Maturation of preterm newborn brains: a fMRI-DTI study of auditory processing of linguistic stimuli and white matter development

To evaluate brain development longitudinally in premature infants without abnormalities as compared to healthy full-term newborns, we assessed fMRI brain activity patterns in response to linguistic stimuli and white matter structural development focusing on language-related fibres. A total sample of 29 preterm newborns and 26 at term control newborns underwent both fMRI and DTI. Griffiths test was performed at 6 months of corrected age to assess development. Auditory fMRI data were analysed in 17 preterm newborns at three time points [34, 41 and 44 weeks of post menstrual age (wPMA)] and in 15 controls, at term. Analysis showed a distinctive pattern of cortical activation in preterm newborns up to 29 wPMA moving from early prevalent left temporal and supramarginal area activation in the preterm period, to a bilateral temporal and frontoopercular activation in the at term equivalent period and to a more fine-grained left pattern of activity at 44 wPMA. At term controls showed instead greater bilateral posterior thalamic activation. The different pattern of brain activity associated to preterm newborns mirrors their white matter maturation delay in peripheral regions of the fibres and thalamo-cortical radiations in subcortical areas of both hemispheres, pointing to different transient thalamo-cortical development due to prematurity. Evidence for functional thalamic activation and more mature subcortical tracts, including thalamic radiations, may represent the substantial gap between preterm and at term infants. The transition between bilateral temporal activations at term age and leftward activations at 44 weeks of PMA is correlated to better neuropsychological results in Griffiths test.