Developmental changes in backbone of brain functional network during the infancy period

Abstract

In a normal development, structure and functions of the infant’s brain change efficiently to enable one’s communication with the external world. However, it is still a mystery that how dominant connections of the brain network called “backbone” change in the infancy period. In this study developmental changes in the backbone of functional brain network are investigated. Therefore, resting state EEG of 15 infants (7 girls, full-term) with no family health problem were recorded at the ages of 6 and 18 months. Subsequently, the brain functional network was estimated from the cleaned EEG using Weighted Phase Lag Index (WPLI) algorithm. The WPLI network was then explored using the graph theory by Minimum Spanning Tree. Parameters of the MST including diameter, betweenness, leaf number, eccentricity, and hierarchy were calculated. Subsequently, a pairwise t-test was performed based on the MST parameters to compare backbone of the brain network between both age groups. Based on the Power Spectral Analysis, four frequency bands including delta, lower alpha, lower beta, and gamma bands were selected, each of them investigated separately. The results showed an increase of eccentricity and diameter, and a reduction in leaf numbers, betweenness and hierarchy (lower complexity) in the functional networks of the frequencies with enhanced power (eg. gamma). In addition, opposite results were observed in the networks related to the frequencies with declined power (eg. delta). Our findings indicate that backbone of the brain functional network changes in a frequency specific manner, and a reverse order follows the changes in oscillatory pattern.