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

Katherine (Katie) E Travis^1,2,3*Melissa Scala⁴Virginia A. Marchman⁵Hua Wu⁵Cory K Dodson⁵Lisa Bruckert⁵Molly F Lazarus^2,3Rocio Velasco Poblaciones⁵Kristen Yeom⁴Heidi M Feldman⁴

• ¹Weill Cornell Medicine, Cornell University, New York, United States
• ²Weill Cornell Medicine, New York, United States
• ³Burke Neurological Institute, White Plains, United States
• ⁴Stanford University School of Medicine, Stanford, United States
• ⁵Stanford University, Stanford, United States

Objective: Early speech experiences are presumed to contribute to the development of brain structures involved in processing speech. Previous research has been limited to correlational studies. Here, we conducted a randomized trial with neonates born preterm to determine whether increased exposure to maternal speech during NICU hospitalization is causally linked to structural white matter maturation. Study Design: We enrolled 46 neonates born preterm (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. The C-group did not hear recorded speech. At near-term-equivalent age, we obtained two high-angular resolution diffusion MRI (scan 1: b=700, scan 2: b=1500) and 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). We hypothesized that neonates randomized to the T-group would show evidence for increased maturation within the arcuate, indexed as decreased MD and increased FA and R1, compared to neonates in the C-group. Results: Groups were equivalent on medical and demographic variables. Linear mixed models demonstrated that compared to the C-group, the T-group demonstrated significantly lower MD in the left (scan 1: β=-0.11, Marginal R2=0.27; scan 2: β=-0.12, Marginal R2=0.33) but not right arcuate (scan 1: β=-0.06, Marginal R2=0.09; scan 2: β=-0.03, Marginal R2=0.01). The T-group also demonstrated significantly higher FA (scan 1 β=0.02, Marginal R2=0.20; scan 2: β=0.03, Marginal R2=0.31) and R1 (β=0.02, Marginal R2=0.39) in the left but not right arcuate. Conclusions: Preterm neonates with increased maternal speech exposure showed more mature left arcuate microstructure, supporting a causal role of exposure to speech in brain development. Enhancing speech exposure in the NICU may benefit preterm children’s language outcomes.