ROI NODDI analysis
NDI
A complementary NODDI analysis was performed to better understand the microstructural alterations underlying the FBA metrics changes observed from the 33rd week GA to term-equivalent age and, in particular, in relation to the music intervention.The ROIs showing a significantly different longitudinal FBA metrics evolution between PTM and PTC groups were selected and warped to the subject space, using the warps derived from the FBA pipeline. The warped ROIs were used to calculate NODDI metrics in the subjects’ ODI and NDI maps. Multivariate repeated measures ANCOVA, controlling for GA at MRI time-point 1, delta of the GA at MRI between the two time-points and sex was conducted to determine statistically significant differences between PTM and PTC groups on the NODDI metrics from the 33rd week GA to term-equivalent age (time*group interaction) in the selected brain ROIs, using IBM SPSS Statistics version 25 (IBM Corp., Armonk, N.Y., USA). Given that our data lack sphericity (Mauchly’s sphericity test p < 0.05), we present the p-value results using Greenhouse-Geisser correction. Since the socio-economic parental status score (SES) was marginally significantly different between groups, we present additionally the results of a sensitivity analysis, where we include SES in our model as a covariate. GA at birth was not a significant predictor for any of the dependent variables, which is why it was not included as a covariate in the final analysis.