Auditory structural connectivity in preterm and healthy term infants during the first postnatal year

Abstract

Assessing language development in the first postnatal year is difficult, as receptive and expressive skills are rudimentary. Although outward manifestations of change are limited, the auditory language system is thought to undergo critical development at this age, as the foundations are laid for the rapid onset of spoken language in the second and third years. We recruited 11 infants, 7 healthy controls (gestational age = 40.69 ± 0.56; range from 40 to 41.43) and preterm babies (gestational age = 28.04 ± 0.95; range from 27.43 to 29.43) who underwent a Magnetic Resonance Imaging study during the first postnatal year (age at scan = 194.18 ± 97.98). We assessed white matter tracts using diffusion-weighted magnetic resonance imaging with probabilistic tractography. Fractional anisotropy was found to be largely mature even at one month, although there was a little further increase during the first postnatal year in both the acoustic radiation and the direct brainstem-Heschl's pathway.

Neonatal Frequency-Following Responses: A Methodological Framework for Clinical Applications

“…In addition to confirming previous findings regarding the similarity of the FFR between newborns and adults in terms of neural encoding of the voice pitch, results revealed that the ability of the newborn brain to encode spectrotemporal fine structure is weaker than that of adults, especially for higher sound frequencies. 48 In line with the previous literature, their results suggest that the neural encoding of the temporal fine structure is not yet fully mature at birth, but would require sound, language exposure, and time 47 57 58 to further develop to the level of maturity observed in adults. Overall, newborn studies demonstrate that the FFR is a brain response whose maturity would be affected by not only the maturation of brain tissues but also by the existence of certain postnatal stimulation received by the infant.…”

“…In this sense, it is important to highlight that after birth, the newborn's auditory system is still immature and is not yet able to encode high spectral components of speech. 46 47 Therefore, the typical stimuli commonly used for the study of the neural encoding of the characteristics of speech sounds in adults, when used in newborns, only permit the optimal study of neural encoding of the fundamental frequency of the stimulus and its low-frequency harmonics. This provides a measure to study whether the newborn brain is capable of encoding inflections in the pitch contour of the voice, which are one of the main speech features in tonal languages such as Mandarin.…”

“… 53 On the other hand, spectral representation of higher harmonics is still developing in term infants and increases significantly with increasing age 53 through at least 10 months of age. 54 The mandatory delay of exposure to high frequencies until birth caused by the high-frequency filter of the mother's womb 55 56 along with the increasing myelination of the auditory system during the first year of life 47 may explain the lower sensitivity to the frequencies located at the upper end of the spectrum during the first years of life. Thus, the high frequencies of the first formants of the /da/ stimulus (i.e., 688 and 1,214 Hz for the first and second formants, respectively) could impede the encoding of the sound fine structure in neonates.…”

Inferring the infant pain experience: a translational fMRI-based signature study

“…Although caution is advised when translating and interpreting adult signatures in the immature brain 37 , there is considerable evidence to support the validity of this approach. Core structural features of the mature adult brain are developed in term-aged infants 38,39 . We see functional responses 40–43 , connectivity patterns, and resting state activity 44,45 exhibit similar features to adult brain activity.…”

Bouncing the network: A dynamical systems model of auditory–vestibular interactions underlying infants’ perception of musical rhythm

“…However, as suggested by work on movement and music in infants, the perception of musical rhythm in infancy likely involves interactions between developing auditory, motor, and vestibular systems (Gerry et al, 2010; Phillips‐Silver & Trainor, 2005)—systems that we hypothesize are initially weakly and diffusely coupled in infancy (Sheya & Smith, 2010). Already, many white‐matter tracts in the auditory system have developed by early infancy (Zubiaurre‐Elorza et al, 2018), possibly indicating that developing auditory, motor, and vestibular systems are structurally linked in early infancy. To account for auditory–vestibular interactions, we expand Tichko and Large (2019)’s model, a multi‐frequency network of non‐linear oscillators with Hebbian plasticity, to include an additional motor network, allowing the model to receive vestibular inputs, such as infant bouncing.…”