Discussion
CORTEX
In this longitudinal study we have evaluated preterm infants’ brain early structural changes, as well as the effect of an early music intervention in these structural changes occurring from the 33rd week GA to term-equivalent age. For that we used FBA, a recent method that allows to investigate whole-brain fiber-specific micro- and macrostructural changes, complemented with NODDI analysis, in order to better understand the observed microstructural changes related to the music intervention.The major findings from this study are: 1) there is an important longitudinal increase of FD, FDC and especially of FC, in all major cerebral WM fibers bilaterally, as well as in the thalamus, brainstem, cerebellum and cerebellar peduncles, revealing thus important micro- and macroscopic maturation of the WM fiber bundles during this period, suggesting axonal growth and myelination. Interestingly, from all WM fibers, the projection fibers were the ones exhibiting the most prominent maturational changes; 2) in diverse cortical GM regions, there is a significant increase of FC, accompanied by a decrease of FD and FDC, revealing important intracortical maturational changes occurring during this period, characterized by multidirectional complexification as well as intracortical myelination; 3) the music intervention lead to a longitudinal accelerated maturation of specific cortical GM regions, marked by a significantly superior increase of FC in the left insulo-orbito-temporopolar complex, right precuneus/posterior cingulate gyrus and right middle temporal gyrus, accompanied, in addition, of a significantly superior ODI increase in the left temporal pole and left orbito-frontal cortex.