Brief report: Response inhibition and processing speed in children with motor difficulties and developmental coordination disorder

A previous study reported that children with poor motor skills, classified as having motor difficulties (MD) or Developmental Coordination Disorder (DCD), produced more errors in a motor response inhibition task compared to typically developing (TD) children but did not differ in verbal inhibition errors. The present study investigated whether these groups differed in the length of time they took to respond in order to achieve these levels of accuracy, and whether any differences in response speed could be explained by generally slow information processing in children with poor motor skills. Timing data from the Verbal Inhibition Motor Inhibition test were analyzed to identify differences in performance between the groups on verbal and motor inhibition, as well as on processing speed measures from standardized batteries. Although children with MD and DCD produced more errors in the motor inhibition task than TD children, the current analyses found that they did not take longer to complete the task. Children with DCD were slower at inhibiting verbal responses than TD children, while the MD group seemed to perform at an intermediate level between the other groups in terms of verbal inhibition speed. Slow processing speed did not account for these group differences. Results extended previous research into response inhibition in children with poor motor skills by explicitly comparing motor and verbal responses, and suggesting that slow performance, even when accurate, may be attributable to an inefficient way of inhibiting responses, rather than slow information processing speed per se.     

The link between motor impairment level and motor imagery ability in children with developmental coordination disorder

The present study examined motor imagery ability in children with developmental coordination disorder (DCD). Specifically, it explored whether children with varying degrees of motor impairment differed in their ability to perform motor imagery tasks. Fourty-two children scoring below the 15th percentile on the Movement ABC were split into two groups--DCD severe (DCD-S), scoring on or below the 5th percentile, and DCD mild (DCD-M), scoring from the 6th to 15th percentiles--and compared to 21 age matched controls. Participants performed two motor imagery tasks--hand (performed without and with specific imagery instructions) and whole-body rotation. The results demonstrated that children in the DCD-S group had a generalized motor imagery deficit in that they were less accurate across tasks than controls (and the DCD-M group on the hand task) and showed little benefit when given specific imagery instructions. The DCD-M group appeared capable of performing simpler motor imagery transformations, but were less successful as task complexity increased. Unlike the DCD-S group, the DCD-M group did show some benefit from specific imagery instructions with increases in accuracy on the hand task. These results suggest that a motor imagery deficit does exist in many children with DCD but that its presentation can vary--factors such as the individual child's level of motor impairment and task complexity appear to be linked to the profile of deficits observed, which could explain the inconsistent findings of previous studies. Although this study lends support to the theory that a deficit in internal modeling is an underlying problem for children with DCD, still more research is required to develop the theory further.     

Speed of processing within semantic memory following severe closed head injury.

This study investigated the effects of severe closed head injury (CHI) on the speed of information processing within semantic categories. The question of whether subjects were able to benefit from priming was also investigated. Survivors of severe CHI who were less than 1 year postinjury and survivors who were greater than 1 year postinjury were compared with neurologically normal matched controls utilizing a category judgement task. The results demonstrated slower processing within semantic memory for both groups of CHI patients compared to normal controls. Furthermore, individuals with CHI were able to benefit from priming to the same relative degree as control subjects. Overall, the results suggested semantic organization remains intact after severe CHI, but accessing semantic information is slowed.     

Discourse after Closed Head Injury in Young Children

This study examined narrative discourse in 23 children, ages 6 to 8 years, who sustained a severe closed head injury (CHI) at least 1 year prior to assessment. Narratives were analyzed at multiple levels using language and information structure measures. Results revealed significant discourse impairments in the CHI group on all measures of information structure, whereas differences in the linguistic domain failed to reach significance. In addition, effects of age at injury and lateralization of lesion on discourse were considered. Although no significant differences were found according to age at injury, a consistent pattern of generally poorer discourse scores was found for the early injured group (<5 years). With regard to lesion focus, the group findings were unimpressive. However, preliminary examination of individual CHI cases with relatively large lateralized lesions suggested that the late injured children may show the language–brain patterns reported in brain-injured adults, whereas early injured children may not.     

Recovery in Memory Function,and its Relationship to Academic Success,at 24 Months Following Pediatric TBI*

While a number of research papers have reported findings on memory deficits following traumatic brain injury (TBI), only limited studies have monitored the recovery of these skills over time. The present study examined memory ability and its effect on academic success in a group of children who had sustained a mild, moderate, or severe traumatic brain injury (TBI). Results showed that the severe TBI group exhibited greater deficits on memory tasks, irrespective of modality, in the acute, 6-, 12-, and 24-month postinjury stages, in comparison to mild and moderate TBI groups. Performance on academic measures was dependent on both injury severity and task demands. Preinjury academic ability and verbal memory indices best predicted academic success.     

Recovery in memory function, and its relationship to academic success, at 24 months following pediatric TBI.

While a number of research papers have reported findings on memory deficits following traumatic brain injury (TBI), only limited studies have monitored the recovery of these skills over time. The present study examined memory ability and its effect on academic success in a group of children who had sustained a mild, moderate, or severe traumatic brain injury (TBI). Results showed that the severe TBI group exhibited greater deficits on memory tasks, irrespective of modality, in the acute, 6-, 12-, and 24-month postinjury stages, in comparison to mild and moderate TBI groups. Performance on academic measures was dependent on both injury severity and task demands. Preinjury academic ability and verbal memory indices best predicted academic success.     

Cognitive Effects of HIV-1 Infection

The major neurological complication of human immunodeficiency virus type 1 (HIV-1) infection is cognitive impairment, which can range in severity from a mild subclinical cognitive inefficiency to a severe dementing illness. Mild to moderate cognitive impairment is identified primarily by neuropsychological tests. The prevalence and severity of cognitive impairment associated with HIV-1 infection increases as the disease progresses. Deficits in attention, information processing speed, memory, and motor abilities can occur early in the course of HIV-1 infection, with deficits in abstraction and executive functions observed in later stages of infection. The nature of the cognitive impairment observed is thought to reflect the effects of HIV-1 infection on the integrity of subcortical or frontostriatal brain systems. Issues related to the detection of subclinical to severe cognitive impairment are discussed, along with the clinical significance of mild cognitive impairment as a significant risk factor for mortality in HIV-1 infection. The need to control for possible confounding factors that can influence test performance is also reviewed.     

Divided attention years after severe closed head injury: the effect of dependencies between the subtasks

Lesions of white matter which connects distant brain areas are characteristic for closed head injury (CHI). It was predicted that this impairs divided attention only if dependent subtasks are used which require communication between corresponding brain processes. Fourteen chronic severe CHI patients (mean age 42 years) and 14 healthy controls, matched on age, gender, and education, participated in an experiment on divided attention. A typical left hemisphere task and a typical right hemisphere task must be simultaneously performed in a condition where they are completely independent and in conditions with dependencies between the tasks. Only in the dependent conditions the CHI group showed poor divided attention performance.     

Understanding of literal truth, ironic criticism, and deceptive praise following childhood head injury.

Children with closed head injury (CHI) have semantic-pragmatic language problems that include difficulty in understanding and producing both literal and nonliteral statements. For example, they are relatively insensitive to some of the social messages in nonstandard communication as well as to words that code distinctions among mental states. This suggests that they may have difficulty with comprehension tasks involving first- and second-order intentionality, such as those involved in understanding irony and deception. We studied how 6- to 15-year-old children, typically developing or with CHI, interpret scenarios involving literal truth, ironic criticism, and deceptive praise. Children with severe CHI had overall poorer mastery of the task. Even mild CHI impaired the ability to understand the intentionality underlying deceptive praise. CHI, especially biologically significant CHI, appears to place children at risk for failure to understand language as externalized thought.     

The development of verbal and visual working memory processes: a latent variable approach

Working memory (WM) processing in children has been studied with different approaches, focusing on either the organizational structure of WM processing during development (factor analytic) or the influence of different task conditions on WM processing (experimental). The current study combined both approaches, aiming to distinguish verbal and visual processing in order to investigate WM development. We investigated recall performance under different task conditions in a sample of 5- to 13-year-olds, applying latent class regression analysis. In this analysis, we examined latent classes (subgroups) within the sample that differed in terms of processing type. The interpretations of the latent classes were validated internally using characteristics of the latent classes and externally using recall performance of words and figures. The results showed that children of different developmental stages used the same type of processing under the same conditions. However, due to developmental differences, their overall performances differed, showing groups of children who were successful in verbal or visual processing and groups of children who were not. This study shows and discusses the importance of disentangling the influence of task conditions from the influence of WM development when interpreting recall performance in children.     

A comparison of characteristics,developmental disorders and motor progression between children with and without developmental coordination disorder

Background and aimChildren with Developmental Coordination Disorder (DCD) have difficulty in the development of motor coordination and with learning new motor skills. Studies demonstrate that children with DCD differ in terms of the nature and severity of their motor difficulties, the incidence of co occurring conditions and family background. However, little is known whether these profiles may relate to motor progression over time. The aim of this study was to describe the profiles of children with and without DCD and track motor progression over time.MethodThe characteristics of thirty-four 7–14 year old children (M = 10.07, 85.3% boys) with and without DCD were compared and their motor progression monitored over a two academic years. DCD was identified using DSM5 criteria. The Movement Assessment Battery for Children-2 (MABC-2) was used to classify children as TD (≥25th percentile), having moderate motor coordination difficulties (6-16th percentile) or severe motor coordination difficulties (≤ 5th percentile). The Kaufman Brief Intelligence Test – 2 (KBIT-2) was used to measure full scale IQ. Parent questionnaires were used to gather information on socio economic status and co occurrence of other developmental disorders. We used ANOVA to assess whether there were differences in characteristics between the TD children, children with severe motor coordination difficulties and children with moderate motor coordination difficulties. Linear mixed effect modelling was used to estimate any change in motor performance over time and whether this differed between the three groups of children.ResultsChildren with severe motor coordination difficulties had distinct profiles in motor and non-motor domains, lower IQ and a greater likelihood of having associated characteristics of 2 or more developmental disorders. We found significant differences between the poor motor performance of the severe group compared to the other two groups. Longitudinal analyses revealed stable, persistent and lower motor competence for the severe group. The rate of change in motor proficiency for the typical and severe groups was similar. However, the group with moderate motor difficulties gained on average more points per week compared to the typical group and achieved motor scores in the typically developing range over time.ConclusionsThis is one of the first studies to compare the characteristics and rate of motor progression of children with and without DCD using different motor proficiency cut off scores. The children with severe motor coordination difficulties progressed at the same rate as typically developing peers but remained in the severe group over time, whereas the children with moderate motor coordination difficulties caught up to TDC. The results indicate that different intervention may be required according to the nature and severity of the characteristics in both the motor and non-motor domains of children with DCD.     

Defective number module or impaired access? Numerical magnitude processing in first graders with mathematical difficulties

This study examined numerical magnitude processing in first graders with severe and mild forms of mathematical difficulties, children with mathematics learning disabilities (MLD) and children with low achievement (LA) in mathematics, respectively. In total, 20 children with MLD, 21 children with LA, and 41 regular achievers completed a numerical magnitude comparison task and an approximate addition task, which were presented in a symbolic and a nonsymbolic (dot arrays) format. Children with MLD and LA were impaired on tasks that involved the access of numerical magnitude information from symbolic representations, with the LA children showing a less severe performance pattern than children with MLD. They showed no deficits in accessing magnitude from underlying nonsymbolic magnitude representations. Our findings indicate that this performance pattern occurs in children from first grade onward and generalizes beyond numerical magnitude comparison tasks. These findings shed light on the types of intervention that may help children who struggle with learning mathematics.     

Verbal fluency over time as a measure of automatic and controlled processing in children with ADHD

The performance of ADHD children on semantic category fluency (SCF) versus initial letter fluency (ILF) tasks was examined. For each participant, word production was recorded for each 15-s time slice on each task. Performance on both fluency tasks was compared to test the hypothesis that children with ADHD are characterized by a performance deficit on the ILF task because performance on this task is less automated than performance on the SCF. Children classified with ADHD (N = 20) were compared to children with other psychopathology (N = 118) and healthy controls (N = 130). Results indicated that the groups could not be differentiated by the total number of words produced in 60 s in either fluency task. As hypothesized, a significant interaction of group by productivity over time by type of fluency task was found: ADHD children had more problems finding words in the first 15 s of the IFL than did children in the other two groups, and as compared with their performance on the SCF. Results were taken to indicate that children with ADHD symptoms show a delay in the development of automating skills for processing abstract verbal information.     

A Developmental Explanation For Children’s Motor behavior

Two experiments were conducted to test the application of Pascual-Leone’s (1970) neo-Piagetian theory for explaining children’s acquisition of skill in a curvilinear positioning task. Two groups of children (late pre-operational 6 yr olds and early concrete 8 yr olds) were identified and from each group 10 low M-processors and 10 high M-processors were selected (total n=40) through use of the Children’s Embedded Figures Test. The 6 yr olds were administered 2-and 3-scheme curvilinear positioning tasks while the 8 yr olds performed 3-and 4-scheme tasks. The difference between the two experiments was the nature of the positioning tasks, i.e., one task allowed visual processing of information, while the other did not. Both experiments supported the neo-Piagetian predictions of structural mental space as explaining the developmental nature of motor skill acquisition, and functional mental space as explaining individual differences within stages in children’s performance.     

Assessment of visual-spatial deficits in patients with Parkinson's disease and closed head injuries using virtual environments.

Cognitive spatial deficits have been reliably reported in patients with Closed Head Injury (CHI), though in patients with Parkinson's disease (PD) the phenomenon is disputed. CHI and non-demented PD patients were tested using a Judgement of Line Orientation Test, and two spatial tests using virtual environments (VEs). Performance on the Line Orientation and one VE test was worse in the CHI group than controls, but PD patients showed no apparent spatial deficits. However, performance on the second VE test (virtual tray of objects task) did reveal a deficit, both CHI and PD groups being significantly impaired. The data illustrate that particular spatial deficits can be differentiated using appropriate VE-based tasks, and that non-demented PD patients show a paradigm-specific visual-spatial impairment.     

Attentional skills in the acute phase following pediatric traumatic brain injury.

Only a limited number of studies have investigated attention following pediatric head-injury. The present study examined sustained attention and processing speed in a group of children who had sustained a mild (n = 27), moderate (n = 33) or severe (n = 16) traumatic brain injury (TBI). No significant differences were evident between the TBI groups on reaction time measures. Results did show that the severe TBI group exhibited greater deficits in the area of sustained attention, in comparison to children with mild and moderate injuries, in the acute stage following traumatic brain injury. This difficulty may impact on the future development of skills dependent on intact attentional capacity.     

Impaired skill learning in patients with severe closed-head injury as demonstrated by the serial reaction time (SRT) task

A group of 20 patients who sustained closed-head injury (CHI) and a matched control group of 20 individuals were tested on the serial reaction time (SRT) task. Three different sequence-learning measures were generated from the task: two implicit and one explicit. The two implicit sequence-learning measures include: (1) the learning rate on the first five blocks of the repeated sequence, assumed to reflect primarily general reaction time learning, and (2) the difference between the fifth block of the repeated sequence and the sixth block, a random sequence that reflects implicit sequence-specific learning. In addition, an explicit measure of sequence learning was generated. The results indicate that the CHI group was impaired on the explicit measure of sequence learning. The groups did not differ on general reaction time learning, one of the implicit measures of sequence learning. However, the control group was superior to the CHI group in learning the specific sequence repeated in the SRT task. This pattern of results is unique to the CHI group, corresponding with neither that of amnesic patients nor with that of patients with dysfunction of the basal ganglia (i.e., Parkinson's diseases).     

Attentional Skills in the Acute Phase Following Pediatric Traumatic Brain Injury

Only a limited number of studies have investigated attention following pediatric head-injury. The present study examined sustained attention and processing speed in a group of children who had sustained a mild (n = 27), moderate (n = 33) or severe (n = 16) traumatic brain injury (TBI). No significant differences were evident between the TBI groups on reaction time measures. Results did show that the severe TBI group exhibited greater deficits in the area of sustained attention, in comparison to children with mild and moderate injuries, in the acute stage following traumatic brain injury. This difficulty may impact on the future development of skills dependent on intact attentional capacity.     

Attentional processes in young children with congenital visual impairment

The study investigated attentional processes of 32 preschool children with congenital visual impairment (VI). Children with profound visual impairment (PVI) and severe visual impairment (SVI) were compared to a group of typically developing sighted children in their ability to respond to adult directed attention in terms of establishing, maintaining, and shifting attention on toys. The measures of children's sensory‐motor understanding (SMU) and language ability were obtained using the Reynell‐Zinkin scales of mental development. The video‐recordings of these play‐based assessments were coded for three categories of behavioural responses (Establish, Maintain, and Shift). The three groups were matched on verbal comprehension (VC), but differed significantly in their SMU and their chronological age. The groups of children with PVI and SVI were found to be comparable in their ability to establish and maintain attention on objects. Despite a relatively good performance overall both groups scored significantly lower on those skills than children who were sighted. However, with regards to attention shifting, children with PVI showed significantly lower performance than both the children with SVI and the sighted children who were similar on this component. Ability to maintain and shift attention was significantly related to the cognitive ability of children with PVI; however the poorer attentional responses were not confined only to the children with low IQ. The results are discussed in relation to the role of vision, cognitive ability and executive function in attentional processes in children with congenital VI.     

Multi-limb coordination and rhythmic variability under varying sensory availability conditions in children with DCD

Children with Developmental Coordination Disorder (DCD) have sensory processing deficits; how do these influence the interface between sensory input and motor performance? Previously, we found that children with DCD were less able to organize and maintain a gross motor coordination task in time to an auditory cue, particularly at higher frequencies [Whitall, J., Getchell, N., McMenamin, S., Horn, C., Wilms-Floet, A., & Clark, J. (2006). Perception-action coupling in children with and without DCD: Frequency locking between task relevant auditory signals and motor responses in a dual motor task. Child: Care, Health, and Development, 32, 679-692]. In the present study, we examine the same task (clapping in-phase to marching on a platform) under conditions involving the removal of vision and hearing. Eleven children with DCD (mean=7.21, SD=0.52 years), 7 typically developing (TD) children (mean=6.95+/-0.72 years), and 10 adults performed continuous clapping while marching under four conditions: with vision and hearing, without vision, without hearing, and without both. Results showed no significant condition effects for any measure taken. The DCD group was more variable in phasing their claps and footfalls than both the adult group and the TD group. There were also significant group effects for inter-clap interval coefficient of variation and inter-footfall interval coefficient of variation, with the DCD group being the most variable for both measures. Coherence analysis between limb combinations (e.g., left arm-right arm, right arm-left leg) revealed that the adults exhibited significantly greater coherence for each combination than both of the children's groups. The TD group showed significantly greater coherence than the DCD group for every limb combination except foot-foot and left hand-right foot. Measures of approximate entropy indicated that adults differed from children both with and without DCD in the structure of the variability across a trial with adults showing more complexity. Children with DCD are able to accomplish a self-initiated gross-motor coordination task but with increased variability for most but not all measures compared to typically developing children. The availability of visual and/or auditory information does not play a significant role in stabilizing temporal coordination of this task, suggesting that these are not salient sources of information for this particular task.