Presented at the Neonatal Society 2016 Summer Meeting.
Telford EJ, Anblagan D, Fletcher-Watson S, Cox S, Pataky R, Piyasena C, Sparrow SA, Semple SI, Bastin M, Boardman JP
University of Edinburgh
Background: A general factor (g) of white matter microstructure provides a neural basis of information processing speed and intelligence in adults (1,2). The temporal emergence of g during human development is unknown. Social cognition is one of the first cognitive domains to develop, and it can be evaluated using eye-tracking technology during infancy (3). We tested the hypothesis that white matter microstructure is substantially shared across tracts (g) in the newborn, and explored whether it contributes to the neural substrate of infant social cognition.
Methods: 145 neonates (GA at birth range 23+2 to 41+5 weeks) underwent diffusion MRI (dMRI) at term equivalent age (mean GA 40+5 weeks, range 37+5- 47+1) and eye-tracking assessment 6- 12 months later (median age 7.9 months, IQR 6.8-8.8). dMRI was acquired with 64 diffusionweighted (b=750 s/mm2) single-shot spin-echo echo planar imaging volumes. Probabilistic neighbourhood tractography (PNT)4 was used to generate tract-averaged integrity parameters for 8 major white matter fasciculi: fractional anisotropy (FA), mean diffusivity (MD), axial (λrad) and radial diffusivity (λrad). For each diffusion parameter, values for each of the tracts were entered into a principal component analysis (PCA). Infant eye-tracking in response visual stimuli was used to calculate a social preference score, which is a measure of infant cognition (3). The relationship between dMRI measures of WMI and social cognitive performance was investigated using regression models.
Results: Each of the four PCAs showed a substantial first component. The first unrotated factor
explained the following variances: 48.5% (FA), 54.0% (MD), 36.6 % (λax) and 58.9% (λrad).
All eight tracts showed positive loadings, and factor structures were comparable across each
of the four dMRI measures. Mean between-tract Pearson correlations ranged between 0.60
and 0.76. The figure shows white matter tract segmentations (representative individual
displayed) and the statistics on the lines are the factor loadings of the average FA values per
tract. After controlling for age at MRI and age at eye-tracking, gFA did not correlate with
social cognitive performance p=0.309.
Conclusion: A substantial amount of microstructural variance is shared between major tracts in the newborn brain, which indicates that the general factor of WMI, known to be associated with intelligence in later life, is present during development. Further work is required to determine whether the newborn g of white matter integrity contributes to the development of cognitive processes associated with intelligence (processing speed, attention and habituation); and whether g is modified by adverse perinatal events such as preterm birth.
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1. Penke L et al. Journal of Neuroscience 2010
2. Penke L et al Mol Psych 2012
3. Telford et al J Child. Psychol. Psychiatr 2016
4. Anblagan et al NeuroImage:Clinical 2015