Longitudinal study of functional brain networks for processing infant directed and adult directed speech during the first year

Abstract

In most cultures infant directed speech (IDS) is used to communicate with young children. The main role IDS plays in parent-child interactions appears to change over time from conveying emotion to facilitating language acquisition. There is EEG evidence for the discrimination of IDS form adult directed speech (ADS) at birth, however, less is known about the development of brain networks responsible for differentially processing IDS and ADS. The current study compared topological characteristics of functional brain networks obtained from 49 healthy infants at the age of 0, 6, and 9 months listening to the same fairy tale presented by the same speaker in IDS and ADS speech. Brain connectivity was assessed by the phase lag synchronization index in 6 frequency bands (delta, theta, low alpha, high alpha, beta, gamma). The topology of the large scale network organization was quantified using minimum spanning tree graphs, separately for each band. The delta band cortical networks organization was found to be significantly more hierarchical and had a more cost-efficient organization during listening to ID compared to listening to AD. This network organization changes with age as nodes over the frontal cortex become more central within the network. The general picture emerging from the results is that with development the speech processing network becomes more integrated and its focus is shifting towards the left hemisphere. Our results suggest that ID speech specific differences in network topology are related to changes in the role of IDS during the first year of life. Highlights- Multiple stages of maturation are reflected by different EEG bands, occurring in parallel, but with different timing. - Networks processing infant directed speech changes during the first year of life reflecting the change in the role infant directed speech plays in development. - Speech processing networks are shifting towards the left hemisphere with age. - Longitudinal study of speech perception using functional networks on a large sample