuating asymmetry of body
characteristics, and fluctuating asymmetry of dermatoglyphic
features. A STEAM pulse sequence, including water suppression, was
used to sample a 2x2x3 cm voxel in right frontal white matter
(TE=30ms, TR=2000ms, 128 averages). Water resonances were removed
using HLSVD filtering. Time-domain fitting of gaussian lineshapes
to NAA, creatine, and choline was carried out using VARPRO. Higher
levels of DI strongly predicted lower MRS levels of creatine and
choline, while MRS levels of creatine and NAA positively correlated
with working memory skills. Working memory skills thus seem related
to frontal lobe energy metabolism, which in turn is related to
DI.
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