EEG Effective Source Projections Are More Bilaterally Symmetric in Infants Than in Adults

Abstract

Although anatomical brain hemispheric asymmetries have been clearly documented in the infant brain, findings concerning functional hemispheric specialization have been inconsistent. The present report aims to assess whether bilaterally symmetric synchronous activity between the two hemispheres is a characteristic of the infant brain. To asses cortical bilateral synchronicity, we used decomposition by independent component analysis (ICA) of high-density electroencephalographic (EEG) data collected in an auditory passive oddball paradigm. Decompositions of concatenated 64-channel EEG data epochs from each of 34 typically developing 6-month-old infants and from 18 healthy young adults participating in the same passive auditory oddball protocol were compared to characterize differences in functional brain organization between early life and adulthood. Our results show that infant EEG decompositions comprised a larger number of independent component (IC) effective source processes compatible with a cortical origin and having bilaterally near-symmetric scalp projections (13.8% of the infant data ICs presented a bilateral pattern vs. 4.3% of the adult data ICs). These IC projections could be modeled as the sum of potentials volume-conducted to the scalp from synchronous locally coherent field activities in corresponding left and right cortical source areas. To conclude, in this paradigm, source-resolved infant brain EEG exhibited more bilateral synchronicity than EEG produced by the adult brain, supporting the hypothesis that more strongly unilateral and likely more functionally specialized unihemispheric cortical field activities are concomitants of brain maturation.

Automatic classification of ICA components from infant EEG using MARA

“…For example, we know that infant alpha activity projected onto central scalp electrodes is present only in later stages of infant development, presumably accompanying advances in motor skills ( Cuevas et al, 2014 ), although the sources of these scalp activations are yet to be identified. Further, at the source level, infant EEG is often more bilaterally symmetrical than adults ( Piazza et al, 2020 ), although strong topographical asymmetry or localisation to a specific topographical point can be a good indication of artifactual source components ( Chaumon et al, 2015 ). This evidence highlights that infant EEG source components do contain topographically distinct properties to those of typical adult EEG.…”

Magnetoencephalography can reveal deep brain network activities linked to memory processes

“…Their localization can be estimated with an equivalent current dipole. In some cases, the SOBI components may correspond to a bilateral activation of homologous brain regions that can be modeled by symmetric dipoles (Bénar et al, 2021; Piazza et al, 2020). We assumed the latter for the SOBI-MEG, representing a bilateral activation of the mesial network.…”

Impact of Early Rhythmic Training on Language Acquisition and Electrophysiological Functioning Underlying Auditory Processing: Feasibility and Preliminary Findings in Typically Developing Infants

“…The electrophysiological functioning underlying auditory processing was explored by means of a non-speech multi-feature paradigm (extensively described previously [ 6 , 13 , 14 , 15 , 47 ]). In this paradigm, pairs of complex tones with an interstimulus interval (ISI) of 70 ms were presented.…”