Haden, G. P. | bioRxiv Science

bioRxiv2023

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

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

neuroscience↗

bioRxiv2022

Beat processing in newborn infants cannot be explained by statistical learning based on transition probabilities

Newborn infants have been shown to extract temporal regularities from sound sequences, both in the form of learning regular sequential properties, and extracting periodicity in the input, commonly referred to as a beat. However, these two types of regularities are often indistinguishable in isochronous sequences, as both statistical learning and beat perception can be elicited by the regular alternation of accented and unaccented sounds. Here, we manipulated the isochrony of sound sequences in order to disentangle statistical learning from beat perception in sleeping newborn infants in an EEG experiment, as previously done in adults and macaque monkeys. We used a binary accented sequence that induces a beat when presented with isochronous timing, but not when presented with randomly jittered timing. We compared mismatch responses to infrequent deviants falling on either accented or unaccented (i.e., odd and even) positions. Results showed a clear difference between metrical positions in the isochronous sequence, but not in the equivalent jittered sequence. This suggests that beat processing is present in newborns. However, the current paradigm did not show effects of statistical learning, despite previous evidence for this ability in newborns. These results show that statistical learning does not explain beat processing in newborn infants. Research highlightsSleeping newborns process musical beat. Transition probabilities are not enough to explain beat perception in newborn infants. No evidence of statistical learning (based on transition probabilities) without isochronous stimulation in newborns. Results converge with previous evidence on beat perception of newborn infants.

neuroscience↗