Listening to Mom in the Neonatal Intensive Care Unit: A randomized trial of increased maternal speech exposure on white matter connectivity in infants born preterm.

Background: Early speech experiences have been proposed to contribute to the development of brain structures involved in processing spoken language. However, previous research has been limited to correlational studies. Here, we conducted an RCT with preterm neonates to determine whether increased exposure to maternal speech during NICU hospitalization is causally linked to structural white matter maturation. Methods: We enrolled 46 preterm neonates (24-31 weeks gestational age). Participants were randomly assigned to receive increased (T: n=21) or routine (C: n=25) exposure to mother's speech. The T-group heard 10-minute audio recordings of their mothers reading a children's story two times/hour between 10pm-6am, increasing speech exposure by 2.67 hours/day. At near-term-equivalent age, we obtained two high-angular resolution diffusion MRI (scan 1 bvalue=700, scan 2 bvalue=1500) and quantitative T1 relaxometry scans. We assessed mean diffusivity (MD), pre-registered primary outcome ( NCT02847689 ), of the left and right arcuate fasciculus, tracts implicated in language processing. Secondary outcomes included fractional anisotropy (FA) and R1 (1/T1). Findings: T- and C-groups were equivalent on medical and demographic variables. Compared to the C- group, the T-group demonstrated significantly lower MD in the left (scan 1: mean difference Interpretation: Preterm neonates who experienced increased exposure to maternal speech during hospitalization demonstrated more mature microstructure of the left arcuate. Findings provide evidence for a causal link between speech experiences and brain development. Increasing speech exposure in the NICU may benefit preterm children. Research in Context Panel: