Action-outcome Regularity Perceptual Sensitivity in Children with Developmental Coordination Disorder.

PURPOSE: An internal model deficit is considered to underlie developmental coordination disorder (DCD); thus, children with DCD have an altered sense of agency (SoA), which is associated with depressive symptoms. Furthermore, the perception of action-outcome regularity is present in early development, is involved in the generation of SoA, and has roles in adaptive motor learning and coordinated motor skills. However, perceptual sensitivity to action-outcome regularity has not been examined in children with DCD. METHODS: We investigated perceptual sensitivity to action-outcome regularity in 6-15-year-old children with DCD and age- and sex-matched typically developing (TD) children. Both groups were assessed for coordinated motor skills with the Movement Assessment Battery for Children-2nd Edition, while the DCD group was assessed with the DCD Questionnaire, Social Communication Questionnaire, Attention-Deficit/Hyperactivity Disorder-Rating Scale, and Depression Self- Rating Scale for Children. RESULTS: Perceptual sensitivity to action-outcome regularity was significantly reduced in children with DCD. However, there was a significant correlation between perceptual sensitivity to action-outcome regularity and age in DCD and TD children. Perceptual sensitivity to action-outcome regularity was significantly lower in younger children with DCD than in younger and older TD children, but there were no significant differences between older children with DCD and younger and older TD children. CONCLUSION: The current results suggest that children with DCD have significantly reduced perceptual sensitivity to action-outcome regularity at younger ages, which may alter SoA and inhibit internal model development, thereby reducing motor skill coordination.

Cognitive Orientation to Daily Occupational Performance: A Randomized Controlled Trial Examining Intervention Effects on Children with Developmental Coordination Disorder Traits.

Children with traits of developmental coordination disorder (DCD-t) may experience occupational performance problems that go unrecognized and therefore may not be adequately supported. The cognitive orientation to daily occupational performance (CO-OP) approach has been effective in interventions for developmental coordination disorder (DCD). Based on an open-label, randomized controlled trial design, this study evaluated the effects of CO-OP on the occupational performance and motor skills of older kindergarten children with DCD-t using the School Assessment of Motor and Process Skills (S-AMPS) and the Movement Assessment Battery for Children, Second Edition. Children with a total DCDQ score of less than 40 or M-ABC2 scores in the 5th to 16th percentile were considered to have DCD-t. Furthermore, children with DCD-t and S-AMPS process skills less than 0.7 were considered to have DAMP (Deficits in Attention, Motor control and Perception)-t. After 3 months of CO-OP intervention, the performance and motor skills of children with DCD-t improved significantly. However, there were no significant changes noted in the motor skills of children with DAMP-t, although their occupational performance improved. These results suggest that CO-OP is effective even for older kindergarten children with DCD-t. However, further improvement of the CO-OP approach or a different strategy is required for children with ADHD comorbidity.

Decreased walking efficiency in elementary school children with developmental coordination disorder trait.

OBJECTIVE: To compare walking efficiency, and associated physical function, between children, with and without developmental coordination disorder trait. DESIGN: Cross-sectional study. SETTING: The study was conducted in a Medical and Rehabilitation Center for Developmental Disabilities in Okazaki, Japan. SUBJECTS: The study included 286 children, 6-12 years of age, with and without developmental coordination disorder trait. Developmental coordination disorder trait was defined by a score below the -1 standard deviation on the Japanese version of the Developmental Coordination Disorder Questionnaire. Based on this criterion, 45 children (28 boys) were classified into the developmental coordination disorder trait group and the other 241 (115 boys) in the control group. MEASURES: The following physical function outcomes were measured: single leg stance test; step length variability; and walking efficiency, measured using the 2-min walk test. Logistic regression analysis was used to determine the association between developmental coordination disorder trait and lower walking efficiency and physical function. RESULTS: Compared to the control group, the developmental coordination disorder group showed lower walking efficiency (P = 0.026), higher step length variability (P = 0.047), and shorter single leg stance test (P = 0.001). Developmental coordination disorder was independently associated with walking efficiency (odds ratio, 1.03; 95% confidence interval [CI], 1.001-1.061; P = 0.041) and single leg stance test (odds ratio, 0.99; 95% CI, 0.978-0.996; P = 0.006), but not to step length variability, age, and sex. CONCLUSIONS: Lower walking efficiency increases energy expenditure in children with developmental coordination disorder trait. Interventions to improve walking efficiency could improve the physical function and participation of these children.

Developmental changes in action-outcome regularity perceptual sensitivity and its relationship to hand motor function in 5-16-year-old children.

Along with the comparator model, the perception of action-outcome regularity is involved in the generation of sense of agency. In addition, the perception of action-outcome regularity is related to motor performance. However, no studies have examined the developmental changes in the perception of action-outcome regularity. The current study measured perceptual sensitivity to action-outcome regularity and manual dexterity in 200 children aged between 5 and 16 years. The results showed that perceptual sensitivity to action-outcome regularity was significantly lower in 5-6-year-old children than in 9-16-year-old children, and that it was significantly lower in children with low manual dexterity than in children with medium to high manual dexterity. Correlation analyses revealed significant correlations of age and perceptual sensitivity to action-outcome regularity, but no significant correlation of manual dexterity and perceptual sensitivity to action-outcome regularity, either overall or in any age band. The present study suggests that perceptual sensitivity to action-outcome regularity is immature at 5-6 years of age and that it may be impaired in 5-16-year-old children with poor manual dexterity.

Spatial Instability during Precision Grip-Lift in Children with Poor Manual Dexterity.

Although children with developmental coordination disorder (DCD) show impaired precision grip control due to a sensory-motor integration deficit, their spatial instability (such as changes in force direction and object roll during a precision grip task) is unclear. Herein, we investigated the spatial instability in the precision grip force control of children with poor manual dexterity. We divided 66 school-aged children who performed a precision gripping and lifting of heavy- or lightweight objects into those with low manual dexterity (n = 11) and those with high manual dexterity (n = 55) as revealed by the Movement Assessment Battery for Children (2nd edition). The group and weight effects were then determined. The results revealed that the total trajectory lengths of the center of pressure (COP) were longer in the lightweight object data of the children in the low-manual-dexterity group and were related to the children's grip force. The low-manual-dexterity group also showed a shifted COP position from the center of the object in the medial-lateral direction and in the object roll regardless of the object's weight; these were closely related in both weights' tests. These results demonstrated that children with poor manual dexterity show spatial instability and different adaptations to the weight of objects during a precision grip task. Further studies are needed to determine whether these findings would be replicated in children with a diagnosis of DCD.

The Relationship between Motor Coordination Ability, Cognitive Ability, and Academic Achievement in Japanese Children with Autism Spectrum Disorder and Attention Deficit/Hyperactivity Disorder.

Motor coordination abilities are related to cognitive abilities and academic achievement in children with neurodevelopmental disorders. However, the similarities and differences of these relationships in children with autism spectrum disorder (ASD) and attention deficit/hyperactivity disorder (AD/HD) have not been explored. The purpose of this study was to investigate the relationship between motor coordination abilities, cognitive abilities, and academic achievement in Japanese children with ASD and AD/HD. Participants included 20 children with ASD, 20 children with AD/HD, and 20 typically developing children, matched for age and gender. Their motor coordination abilities were assessed with the Movement Assessment Battery for Children-2 (MABC-2). Furthermore, cognitive ability and academic achievement were assessed with the Kauffman Assessment Battery for Children-II (K-ABCII). Results demonstrated that the MABC-2 Total score significantly correlated with the K-ABCII Simultaneous processing, Planning, Total cognitive ability, Writing and Arithmetic scores in children with ASD. However, in children with AD/HD, there was no significant correlation between MABC-2 and K-ABCII subscale scores. The results of this study indicated that the relationship between motor coordination ability, cognitive ability, and academic achievement differs between ASD and AD/HD. This difference might indicate the non-similarity of neurological characteristics and encourage consideration for an approach that accommodates the features of neurodevelopmental disorders in children.

Emotional and behavioral problems in Japanese preschool children with motor coordination difficulties: the role of autistic traits.

There has been little research on whether younger children with developmental coordination disorder (DCD) symptoms have an increased risk for emotional and behavioral problems. This study examined whether coordination difficulties are associated with emotional and behavioral problems (emotional symptoms, conduct problems, hyperactivity/inattention, peer problems, reduced prosocial behavior) in preschool children and the role of autistic traits in this association. Data (N = 1042, age 58-71 months) were analyzed from the Tama Children's Survey (TCS). The Little Developmental Coordination Disorder Questionnaire (LDCDQ) was used to measure coordination difficulty symptoms. Information was obtained on emotional/behavioral problems using the Strengths and Difficulties Questionnaire (SDQ) and on autistic traits with the Social Responsiveness Scale (SRS). Higher autistic traits were based on SRS cutoff scores (53.5 for boys and 52.5 for girls). Logistic regression analysis was used to assess associations between the variables. In adjusted models, children with probable DCD (pDCD) were significantly more likely to score above the clinical thresholds on all SDQ emotional/behavioral domains. However, nearly all of these associations became nonsignificant after including autistic traits in the analysis. Additional analyses showed that children with pDCD with higher autistic traits had significantly increased odds for emotional problems (odds ratio [OR]: 4.47, 95% confidence interval [CI]: 1.52-13.19), hyperactivity/inattention (OR: 3.74, 95% CI: 1.45-9.64), peer problems (OR: 15.81, 95% CI: 5.96-41.99), and total difficulties (OR: 28.78, 95% CI: 7.23-114.57), compared to children with pDCD alone. These results indicate that the increased risk of emotional/behavioral difficulties in preschool children with pDCD might be mediated by autistic traits.

Bilateral asymmetry in the gait deviation index in school-aged children with the trait of developmental coordination disorder.

BACKGROUND: Although previous studies have identified asymmetry in gait parameters in children with developmental coordination disorder (DCD), they have not investigated whether these findings coexist with asymmetry in gait quality, as represented by the gait deviation index (GDI). RESEARCH QUESTION: This study sought to measure gait symmetry in children with traits of DCD (DCD trait) to elucidate the characteristic gait pattern. METHODS: This study included 172 (82 girls, 90 boys) participants with and without DCD trait (age: 6-12 years), as assessed using the Japanese version of the Developmental Coordination Disorder Questionnaire (DCDQ-J), which consists of three subscales. Three-dimensional gait analysis data were obtained during the gait trials. GDI, step length, and step time data were recorded for both the right and left legs, and symmetry ratios were calculated. RESULTS: Participants in the DCD trait group (n = 30) had a significantly lower GDI score (p < 0.0001) and a higher GDI symmetry ratio (p = 0.004) than typically developing children. Furthermore, DCD trait was related to the GDI symmetry ratio (odds ratio, 1.2; p = 0.001; 95 % confidence interval, 1.062-1.289). The control during movement, which was a DCDQ-J subscale, was negatively correlated with the GDI symmetry ratio (r=-0.257, p<0.001). SIGNIFICANCE: This study's results lend support to the hypothesis that an increase in the GDI symmetry ratio is associated with the DCD trait. A quantitative assessment of gait performance is important to help identify gait asymmetry, including gait quality, in children with a DCD trait. Children with a DCD trait have a poor ability to control the interaction of lower leg movements, which may cause bilateral asymmetry in gait quality.

Influence of Stochastic Resonance on Manual Dexterity in Children With Developmental Coordination Disorder: A Double-Blind Interventional Study.

Background: There is increasing evidence that the stochastic resonance (SR) phenomenon provided by subthreshold mechanical noise stimulation improves the sensory-motor system. However, the effect of SR on children with developmental coordination disorder (DCD) is unclear. The purpose of this study was to assess whether SR activated by subthreshold vibrotactile noise stimulation of the wrist influences manual dexterity in children with DCD. Methods: A double-blind interventional study was conducted. Participants were 30 children (age: 9.3 ± 1.44 years, range 6-11 years; 27 male, three female; 25 right-handed, five left-handed) meeting DCD diagnostic criteria in DSM-5. The manual dexterity test was administered the day before SR intervention (baseline-data). SR was elicited using subthreshold vibrotactile noise stimulation at 60% of the vibrotactile threshold measured at the wrist. SR was delivered two times and the manual dexterity test was administered during each SR stimulation block (SR-on condition) and after each SR stimulation block (SR-off), for a total of four measurements. Target outcomes were the component score, the standard score, and the percentile score of the manual dexterity test. Results: The manual dexterity test scores in the SR-on condition were significantly improved compared to scores at the baseline and in the SR-off condition (p < 0.001). Conclusions: The present study showed that subthreshold noise stimulation eliciting SR significantly improved manual dexterity outcomes in children with DCD during stimulation but not after stimulation. Future studies will need to investigate the carry-over effects of SR stimulation.

Fine and gross motor skills predict later psychosocial maladaptation and academic achievement.

BACKGROUND: Difficulties in fine and gross motor skills are often overlooked as developmental problems, although approximately 6-13% of all school-age children have poor motor coordination. Understanding motor coordination is important from the perspective of school adaptation. This longitudinal cohort study aimed to determine whether fine and gross motor skills in preschool children predict later academic achievement and psychosocial maladaptation. METHODS & PROCEDURES: Participants were 2,501 children from nursery and elementary schools (5-13 years old). The motor skills of preschool children were assessed by their nursery teacher immediately before entering elementary school. The Strengths and Difficulties Questionnaire and a standardized Japanese test were administered annually throughout elementary school. RESULTS: Early motor difficulties in preschool children had significant effects on their academic achievement and psychosocial maladaptation up until the sixth grade. Gross motor difficulties in preschool were associated with the later peer problems and worsened emotional symptoms. CONCLUSIONS: Motor skills in preschool children are useful as a predictor of later psychosocial maladaptation and academic achievement.

Increased visual bias in children with developmental coordination disorder: Evidence from a visual-tactile temporal order judgment task.

BACKGROUND: Previous studies have suggested that children with developmental coordination disorder (DCD) rely heavily on vision to perform movements, which may contribute to their clumsy movements. However, few studies have objectively and quantitatively investigated the perceptual biases of children with DCD. METHODS: A visual-tactile temporal order judgment (TOJ) task was used to measure and compare the perceptual biases of 19 children with DCD and 19 age- and sex-matched typically developing children. The point of subjective equality, which demonstrates when "visual first" and "tactile first" judgment probabilities are equal (50%), obtained by analyzing the results of the visual-tactile TOJ task, was used as an indicator of perceptual biases. Further, variables (age and manual dexterity in all participants; motor function, autism spectrum disorder and attention-deficit hyperactivity disorder traits, and depressive symptoms in children with DCD) associated with perceptual biases were examined with correlation analysis. RESULTS: Children with DCD had significantly stronger visual bias than typically developing children. Overall correlation analysis showed that increased visual bias was significantly correlated with poor manual dexterity. CONCLUSION: Children with DCD had a strong visual bias, which was associated with poor manual dexterity.

Neonatal irritable sleep-wake rhythm as a predictor of autism spectrum disorders.

Recently, it has been suggested that sleep problems in autism spectrum disorder (ASD) not only are associated symptoms, but may be deeply related to ASD pathogenesis. Common clinical practice relating to developmental disorders, has shown that parents of children with ASD have often stated that it is more difficult to raise children in the neonatal period because these children exhibit sleep problems. This study investigated the possibility that abnormal neonatal sleep-wake rhythms are related to future ASD development. We administered questionnaires to assess parent(s) of children with ASD and controls. A retrospective analysis was conducted among 121 children with ASD (94 male and 27 female children) recruited from the K-Development Support Center for Children (K-ASD), 56 children with ASD (40 male and 16 female children) recruited from the H-Children's Sleep and Development Medical Research Center (H-ASD) and 203 children (104 male and 99 female children) recruited from four nursery schools in T-city (control). Irritable/over-reactive types of sleep-wake rhythms that cause difficulty in raising children, such as 1) frequently waking up, 2) difficulty falling asleep, 3) short sleep hours, and 4) continuous crying and grumpiness, were observed more often in ASD groups than in the control group. Additionally, the number of the mothers who went to bed after midnight during pregnancy was higher in the ASD groups than in the control group. Sleep-wake rhythm abnormalities in neonates may be considerable precursors to future development of ASD. Formation of ultradian and postnatal circadian rhythms should be given more attention when considering ASD development. Although this is a retrospective study, the results suggest that a prospective study regarding this issue may be important in understanding and discovering intervention areas that may contribute to preventing and/or properly treating ASD.

Altered sense of agency in children with developmental coordination disorder.

BACKGROUND: There is increasing evidence that children with developmental coordination disorder (DCD) have deficits in sensory-motor integration, but it is unclear whether the sense of agency (SoA) generated by sensory-motor integration is altered. AIMS: To investigate whether there is a difference in the time window for SoA between children with DCD and typically developing (TD) children. METHODS AND PROCEDURES: An agency attribution task was used to quantitatively measure and compare the time window for SoA in 15 children with DCD and 46 children in the TD group. Variables that correlated with the time window for SoA were also examined in both groups of children. OUTCOMES AND RESULTS: The time window for SoA was significantly extended in children with DCD compared to TD children. The time window for SoA in TD children was significantly associated with manual dexterity, whereas the time window for SoA in children with DCD was significantly associated with depressive tendency. CONCLUSIONS AND IMPLICATIONS: The time window for SoA is altered in children with DCD. The present results suggest that there may be a bidirectional relationship between an internal model deficit and depressive tendency and SoA in children with DCD.

Risk factors for motor coordination problems in preschool-age children.

BACKGROUND: Motor coordination problems (MCP) in children can sometimes be diagnosed as developmental coordination disorder. Early intervention for developmental coordination disorder is necessary because it often continues into adolescence, causing mental and physical complications. Few studies have investigated the prevalence of childhood MCP in the Japanese population, examining the risk factors for MCP. We therefore investigated the prenatal factors associated with MCP in preschool-age children. METHODS: This study was based on a prospective cohort study, the Hokkaido Study on Environment and Children's Health. Mothers of 4,851 children who reached the age of 5 years within the study-period received questionnaires, including the Japanese version of the Developmental Coordination Disorder Questionnaire (DCDQ-J). We examined the risk factors associated with MCP using logistic regression analysis. RESULTS: Of 3,402 returned DCDQ-J questionnaires, 3,369 were answered completely. From the 3,369 children, we categorized having MCP by using two cut-off scores: that of the DCDQ'07 and the cut-off at the 5th percentile of a total DCDQ-J score. Comparing children with and without MCP, we found significant differences in the education level of the mothers, annual household income during pregnancy, maternal alcohol consumption and smoking during pregnancy, and sex and age of the children at the time of completing the DCDQ-J by both categorizations. Adjusted logistic regression analysis revealed that maternal smoking during the first trimester of pregnancy and male sex were significantly associated with MCP. CONCLUSIONS: Our results suggest that maternal smoking during pregnancy is the main factor associated with MCP in preschool-age children.

Manual Dexterity is not Related to Media Viewing but is Related to Perceptual Bias in School-Age Children.

Although the media can have both negative and positive effects on children's cognitive and motor functions, its influence on their perceptual bias and manual dexterity is unclear. Thus, we investigated the association between media viewing time, media preference level, perceptual bias, and manual dexterity in 100 school-aged children. Questionnaires completed by children and their parents were used to ascertain media viewing time and preference levels. Perceptual bias and manual dexterity were measured using the visual-tactile temporal order judgment task and Movement Assessment Battery for Children-2nd edition, respectively. There were significant positive correlations between age and media viewing time and between media viewing time and media preference level. There was also a significant negative correlation between visual bias and manual dexterity. Hierarchical multiple regression analysis revealed that increasing visual bias was a significant predictor of decreasing manual dexterity. Further, children with low manual dexterity showed significant visual bias compared to those with high manual dexterity, when matched for age and gender. The present results demonstrated that, in school-aged children, although viewing media was not associated with perceptual bias and manual dexterity, there was a significant association between perceptual bias and manual dexterity.

Subthreshold Vibrotactile Noise Stimulation Immediately Improves Manual Dexterity in a Child With Developmental Coordination Disorder: A Single-Case Study.

Developmental coordination disorder (DCD) is the most common childhood movement disorder. It is characterized by clumsiness of fine and gross motor skills in developing children. Children with DCD have low ability to effectively use tactile information for movements, instead relying on visual information. In addition, children with DCD have deficits in visuo-motor temporal integration, which is important in motor control. These traits subsequently lead to clumsiness of movements. Conversely, however, imperceptible vibrotactile noise stimulation (at 60%-intensity of the sensory threshold) to the wrist provides stochastic resonance (SR) phenomenon to the body, improving the sensory and motor systems. However, the effects of SR have not yet been validated in children with DCD. Thus, we conducted a single case study of a 10-year-old boy with a diagnosis of DCD to investigate the effect of SR on visual dependence, visuo-motor temporal integration, and manual dexterity. SR was provided by vibrotactile noise stimulation (at an intensity of 60% of the sensory threshold) to the wrist. Changes in manual dexterity (during the SR on- and off-conditions) were measured using the manual dexterity test of the Movement Assessment Battery for Children-2nd edition. The point of subjective equality measured by visual or tactile temporal order judgment task served as a quantitative indicator reflecting specific sensory dependence. The delay detection threshold and steepness of delay detection probability curve, which were measured using the delayed visual feedback detection task, were used as quantitative indicators of visuo-motor temporal integration. The results demonstrated alleviated visual dependence and improved visuo-motor temporal integration during the SR on-conditions rather than the SR off-conditions. Most importantly, manual dexterity during the SR on-conditions was significantly improved compared to that during the SR off-conditions. Thus, the present results highlighted that SR could contribute to improving poor movement in children with DCD. However, since this was a single case study, a future interventional study with a large sample size is needed to determine the effectiveness of SR for children with DCD.

Stochastic resonance improves visuomotor temporal integration in healthy young adults.

Mechanical and electrical noise stimulation to the body is known to improve the sensorimotor system. This improvement is related to stochastic resonance (SR), a phenomenon described as a "noise benefit" to various sensory and motor systems. The current study investigated the influence of SR on visuomotor temporal integration and hand motor function under delayed visual feedback in healthy young adults. The purpose of this study was to measure the usefulness of SR as a neurorehabilitation device for disorders of visuomotor temporal integration. Thirty healthy volunteers underwent detection tasks and hand motor function tests under delayed visual feedback, with or without SR. Of the 30 participants, 15 carried out the tasks under delayed visual feedback in the order of SR on-condition, off-condition, off-condition, and on-condition. The remaining 15 participants conducted the experimental tasks in the order of SR off-condition, on-condition, on-condition, and off-condition. Comparisons of the delay detection threshold (DDT), steepness of the delay detection probability curves, box and block test (BBT) scores, and nine-hole peg test (NHPT) scores between the SR on- and off-conditions were performed. The DDT under the SR on-condition was significantly shortened compared with the SR off-condition. There was no significant difference between the SR on- and off-conditions for the steepness of the delay detection probability curves, BBT scores, and NHPT scores. SR improved visuomotor temporal integration in healthy young adults, and may therefore improve movement disorders in patients with impaired visuomotor temporal integration. However, because the current results showed that SR did not improve hand motor function under delayed visual feedback, it may not improve motor function when a large distortion of visuomotor temporal integration is present. Further studies are required considering several limitations of the current study, and future clinical trials are necessary to verify the effects of motor training using SR for the treatment of visuomotor temporal integration disorders.

Applicability of the Movement Assessment Battery for Children-Second Edition (MABC-2) for Japanese Children Aged 3-6 Years: A Preliminary Investigation Emphasizing Internal Consistency and Factorial Validity.

This study investigated the applicability of the Movement Assessment Battery for Children - Second Edition (MABC-2) for 3- to 6-year-old Japanese children, particularly addressing its internal consistency and factorial validity. The MABC-2 test set for 3- to 6-year-old children was administered to 252 children. Differences between Japanese children and those of the original normative sample (i.e. United Kingdom children) were investigated along with sex differences. The Japanese children aged 3-6 years were found to have higher Manual Dexterity and Balance component scores than children of the normative sample. Girls scored higher than boys on the Balance component. Results of several analyses showed good internal consistency of the MABC-2. Confirmatory factor analysis revealed that a theoretical three-component model of the MABC-2 was not fitted to Japanese children aged 3-6 years. Instead, a new three-component model was postulated and discussed. The new three-component model of the MABC-2, with Manual Dexterity, Static Balance and Ball Skills, and Dynamic Balance, has high factorial validity in Japanese children aged 3-6 years.

Manual Dexterity Is a Strong Predictor of Visuo-Motor Temporal Integration in Children.

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.

Deficits in Visuo-Motor Temporal Integration Impacts Manual Dexterity in Probable Developmental Coordination Disorder.

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.