The neurological basis of developmental coordination disorder (DCD) is thought to be deficits in the internal model and mirror-neuron system (MNS) in the parietal lobe and cerebellum. However, it is not clear if the visuo-motor temporal integration in the internal model and automatic-imitation function in the MNS differs between children with DCD and those with typical development (TD). The current study aimed to investigate these differences. Using the manual dexterity test of the Movement Assessment Battery for Children (second edition), the participants were either assigned to the probable DCD (pDCD) group or TD group. The former was comprised of 29 children with clumsy manual dexterity, while the latter consisted of 42 children with normal manual dexterity. Visuo-motor temporal integration ability and automatic-imitation function were measured using the delayed visual feedback detection task and motor interference task, respectively. Further, the current study investigated whether autism-spectrum disorder (ASD) traits, attention-deficit hyperactivity disorder (ADHD) traits, and depressive symptoms differed among the two groups, since these symptoms are frequent comorbidities of DCD. In addition, correlation and multiple regression analyses were performed to extract factors affecting clumsy manual dexterity. In the results, the delay-detection threshold (DDT) and steepness of the delay-detection probability curve, which indicated visuo-motor temporal integration ability, were significantly prolonged and decreased, respectively, in children with pDCD. The interference effect, which indicated automatic-imitation function, was also significantly reduced in this group. These results highlighted that children with clumsy manual dexterity have deficits in visuo-motor temporal integration and automatic-imitation function. There was a significant correlation between manual dexterity, and measures of visuo-motor temporal integration, and ASD traits and ADHD traits and ASD. Multiple regression analysis revealed that the DDT, which indicated visuo-motor temporal integration, was the greatest predictor of poor manual dexterity. The current results supported and provided further evidence for the internal model deficit hypothesis. Further, they suggested a neurorehabilitation technique that improved visuo-motor temporal integration could be therapeutically effective for children with DCD.

Lesions to brain regions such as the temporoparietal junction (TPJ) and inferior frontal cortex (IFC) are thought to cause autism-spectrum disorder (ASD). Previous studies indicated that transcranial direct current stimulation (tDCS) of the right TPJ improves social cognitive functions such as imitation-inhibition and perspective-taking. Although previous work shows that tDCS of the right IFC improves imitation-inhibition, its effects on perspective-taking have yet to be determined. In addition, the role of the TPJ and IFC in determining the Autism-Spectrum Quotient (AQ), which is a measure of autism spectrum traits, is still unclear. Thus, the current study performed tDCS on the right TPJ and the right IFC of healthy adults, and examined its effects on imitation-inhibition, perspective-taking, and AQ scores. Based on previous studies, we hypothesized that anodal tDCS of the right IFC and right TPJ would improve imitation-inhibition, perspective-taking, and the AQ score. Anodal tDCS of the right TPJ or IFC significantly decreased the interference effect in an imitation-inhibition task and the cost of perspective-taking in a perspective-taking task, in comparison to the sham stimulation control. These findings indicated that both the TPJ and the IFC play a role in imitation-inhibition and perspective-taking, i.e. control of self and other representations. However, anodal stimulation of the right TPJ and the right IFC did not alter participants’ AQ. This finding conflicts with results from previous brain imaging studies, which could be attributed to methodological differences such as variation in sex, age, and ASD. Therefore, further research is necessary to determine the relationship between the TPJ and IFC, and the AQ.

Although visuo-motor temporal integration in children is suggested to be related to motor control and motor learning, its relevance is still unclear. On the other hand, visuo-motor temporal integration ability undergoes developmental changes with age. In the current correlational study, we measured manual dexterity and visuo-motor temporal integration ability in 132 children with typical development (age, 4–15 years) and investigated the relationship between the two functions. The Movement Assessment Battery for Children-2nd edition was used as an indicator of manual dexterity. The delay detection threshold (DDT) and steepness of the probability curve for delay detection, which was measured by the delayed visual feedback detection task for self-generated movement, were used as indices of the visuo-motor temporal integration ability. The results indicated significant correlations between manual dexterity/age and DDT/steepness of the probability curve for delay detection. In addition, hierarchical multiple regression analysis showed that both manual dexterity and age significantly contributed to visuo-motor temporal integration, indicating a better fit than when only age was employed as an independent variable. Importantly, there was no interaction effect between age and manual dexterity. These findings were the first to suggest that manual dexterity is a significant predictor of visuo-motor temporal integration ability in children, regardless of age. The present study validated the important relationship between visuo-motor temporal integration and manual dexterity in children. Considering the limitations of the current study, including the non-homogeneous sample, further studies are still warranted to validate the results.

Children with cerebral palsy (CP) often exhibit mental health problems, such as depressive symptoms. The purpose of this study was to describe the self-rated depressive symptoms in children with and without CP and to investigate the associated predictors. Participants included 24 children with CP and 33 typically developing (TD) children. Depressive symptoms were assessed using the Birleson Depression Self-Rating Scale for Children. Parents of the participants completed the Strengths and Difficulties Questionnaire. Severity of self-rated depressive symptoms was higher in children with CP than that in TD children. Particularly, decline in activities and enjoyment was identified as a contributor to the increased severity of depressive symptoms. Hierarchical multiple regression analysis revealed that the greater severity of depressive symptoms in children with CP was mediated by hyperactivity/inattention and peer problems. Our study suggests that it is imperative to provide opportunities to participate in social activities from an early age.

Children with developmental disorders often have poor motor performance. This study aimed to address the association between tactile localization ability, an indicator of body image, and motor function in children with motor deficits. Eighteen children with motor deficits participated, and their upper and lower limbs were assessed. To assess the level to which the patient's body image was developed, a tactile localization task (TLT) was used. In the TLT, experimenters touched a child's fingers, toes, or lower extremities (L/E), and the participants were asked to identify the location of the touch on a body part illustration. We compared TLT ability between high and low motor function groups, and investigated the correlation between TLT and the measures of motor function, age, and non-verbal intelligence. The high motor function group had significantly higher L/E TLT scores than the low motor function group, except in the tests involving the fingers and toes. Furthermore, the L/E TLT correlated only with motor function measures (Gross Motor Function Measure score, measured using one-leg standing time and one-leg hopping ability). The results suggest that children with motor deficits experience developmental delay in terms of their body image.