High-density electroencephalography developmental neurophysiological trajectories

Longitudinal high-density cortical auditory event-related potentials and speech-sound discrimination in the first two years of life in extremely and very preterm infants without developmental disorders

Maturation of the auditory system in early childhood significantly influences the development of language-related perceptual and cognitive abilities. This study aims to provide insights into the neurophysiological changes underlying auditory processing and speech-sound discrimination in the first two years of life. We conducted a study using high-density electroencephalography (EEG) to longitudinally record cortical auditory event-related potentials (CAEP) in response to synthesized syllable sounds with pitch/duration change in a cohort of 79 extremely and very preterm-born infants without developmental disorders. EEG were recorded at 6 timepoints from term to 24 months corrected age, using a pseudorandom oddball paradigm. We found that the infant-P1 component of CAEP showed decreasing latency with age and more focalized cortical source stabilizing in the left primary auditory cortex by 6 months. By 6 months, a negative infant-N1 component emerged, its amplitude increasing with age and source localization showing increasing distribution over the left temporal, parietal and frontal lobes. Mismatch responses demonstrated significant differences in auditory discrimination capabilities starting from 6 months, indicating the infants' ability to detect phonetic differences. There was no correlation between infant-P1 latency, infant-P1 amplitude or mismatch response at term age and gestational age. This study suggests that cortical sound detection occurs very early and is not significantly influenced by the extent of prematurity but rather by corrected age. Early sound detection is followed by cortical sound content processing from about 6 months, with gradual organization along the cortical auditory dorsal stream and mirror neuron system in the first two years of life. Auditory discrimination of speech sounds also significantly changes from around 6 months of age.

High-density neonatal electroencephalography provides biomarkers for developmental trajectories

This commentary is on the original article by Ventura et al. on pages 1395–1407 of this issue.

Multiscale entropy as a metric of brain maturation in a large cohort of typically developing children born preterm using longitudinal high-density EEG in the first two years of life

Objective.We aimed to analyze whether complexity of brain electrical activity (EEG) measured by multiscale entropy (MSE) increases with brain maturation during the first two years of life. We also aimed to investigate whether this complexity shows regional differences across the brain, and whether changes in complexity are influenced by extrauterine life experience duration.Approach.We measured MSE of EEG signals recorded longitudinally using a high-density setup (64 or 128 electrodes) in 84 typically developing infants born preterm (<32 weeks' gestation) from term age to two years. We analyzed the complexity index and maximum value of MSE over increasing age, across brain regions, and in function of extrauterine life duration, and used correlation matrices as a metric of functional connectivity of the cerebral cortex.Main results.We found an increase of strong inter-channel correlation of MSE (R > 0.8) with increasing age. Regional analysis showed significantly increased MSE between 3 and 24 months of corrected age in the posterior and middle regions with respect to the anterior region. We found a weak relationship (adjusted R²= 0.135) between MSE and extrauterine life duration.Significance.These findings suggest that brain functional connectivity increases with maturation during the first two years of life. EEG complexity shows regional differences with earlier maturation of the visual cortex and brain regions involved in joint attention than of regions involved in cognitive analysis, abstract thought, and social behavior regulation. Finally, our MSE analysis suggested only a weak influence of early extrauterine life experiences (prior to term age) on EEG complexity.