Quantitative susceptibility mapping of striatum in children and adults, and its association with working memory performance.

Quantitative susceptibility mapping (QSM) is a magnetic resonance imaging (MRI) technique in which the magnetic susceptibility characteristic of molecular and cellular components, including iron and myelin, is quantified. Rapid iron accumulation in subcortical nuclei and myelination of the white matter tracts are two important developmental processes that contribute to cognitive functions. Both also contribute to the magnetic susceptibility of the brain tissues. Here, we used the QSM as indirect measures of iron in subcortical nuclei and myelin in caudo-frontal white matter pathways. We included two groups of participants; 21 children aged 6-7years and 25 adults aged 21-40years. All subjects also performed tests estimating their visuo-spatial working memory capacity. Adults had higher magnetic susceptibility in all subcortical nuclei, compared to children. The magnetic susceptibility of these nuclei highly correlated with their previously reported iron content. Moreover, working memory performance correlated significantly with the magnetic susceptibility in caudate nucleus in both children and adults, while the correlation was not significant for gray matter density. QSM of white matter in the caudo-frontal tract also differed between children and adults, but did not correlate with working memory scores. These results indicate that QSM is a feasible technique to measure developmental aspects of changes in the striatum, possibly related to iron content that is relevant to cognition.