Roles of culture and COMT Val58Met gene on neural basis of executive function: A comparison between Japanese and American children.

The development of executive functions (EF) is shaped by both genetic and environmental factors, including cultural background. Genetically, variation in the catechol-O-methyltransferase (COMT) gene polymorphism has been linked to EF performance and differential regulation of prefrontal cortex activity. Based on the gene-culture interaction framework, we tested whether culture would moderate the association between the COMT gene and young children's behavioral responses and neural activities during a cognitive-shifting EF task. The children who participated in this study were 5- to 6-year-olds in Japan (n = 44) and in the U.S. (n = 47). The results revealed that U.S.-American children exhibited stronger activations than Japanese children in the right dorsolateral and bilateral prefrontal cortex regions. In addition, the children's genetic disposition and EF performance were marginally moderated by culture, with Val homozygote Japanese children performing better than Met-allele carriers, whereas no such differences were found in U.S.-American children. We have discussed the theoretical and empirical implications of the construction of a more complete understanding of EF development by incorporating both genetic and socio-cultural factors.

Are there sex differences in the development of prefrontal function during early childhood?

Research has demonstrated the possibility of minor sex differences in executive function (EF) development of young children; however, this may be limited to the measurements used in previous studies (questionnaires and cognitive tasks), which tend to be less sensitive to the detection of sex differences. The present study uses brain measures to examine the effect of sex on EF development. In this study, preschool children were given an EF task, and patterns of activation in the lateral prefrontal regions were measured by a functional near-infrared spectroscopy. In Study 1, there were no behavioral differences between girls and boys, though girls showed stronger prefrontal activation than boys. Study 2 was conducted as an attempt to replicate the results, and some of the results were inconsistent with the results in Study 1. Results suggest that sex differences in EF tasks are small, although such differences may exist irrespective of methodology.

Less Is More Activation: The Involvement of the Lateral Prefrontal Regions in a "Less Is More" Task.

The present study examined whether the lateral prefrontal regions played an important role in a less is more (LIM) task in young children. Preschool children were given a LIM task, and neural activation during the task was assessed using a functional near-infrared spectroscopy. Results revealed that children's right ventrolateral prefrontal regions were activated during the task. Specifically, stronger prefrontal activation was shown when children chose a small reward compared to when they selected the other option. Results suggest that the lateral prefrontal regions, the core region of cool EF, contributes to performance in the LIM task.

Socioeconomic disparity in prefrontal development during early childhood.

Socioeconomic status (SES) has a powerful influence on cognitive, social and brain development. Children from low-SES backgrounds show poor executive function (EF). However, it is unclear if there is a SES-dependent disparity in functional brain development. The present study examined whether the SES of preschool children (N = 93) is associated with prefrontal activation during cognitive shifting tasks as measured by near-infrared spectroscopy. Low-SES children did not show activation in lateral prefrontal regions during the tasks, whereas middle- and high-SES children showed prefrontal activations, although no differences were found in terms of behavioural performance. These results suggest that SES can affect the functional development of the prefrontal regions. In this study, we discuss the practical implications of the results.

Neural correlates of delay of gratification choice in young children: Near-infrared spectroscopy studies.

Delay of gratification refers to the ability to forgo a small immediate reward to obtain a larger delayed reward. Cognitive mechanisms underlying the delay of gratification in young children have been examined extensively. However, the neural mechanism of this process is largely unknown. The present study examined whether inferior prefrontal regions play an important role in the delay of gratification choice paradigm in young children. Preschool children were given a choice version of a delay of gratification task, and their neural activation during the task was assessed using near-infrared spectroscopy in cross-sectional (Study 1) and longitudinal designs (Study 2). Results revealed the activation of the right inferior prefrontal regions of children during the task in both studies. Specifically, the inferior prefrontal regions of the children were activated during immediate choices but not during delay choices. This study is the first to demonstrate the neural correlates of the delay of gratification in young children. We discuss how the right inferior prefrontal regions of preschool children are activated during the delay of gratification.

Effect of the COMT Val158Met genotype on lateral prefrontal activations in young children.

Low executive function (EF) during early childhood is a major risk factor for developmental delay, academic failure, and social withdrawal. Susceptible genes may affect the molecular and biological mechanisms underpinning EF. More specifically, genes associated with the regulation of prefrontal dopamine may modulate the response of prefrontal neurons during executive control. Several studies with adults and older children have shown that variants of the catechol-O-methyltransferase (COMT) gene are associated with behavioral performance and prefrontal activations in EF tasks. However, the effect of the COMT genotype on prefrontal activations during EF tasks on young children is still unknown. The present study examined whether a common functional polymorphism (Val158Met) in the COMT gene was associated with prefrontal activations and cognitive shifting in 3- to 6-year-old children. The study revealed that, compared with children with at least one Met allele (Met/Met and Met/Val), children who were Val homozygous (i) were more able to flexibly switch rules in cognitive shifting tasks and (ii) exhibited increased activations in lateral prefrontal regions during these tasks. This is the first evidence that demonstrates the relationship between a gene polymorphism and prefrontal activations in young children. It also indicates that COMT Val homozygosity may be advantageous for cognitive shifting and prefrontal functions, at least during early childhood, and children who possess this variant may have a lower risk of developing future cognitive and social development issues.

Goal Attribution toward Non-Human Objects during Infancy Predicts Imaginary Companion Status during Preschool Years.

It has been shown that there is a significant relationship between children's mentalizing skills and creation of an imaginary companion (IC). Theorists have proposed that interaction with an IC may improve mentalizing skills, but it is also possible that children's mentalizing skills affect their creation of an IC. In this longitudinal study, we examined whether goal attribution in infants younger than 1 years old (Time 1) predicted their creation of ICs at 48 months old (Time 2). At Time 1, infants' goal attribution was measured in an action prediction experiment, where infants anticipated three types of action goals: (1) another person's goal-directed action (GH condition); (2) another person's non-goal-directed (BH condition); and (3) a mechanical claw's goal-directed action (MC condition). At Time 2, parents completed questionnaires assessing whether their children had ICs. The path analyses using Bayesian estimation revealed that infants' anticipation in the MC condition, but not in the GH and BH conditions, predicted their later IC status. These results indicate that infants' goal attributions to non-human agents may be a strong predictor of their later IC creation. Early mentalizing skills toward non-human objects may provide children with a basis for their engagement in imaginative play.

My neighbor: children's perception of agency in interaction with an imaginary agent.

Children may treat an invisible entity as a live and thinking entity, known as an imaginary companion (IC). Some researchers suggest that this is simply pretend play, but it is possible that children experience agency in their interactions with ICs. Given the literature on cognitive science and social brain research, we hypothesize that young children may have an agent-perception system that responds to an invisible agent by which they may experience realistic agency in their interactions with ICs. In this study, children were introduced to an invisible agent and an invisible stone. However, they assigned biological and psychological properties to the agent but not the stone. The tendency of assigning such properties was stronger in children with ICs than in those without ICs. These results contribute to our understanding of cognitive and neural development in typical and atypical children.

Cues that trigger social transmission of disinhibition in young children.

Previous studies have shown that observing a human model's actions, but not a robot's actions, could induce young children's perseverative behaviors and suggested that children's sociocognitive abilities can lead to perseverative errors ("social transmission of disinhibition"). This study investigated how the social transmission of disinhibition would occur. Specifically, the authors examined whether a robot with human appearance (an android) triggered young children's perseveration and compared the effects of the android with those of a human model. The results revealed that the android induced the social transmission of disinhibition. Also, children were more likely to be affected by the human model than by the android. The results suggested that behavioral cues (biological movement) may be important for the social transmission of disinhibition.

[The measurement of maternal mind-mindedness: its relation to mother-infant interaction in natural settings].

The purpose of this study was to construct an original video-based measurement of maternal mind-mindedness (MM). MM is mother's proclivity to treat her infant as an individual with mind (Meins, 1997). Participants were 38 mothers and their six-month-old infants. The results of assessment suggested that there were large individual differences not only in frequency of maternal mental attributions, but also in the specific contents that mothers read from the filmed infants' behaviors. Moreover, it was revealed that these individual differences in MM were related to mother-infant interaction styles in natural settings, especially maternal comments on infant's internal state and the followings of infant's attention. Finally, the usefulness of this measurement in examining the effect of MM on the child's development of mind understanding was discussed.