The Structure of Working Memory and Its Relationship with Intelligence in Japanese Children.

There is a host of research on the structure of working memory (WM) and its relationship with intelligence in adults, but only a few studies have involved children. In this paper, several different WM models were tested on 170 Japanese school children (from 7 years and 5 months to 11 years and 6 months). Results showed that a model distinguishing between modalities (i.e., verbal and spatial WM) fitted the data well and was therefore selected. Notably, a bi-factor model distinguishing between modalities, but also including a common WM factor, presented with a very good fit, but was less parsimonious. Subsequently, we tested the predictive power of the verbal and spatial WM factors on fluid and crystallized intelligence. Results indicated that the shared contribution of WM explained the largest portion of variance of fluid intelligence, with verbal and spatial WM independently explaining a residual portion of the variance. Concerning crystallized intelligence, however, verbal WM explained the largest portion of the variance, with the joint contribution of verbal and spatial WM explaining the residual part. The distinction between verbal and spatial WM could be important in clinical settings (e.g., children with atypical development might struggle selectively on some WM components) and in school settings (e.g., verbal and spatial WM might be differently implicated in mathematical achievement).

Reduced Nogo-P3 in adults with developmental coordination disorder (DCD).

Nogo-N2 is associated with the premotor cognitive process that precedes motor response (e.g., conflict monitoring), whereas Nogo-P3 is related to the inhibition of the actual motor response. We examined the influence of motor clumsiness of developmental coordination disorder (DCD) on components of the event-related potential in a Go/Nogo task. Participants were healthy adults (N = 81) that were classified into control and DCD groups based on the Movement Assessment Battery for Children Second Edition. We manipulated the difficulty in stopping a response by varying the frequency of Nogo stimuli in a response task into rare (20%) and frequent (80%) conditions, and Nogo-N2 and Nogo-P3 were calculated from electroencephalograms (EEGs) during the Go/Nogo tasks. The commission error rate in the rare condition was significantly higher in the DCD group than in the control group, indicating that motor clumsiness decreases task performance. There were no differences in Nogo-N2 between DCD and control groups. However, Nogo-P3 in the rare condition was reduced in the DCD group compared to the control group. These results suggest that the influence of motor clumsiness is limited to the cognitive process after the initiation of the actual motor response.

Discrepancy between musical ability and language skills in children with Williams syndrome.

BACKGROUND: Children with Williams syndrome (WS) show a marked interest in music, a characteristic often explored in clinical settings. However, the actual musical abilities of patients with WS remain debatable due to some of the relevant data being derived from experimental tasks that require a verbal response, despite the known language impairments in WS. The present study aimed to examine musical ability in children with WS using a newly invented pitch discrimination task with minimal involvement of language and clarify its relationship with language skill. METHODS: Eleven children with WS participated in the study. We used a novel pitch discrimination task that required minimal language use. Two piano tones were presented sequentially, and children were asked to give a non-verbal response as to whether the second tone was higher than, lower than, or the same as the first tone. RESULTS: Pitch discrimination performance in children with WS was lower than the level predicted for their chronological age (CA), even in the non-verbal task. Pitch discrimination ability and verbal mental age (VMA) were shown to be dissociated, such that children with WS with a lower skill level for language showed an unexpectedly higher level of pitch discrimination ability and vice versa. CONCLUSIONS: Our results indicated reduced musical ability with respect to CA in children with WS. The dissociation between musical ability and language skills may indicate unique developmental relationships that differ from those in normal children. These findings provide new evidence to support the importance of assessing actual musical ability in WS prior to implementing interventional music therapy.

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.

Role of Inner Speech on Serial Recall in Children with ASD: A Pilot Study Using the Luria Hand Test.

This study was conducted to investigate the relation between the effect of articulatory suppression on the serial recall and severity of social impairments among children with autism spectrum disorders (ASD). The Luria hand test (LHT) was administered to evaluate the capacity for serial recall in 13 children with ASD. The LHT was administered under three conditions: control, under articulatory suppression, and under spatial suppression. Performance on the LHT of children with ASD was significantly lower in terms of both articulatory suppression and the spatial suppression condition. Moreover, the severity of social impairment in children with ASD was related to individual differences of effects of articulatory suppression on the LHT, but not with effects of spatial suppression. These results support the notion that dialogic inner speech which mediates complex cognitive abilities has inherently social origins.

Right prefrontal cortex specialization for visuospatial working memory and developmental alterations in prefrontal cortex recruitment in school-age children.

OBJECTIVE: The right prefrontal cortex (PFC) plays an essential role in active processing within visuospatial working memory (VSWM). The aim of this study was to examine developmental changes in the recruitment patterns of the PFC during visuospatial memory tasks in school-age participants. METHODS: We recruited 80 school-age children who were classified into three age groups: 7- to 8-year-old, 9- to 10-year-old, and 11- to 12-year-old children. We used near infrared spectroscopy (NIRS) to measure PFC activity during visuospatial memory task. Memory stimuli were presented either sequentially or simultaneously. RESULTS: In all three groups, right-lateralized PFC activity was observed during sequential presentation, suggesting specialization of the right PFC for VSWM. During simultaneous presentation, right-lateralized PFC activity was not observed in 7- to 8-year-old children or 9- to 10-year-old children. In contrast, PFC activity was right-lateralized in 11- to 12-year-old children. CONCLUSIONS: We suggest that specialization of the right PFC for VSWM is already present before school-age, but widely distributed activity in response to visuospatial memory tasks changes to more focal activity in VSWM-specific regions during the early school years. SIGNIFICANCE: Using NIRS, we showed developmental changes in the recruitment patterns of the PFC during visuospatial memory tasks.

Spatial working memory encoding type modulates prefrontal cortical activity.

Spatial working memory (SWM) involves both simultaneous and sequential encoding, but the differences in their neural correlates are unclear. We investigated the differences in prefrontal cortex activity related to these SWM encoding types. We also examined the patterns of brain activity influencing individual visuospatial abilities (VSA). We conducted SWM tasks with two different conditions, sequential and simultaneous encoding, and examined hemodynamic activity in 39 healthy adults using near-infrared spectroscopy. The bilateral dorsolateral prefrontal cortex was activated more strongly in the sequential condition compared with the simultaneous condition. This suggests that prefrontal cortex activity underlying SWM is modulated by the type of encoding. We also found that individuals with high VSA showed weaker activation in the right-dorsolateral prefrontal cortex compared with those with lower VSA during the simultaneous condition. This hypoactivation is thought to reflect neural efficiency in the individuals with high ability. These findings are expected to lead to a better understanding of neural substrates for SWM.

Uniqueness of action monitoring in children with autism spectrum disorder: Response types and temporal aspects.

BACKGROUND: Action monitoring, the process for evaluating the appropriateness of one's own actions, is reported to be atypical in individuals with autism spectrum disorder (ASD). METHOD: We examined the characteristics of action monitoring in 11 children with ASD and 12 children with typical development (TD), analyzing stimulus-locked and response-locked event-related potential components (i.e., N2; error-related negativity, ERN; and error positivity, Pe) related to execution of a flanker task. RESULTS: We found a smaller N2 amplitude in children with ASD than in those with TD. Children with ASD also had a larger amplitude of ERN for partial error responses (electromyographic activity corresponding to the inappropriate hand side before response execution) than did children with TD. Additionally, the ERN amplitude for the partial error response was correlated with the Autistic Mannerisms of the Social Responsiveness Scale. There were no significant differences in Pe amplitudes between children with ASD and those with TD. CONCLUSION: The results suggest that action monitoring in children with ASD is significantly different both before and after response execution. We hypothesized that the detail-focused processing style of ASD reduces the demands of action monitoring before response execution; however, autistic mannerisms evoke excessive concern regarding trivial mistakes after response execution.

Stroop-like interference in the real animal size test and the pictorial animal size test in 5- to 12-year-old children and young adults.

This study examined prepotent response inhibition among 653 5- to 12-year-old children and young adults divided into five age groups: forty-six 5- to 6-year-olds, one hundred fifty-eight 7- to 8-year-olds, one hundred ninety-six 9- to 10-year-olds, one hundred eighty-three 11- to 12-year-olds, and 70 young adults (19- to 22-year-olds). Two paper-and-pencil versions of Stroop-like tasks were administered: the Real Animal Size Test and the Pictorial Animal Size Test. In these tests, participants are presented with pictures of animals (large animals such as an elephant, a giraffe, and a whale vs. small animals such as a frog, a bird, and a squirrel) printed as either big or small images that are mismatched with the animal's real size. Participants are required to decide the size of the animals (big vs. small) based on either the size in real life or the size of the picture. The results indicated the following: (a) The Pictorial Animal Size Test elicited robust interference, whereas the Real Animal Size Test elicited no interference; (b) prepotent response inhibition develops markedly in childhood and between children and young adults; and (c) error correction increased rapidly after age 8. The mechanism of interference and the influence of metacognition on prepotent response inhibition are discussed.

Age-related trends of inhibitory control in Stroop-like big-small task in 3 to 12-year-old children and young adults.

Inhibitory control is the ability to suppress competing, dominant, automatic, or prepotent cognitive processing at perceptual, intermediate, and output stages. Inhibitory control is a key cognitive function of typical and atypical child development. This study examined age-related trends of Stroop-like interference in 3 to 12-year-old children and young adults by administration of a computerized Stroop-like big-small task with reduced working memory demand. This task used a set of pictures displaying a big and small circle in black and included the same condition and the opposite condition. In the same condition, each participant was instructed to say "big" when viewing the big circle and to say "small" when viewing the small circle. In the opposite condition, each participant was instructed to say "small" when viewing the big circle and to say "big" when viewing the small circle. The opposite condition required participants to inhibit the prepotent response of saying the same, a familiar response to a perceptual stimulus. The results of this study showed that Stroop-like interference decreased markedly in children in terms of error rates and correct response time. There was no deterioration of performance occurring between the early trials and the late trials in the sessions of the day-night task. Moreover, pretest failure rate was relatively low in this study. The Stroop-like big-small task is a useful tool to assess the development of inhibitory control in young children in that the task is easy to understand and has small working memory demand.

Dual task performance of the Stroop color-word test and stepping in place.

This study investigated whether cognitive processing is influenced by stepping in place, particularly according to its frequency. Fourteen healthy young participants performed the Stroop test during stepping in place at various frequencies. Results showed the following: (a) performances on the Stroop test and at stepping in place at 1, 2, and 3 Hz were not so mutually influential, (b) performing the Stroop test degraded the timing of stepping in place at 4 Hz, (c) stepping at 0.5 Hz interfered with the cognitive processing involved with perceiving and naming colors but not with inhibitory control. These results imply that stepping in place is differentially controlled between walking at 1-4 Hz and at 0.5 Hz, the latter of which demands more attention.

Stroop/reverse-Stroop interference in typical development and its relation to symptoms of ADHD.

This study examined prepotent response inhibition among 376 children and young adults divided into five age groups: 23 5-6-year-olds, 80 7-8-year-olds, 72 9-10-year-olds, 98 11-12-year-olds, and 70 young adults (19-24-year-olds). The Stroop/reverse-Stroop test was administered with a manual response. This test measured Stroop interference, which occurred when naming the ink color of the incongruent color word stimuli (for instance the word red printed in blue ink), and the reverse-Stroop interference, which occurred when reading the stimuli. This study also examined the relation between performance on the Stroop/reverse-Stroop test and scores on the ADHD Rating Scale-IV. Results indicated that the Stroop interference decreased with age, whereas the reverse-Stroop interference increased with age. Results also showed that all three scores in the ADHD Rating Scale-IV, two subscale scores of inattentive and hyperactive-impulsive symptoms and a total score, correlated with the Stroop interference, but not with the reverse-Stroop interference in typically developing children. These results indicated the difference in mechanism between the Stroop interference and the reverse-Stoop interference, and suggested that the Stroop interference is strongly correlated with ADHD symptoms in typically developing children.

Age-related change of the mean level and intraindividual variability of saccadic reaction time performance in persons with intellectual disabilities.

The current study examined age-related change of saccadic reaction time (SRT) in persons with intellectual disabilities (ID). Participants were 29 persons with intellectual disabilities aged between 14 and 34 years whose IQs were between 14 and 70. Participants were divided into Group I (IQ≧35) and Group II (IQ≦34). The mean and the standard deviation of SRT (SRTM and SRTSD, respectively) reduced through adolescence in both groups. This result suggests that the speed and stability of information processing develops during adolescence irrespective of the level of ID. Although SRTM and SRTSD of Group I stabilized after adolescence, those of Group II increased after their thirties. This outcome indicates that persons with severe ID may show signs of the aging process. The results of multiple regression analyses and path analyses indicated that SRTM was influenced by both the speed of information processing and the variability of the response. However, given that the extent of increase of SRTSD in Group II was smaller as compared with that of SRTM, this increase of SRTM after the thirties in Group II appears to be mainly affected by the slowness of information processing.

Age-related trends of Stroop-like interference in animal size tests in 5- to 12-year-old children and young adults.

Few studies have examined the development of Prepotent Response Inhibition (Nigg's interference control) from childhood to adulthood. This cross-sectional study examined differences in Prepotent Response Inhibition among children of 5 age groups: twenty 5- to 6-year-olds, twenty-one 7- to 8-year-olds, twenty-two 9- to 10-year-olds, eighteen 11- to 12-year-olds, and 24 young adults (18- to 24-year-olds). Participants were administered two Stroop-like tasks: the Real Animal Size Test described in 2009 by Catale and Meulemans, which requires that participants decide the real size of animals (big vs. small) displayed in a mismatching pictorial size; and the Pictorial Animal Size Test (an original test), which requires that participants report the pictorial size of the animals. Results showed clear differences between the tests. The Pictorial Animal Size Test elicited robust interference whereas the Real Animal Size Test elicited no interference. The Pictorial Animal Size Test also revealed the development of Prepotent Response Inhibition in children of 5-12 years and between children and young adults. These results were discussed with respect to differences in strengths of processing. The Pictorial Animal Size Test can be a useful tool for assessment of Prepotent Response Inhibition in children older than 5 years of age.

Target-to-distractor ratio effects on decision time in the orderly array shape cancellation task.

The cancellation task is a paper-and-pencil test commonly used to assess attention or planning. This study investigated whether the decision time performance on the task was influenced by the number of targets and distractors. This study reduced the demand of planning and used an index of the decision time, an estimate of the time taken to decide whether to mark a stimulus. Forty healthy adults (M age = 21.3 yr., SD = 1.5) performed five cancellation tasks. Four tasks were conducted with instructions to mark a detected target. The target-to-distractor ratio varied from 35/15, 40/10, 45/5, and 50/0, and one task with instructions to mark all stimuli (50/0), to measure the motor time to mark targets. One-way analysis of variance indicated statistically significant differences between conditions. There was a linear relationship between decision time and target-to-distractor ratio; the decision time increased as the proportion of distractors increased. The results suggested the decision time reflects the frequency of switches between responses to targets and distractors or attention modulation of processing to targets and distractors.

Temporal and spatial parameters of stepping in place in children and adults.

Characteristics of synchronized and self-paced stepping in place were examined by analyzing a temporal parameter (step frequency) and a spatial parameter (step height). Participants were 20 adults (10 women, 10 men; M age = 22.5 yr., range = 21-23) and 10 children (5 girls, 5 boys; M age=6.1 yr., range = 5-6). Results indicated that: (1) the step frequencies, which were equivalent for both groups, were well coincident with stimulus frequencies; (2) when step frequencies were imposed, the step height decreased with increasing step frequency, except for the lowest frequency condition in children; (3) movement consistency was the highest at 2 Hz and deteriorated if the step frequency was higher or lower; and (4) the self-paced stepping in place was optimal in terms of movement consistency. These results showed that stepping in place is a rhythmic movement at a given range of frequency which is coordinated so as to keep the product of step frequency and step height constant.

Effects of age, intelligence and executive control function on saccadic reaction time in persons with intellectual disabilities.

The current research aimed to clarify the influence of age, intelligence and executive control function on the central tendency and intraindividual variability of saccadic reaction time in persons with intellectual disabilities. Participants were 44 persons with intellectual disabilities aged between 13 and 57 years whose IQs were between 14 and 70. Executive control function was evaluated by a test of sustained simple motor action. To elicit saccades, a predictive visually guided saccade paradigm was used. Intelligence and executive control function were significantly associated with saccadic reaction time. The central tendency of saccadic reaction time was negatively correlated with intelligence. The more serious the degree of executive control dysfunction was, the larger the intraindividual variability of saccadic reaction time. It is thought that intelligence and executive control function have relatively independent influences on saccadic reaction time. However, there is a possibility that the increase of intraindividual variability in saccadic reaction time due to the problem of executive control function extends the central tendency of saccadic reaction time.

Age-related trends of interference control in school-age children and young adults in the Stroop color-word test.

In this cross-sectional study, differences in interference control, one component of executive function, were investigated among three age groups, 15 early childhood (7- to 8-yr.-olds), 25 middle childhood (9- to 12-yr.-olds), and 20 young adults (21- to 30-yr.-olds). Participants were administered a computer version of the Stroop color-word test with an oral response; correct responses, response time (RT), and the interference ratio were examined. The data indicated that (1) most of the participants showed no errors in word reading, color-naming, and incongruent color-naming tasks; (2) in word-reading and color-naming tasks, RT for 7- to 8-yr.-olds was longer than that for 9- to 12-yr.-olds, while RT of 9- to 12-yr.-olds and young adults were comparable; (3) in an incongruent color-naming task, RT for 7- to 8-yr.-olds was longer than RT for 9- to 12-yr.-olds, which was longer than RT for young adults; and (4) the interference ratio was higher in 7- to 8-yr.-olds than in 9- to 12-yr.-olds, which was higher than in young adults. These results suggested the difference in interference control between early and middle childhood reported on the go/no-go task and the stop-signal procedure would be observed in the Stroop color-word paradigm as well. The utility of this modified Stroop color-word test for those with intellectual and developmental disabilities was discussed.

Features of Stroop and reverse-Stroop interference: analysis by response modality and evaluation.

Stroop interference (the Stroop effect) is the phenomenon observed when naming the color of an incongruent stimulus, such as the word "red" printed in blue ink; typically, this color incongruence causes slower naming compared to a neutral stimulus, such as a blue square patch. Reverse-Stroop interference occurs when reading the stimulus takes longer than reading the neutral stimulus. Features of Stroop and reverse-Stroop interference were examined, focusing on the difference between the response modalities--oral response and manual response--and the difference between methods of evaluating performance (time or correct responses) and the interference score. Participants were 47 students (30 women, 17 men; M age=20.8 yr., range=19-29). The results were as follows: (1) the performance of the reverse-Stroop condition was higher than that of the Stroop condition for both oral and manual responses; (2) the Stroop interference score was significantly greater with the oral response than with the manual response; and (3) the reverse-Stroop interference score was constant regardless of the response modality. The results were discussed with respect to differences in processing speeds of verbal and sensory information.

Verbal regulation of grip force in preschoolers.

The purpose of this study was to clarify the developmental processes in verbal regulation by preschool children. Participants were 152 typically developing children (74 boys, 78 girls) between 4 and 6 years of age (M = 5.3, SD = .8), and 30 healthy adults (15 men, 15 women) between 19 and 26 years of age (M = 20.8, SD = 1.4). In Exp. 1, the task was to regulate grip force based on quantitative instruction which implies using a scale for regulation. Participants were required to produce a half-grip force of the maximum (Task 1). In Exp. 2, the task was grip-force regulation based on nonquantitative instruction. The participants were asked to respond with a slightly weaker grip force than the maximum (Task 2) and then a further weaker grip force (Task 3) than that used on Task 2. The regulation rates produced the extent of regulation and suggest regulation by quantitative instruction may develop earlier than by nonquantitative instruction. Also, precise grip-force regulation based on the semantic aspect of instruction may be difficult for young children. The developmental changes in the rate of performance especially observed in children of 4 to 6 years indicate that the tendency to use too much grip force disappears during this preschool period. In addition, too little grip force in regulation may reflect the developmental process toward fine grasping movements.