Human infant crying has been researched as a non-invasive tool for assessing neurophysiological states at an early developmental stage. Little is known about the acoustic features of spontaneous cries in preterm infants, although their pain-induced cries are at a higher fundamental frequency ( F ₀ ) before term-equivalent age. In this study, we investigated the effects of gestational age, body size at recording and intrauterine growth retardation (IUGR) on the F ₀ of spontaneous cries in healthy preterm and full-term infants at term-equivalent age. We found that shorter gestational age was significantly associated with higher F ₀ , although neither smaller body size at recording nor IUGR was related to increased F ₀ in preterm infants. These findings suggest that the increased F ₀ of spontaneous cries is not caused by their smaller body size, but instead might be caused by more complicated neurophysiological states owing to their different intrauterine and extrauterine experiences.

This study investigated whether lower vagal function in preterm infants is associated with increased fundamental frequency (F₀; frequency of vocal fold vibration) of their spontaneous cries. We assessed respiratory sinus arrhythmia (RSA) during quiet sleep as a measure of vagal function, and its relationship with the F₀ of spontaneous cries in healthy preterm and term infants at term‐equivalent age. The results showed that preterm infants have significantly lower RSA, and higher overall F₀ than term infants. Moreover, lower RSA was associated with higher overall F₀ in preterm infants, whereas higher RSA was positively associated with mean and maximum F₀, and a larger F₀ range in term infants. These results suggest that individual differences in vagal function may be associated with the F₀ of spontaneous cries via modulation of vocal fold tension in infants at an early developmental stage. © 2016 The Authors. Developmental Psychobiology Published by Wiley Periodicals, Inc. Dev Psychobiol 58:724–733, 2016.

There is growing evidence that preterm children are at an increased risk of poor executive functioning, which underlies behavioural and attention problems. Previous studies have suggested that early cognitive flexibility is a possible predictor of later executive function; however, how it develops in infancy and relates to the later neurobehavioural outcomes is still unclear in the preterm population. Here, we conducted a longitudinal study to investigate oculomotor response shifting in 27 preterm and 25 term infants at 12 months and its relationship with general cognitive development and effortful control, which is a temperamental aspect closely associated with executive function, at 18 months. We found that moderate to late preterm and term infants significantly inhibited previously rewarded look responses, while very preterm infants did not show significant inhibition of perseverative looking at 12 months. Moreover, lower inhibition of perseverative looking was significantly associated with lower general cognitive development and attentional shifting at 18 months. These findings suggest that the early atypical patterns of oculomotor response shifting may be a behavioural marker for predicting a higher risk of negative neurobehavioural outcomes, including attention-related problems in preterm children.

Infants’ social touch with caregivers has been considered a means of regulating infant physiological and emotional state. In non-human mammals, such regulatory function also facilitates infant exploration and social behavior. However, the types of social touch in human mother–infant interaction that contribute to specific behavioral responses toward people and objects remain unclear. Using a pre- and post-task design, this study investigated the effects of social touch during mother–infant interactions on infants’ subsequent preferential looking at social stimuli, social engagement with strangers, and object exploration. Between tasks, mothers and infants spent the time playing in one of two conditions, More Physical Contact or Less Physical Contact. We found that infants in the More Physical Contact Condition showed a greater decrease in evasive behavior with the stranger and enhanced object exploration than those in the Less Physical Contact Condition. Conversely, social touch did not affect infants’ preferential looking at static social images. Among the types of social touch, the frequency of affectionate touch reduced evasive behavior to the stranger and facilitated object exploration. These results suggest that social touch, especially affectionate touch, during mother–infant interactions, assist in the modulation of infants’ evasive behaviors toward people and object exploration.

Executive function (EF) consists of explicit emotion regulation (EER) and cognitive control (CC). Childhood EER in particular predicts mental and physical health in adulthood. Identifying factors affecting EER development has implications for lifelong physical and mental health. Gut microbiota (GM) has attracted attention as a potential biomarker for risk of physical and mental problems in adulthood. Furthermore, GM is related to brain function/structure, which plays a crucial role in emotional processing. However, little is known about how GM compositions are associated with the development of emotion regulation in early childhood. Therefore, in this study, we examined 257 children aged 3–4 to investigate links between GM and risk to EF. EF was measured using the Mother-Reported Behavior Rating Inventory of Executive Function–Preschool version. GM composition (alpha/beta diversity and genus abundance) was evaluated using 16S rRNA gene sequencing and compared between EF-risk and non-risk groups. Our results show that children with EER-risk (an index of inhibitory self-control) had a higher abundance of the genera Actinomyces and Sutterella. Although we have not established a direct link between GM and CC risk, our findings indicate that GM of preschoolers is closely associated with emotional processing and that EERrisk children have more inflammation-related bacteria.