Early music intervention enhances cortical GM maturation during early brain development
PREMATURE BIRTH, CORTEX
Based on the observed brain maturational changes occurring from the 33rd week GA to term-equivalent age, we have further evaluated the longitudinal effect of the music intervention on those maturational processes.Our results suggest that an early postnatal music intervention, given to very preterm infants during NICU stay, enhances the maturation of certain cortical GM regions. In particular, it led to a FC increase in the left orbito-frontal cortex, left temporal pole, left insula, right middle temporal gyrus and right precuneus/posterior cingulate gyrus. This FC increase possibly reflects an increase in the number of dendrites and intra-cortical myelination. Indeed, the third trimester of pregnancy is marked by an important activity-dependent neural plasticity. The thalamocortical neurons bridge the cortical circuitry with sensory periphery, allowing sensory-driven activity to modulate neuronal connections. Providing an external organized auditory stimulus in the form of music to very preterm infants during this critical period, has thus led to an enhanced cortical maturation of regions important mostly for social-emotional processing.The orbito-frontal cortex, temporal pole and insula constitute what is known as the insulo-orbito-temporopolar complex of the paralimbic brain, sharing histologic and functional similarities (These findings are in line with our previous study, showing that a similar early postnatal music intervention during NICU stay led to a significant increase of FA in the uncinate fasciculus, a WM bundle connecting the orbito-frontal cortex to the temporal pole, in very preterm infants at term-equivalent age (It is important to highlight that structural alterations affecting the insulo-orbito-temporopolar complex have been further related to the later socio-emotional deficits observed in preterm born infants (The right middle temporal gyrus is part of the auditory association cortex and has been shown to be activated during passive music listening (Regarding the precuneus and the posterior cingulate cortex, these regions have been shown (together with the auditory cortex) to be functionally activated when musical stimuli elicit emotions (When controlling for socio-economic parental status score (SES) in our additional sensitivity analysis, the longitudinal FC increase remains significantly greater in the music intervention group in comparison to the control group for the same brain regions, except for the precuneus/posterior cingulate gyrus. There is actually a tendency for a greater longitudinal FC increase in this region in the music group in comparison to the control group, but this difference is no longer significant. We can thus consider that for this particular region the variability found between groups diminishes when correcting for SES, which is marginally significantly superior in the music group in comparison to the control group. Previous studies have shown that SES is strongly associated with preterm infant’s later cognitive outcomes, namely at 18–24 months and 5 years of age, although not with brain volumes at term-equivalent age (Gui et al., 2018). Since the precuneus/posterior cingulate gyrus complex is known to have an important role in cognition (Another interesting finding is the laterality effect of the music intervention on the right middle temporal gyrus, the left insulo-orbito-temporopolar complex and the right precuneus/posterior cingulate gyrus. In adults, key acoustic characteristics of melodic and harmonic music have been shown to activate right cortical auditory areas (Altogether, our findings support that an early postnatal music intervention given to very preterm infants during NICU stay may induce the maturation of specific cortical regions undergoing important maturational changes from the 33rd week GA to term-equivalent age and that have been previously shown be affected by premature birth. These cortical regions comprise important paralimbic cortical areas such as the left insulo-orbito-temporopolar complex, the right posterior component of DMN (right precuneus/posterior cingulate gyrus), as well as the right auditory association cortex, what might contribute to mitigate the deficits in behavior and social-emotional cognition observed later on in the preterm population.