Working memory emerges in infancy and plays a privileged role in subsequent adaptive cognitive development. The neural networks important for the development of working memory during infancy remain unknown. We used diffusion tensor imaging (DTI) and deterministic fiber tracking to characterize the microstructure of white matter fiber bundles hypothesized to support working memory in 12-month-old infants (n= 73). Here we show robust associations between infants' visuospatial working memory performance and microstructural characteristics of widespread white matter. Significant associations were found for white matter tracts that connect brain regions known to support working memory in older children and adults (genu, anterior and superior thalamic radiations, anterior cingulum, arcuate fasciculus, and the temporal-parietal segment). Better working memory scores were associated with higher FA and lower RD values in these selected white matter tracts. These tract-specific brain-behavior relationships accounted for a significant amount of individual variation above and beyond infants' gestational age and developmental level, as measured with the Mullen Scales of Early Learning. Working memory was not associated with global measures of brain volume, as expected, and few associations were found between working memory and control white matter tracts. To our knowledge, this study is among the first demonstrations of brain-behavior associations in infants using quantitative tractography. The ability to characterize subtle individual differences in infant brain development associated with complex cognitive functions holds promise for improving our understanding of normative development, biomarkers of risk, experience-dependent learning and neuro-cognitive periods of developmental plasticity.
Bibliographical noteFunding Information:
This research was supported by the following grants: NIMH Silvio O. Conte Center ( MH064065 ) and Twin ( MH070890 and MH091645 ), NICHD ( HD053000 ), IDDRC ( P30-HD003110 ), and NRSA ( T32 NS007431 ). SJS and JTE were supported by NRSA awards ( T32 HD040127 and 5T32HD007376 , respectively) from NICHD . MS and GG were additionally supported by the National Alliance for Medical Image Computing (NA-MIC) , funded by the NIH ( U54 EB005149 ). In addition, we gratefully acknowledge Dianne Evans, Mary Norton, Bob Hamer, Amanda Lyall, Xiujuan Geng, and Janice Linn for their contributions to this project, and the research assistants involved in testing the infants: Elizabeth Misiti, Kathryn Cochrane, Hillary Langley, Sarah Palmer, Portia Henderson, Molly McGinnis, and Emily Bostwick. We are also deeply grateful to the families of the infants for their willingness to involve their infants, and themselves, in this work.
- Brain development
- Diffusion tensor imaging
- White matter
- Working memory