Arm movement control: differences between children with and without attention deficit hyperactivity disorder

Determining the optimal challenge point for learning motor skills in children with attention deficit/hyperactivity disorder

The purpose of this study was to investigate the optimal challenge point for learning motor skills in children with and without attention deficit/hyperactivity disorder (ADHD). Ninety-six 9- to 10-year-old children, including 48 children with ADHD and 48 neurotypical children, were randomly assigned to one of four practice groups with varying levels of nominal and functional task difficulty. They performed 63 trials of a dart throwing task in the acquisition phase and 18 trials in the retention and transfer tests a day later. The results showed that neurotypical children outperformed children with ADHD in all phases of the study. Both groups improved in the acquisition phase and performed better in the retention and transfer tests. Interestingly, low nominal task difficulty was associated with better learning for both groups, despite lower average performance for children with ADHD. Thus, despite their performance differences, we did not find a difference in the effective challenge point between children with ADHD and their neurotypical peers.

Identifying activity level related movement features of children with ASD based on ADOS videos

Autism spectrum disorder (ASD) is a neurodevelopmental disorder that affects about 2% of children. Due to the shortage of clinicians, there is an urgent demand for a convenient and effective tool based on regular videos to assess the symptom. Computer-aided technologies have become widely used in clinical diagnosis, simplifying the diagnosis process while saving time and standardizing the procedure. In this study, we proposed a computer vision-based motion trajectory detection approach assisted with machine learning techniques, facilitating an objective and effective way to extract participants' movement features (MFs) to identify and evaluate children's activity levels that correspond to clinicians' professional ratings. The designed technique includes two key parts: (1) Extracting MFs of participants' different body key points in various activities segmented from autism diagnostic observation schedule (ADOS) videos, and (2) Identifying the most relevant MFs through established correlations with existing data sets of participants' activity level scores evaluated by clinicians. The research investigated two types of MFs, i.e., pixel distance (PD) and instantaneous pixel velocity (IPV), three participants' body key points, i.e., neck, right wrist, and middle hip, and five activities, including Table-play, Birthday-party, Joint-attention, Balloon-play, and Bubble-play segmented from ADOS videos. Among different combinations, the high correlations with the activity level scores evaluated by the clinicians (greater than 0.6 with p < 0.001) were found in Table-play activity for both the PD-based MFs of all three studied key points and the IPV-based MFs of the right wrist key point. These MFs were identified as the most relevant ones that could be utilized as an auxiliary means for automating the evaluation of activity levels in the ASD assessment.

Source Localization of Somatosensory Neural Generators in Adults with Attention-Deficit/Hyperactivity Disorder

Attention-Deficit/Hyperactivity Disorder (ADHD) is a neurodevelopmental disorder, where differences are often present relating to the performance of motor skills. Our previous work elucidated unique event-related potential patterns of neural activity in those with ADHD when performing visuomotor and force-matching motor paradigms. The purpose of the current study was to identify whether there were unique neural sources related to somatosensory function and motor performance in those with ADHD. Source localization (sLORETA) software identified areas where neural activity differed between those with ADHD and neurotypical controls when performing a visuomotor tracing task and force-matching task. Median nerve somatosensory evoked potentials (SEPs) were elicited, while whole-head electroencephalography (EEG) was performed. sLORETA localized greater neural activity post-FMT in those with ADHD, when compared with their baseline activity (p < 0.05). Specifically, greater activity was exhibited in BA 31, precuneus, parietal lobe (MNI coordinates: X = -5, Y = -75, and Z = 20) at 156 ms post stimulation. No significant differences were found for any other comparisons. Increased activity within BA 31 in those with ADHD at post-FMT measures may reflect increased activation within the default mode network (DMN) or attentional changes, suggesting a unique neural response to the sensory processing of force and proprioceptive afferent input in those with ADHD when performing motor skills. This may have important functional implications for motor tasks dependent on similar proprioceptive afferent input.

How effective is fine motor training in children with ADHD? A scoping review

Background

Motor deficiencies are observed in a large number of children with ADHD. Especially fine motor impairments can lead to academic underachievement, low self-esteem and frustration in affected children. Despite these far-reaching consequences, fine motor deficiencies have remained widely undertreated in the ADHD population. The aim of this review was to systematically map the evidence on existing training programs for remediating fine motor impairments in children with ADHD and to assess their effectiveness.

Methods

The scoping review followed the PRISMA-ScR guidelines. In March 2020, PsycINFO, MEDLINE (PubMed), Web of Science, Google Scholar and The Cochrane Database of Systematic Reviews were searched for evidence. The eligibility criteria and the data charting process followed the PICO framework, complemented by study design. The investigated population included children with a formal ADHD diagnosis (either subtype) or elevated ADHD symptoms aged between 4 and 12 years, both on and off medication. All training interventions aiming at improving fine motor skills, having a fine motor component or fine motor improvements as a secondary outcome were assessed for eligibility; no comparators were specified.

Results

Twelve articles were included in the final report, comprising observational and experimental studies as well as a review. Both offline and online or virtual training interventions were reported, often accompanied by physical activity and supplemented by training sessions at home. The training programs varied in length and intensity, but generally comprised several weeks and single or multiple training sessions per week. All interventions including more than one session were effective in the treatment of fine motor deficiencies in children with ADHD and had a wide range of additional positive outcomes. The effects could be maintained at follow-up.

Conclusions

Fine motor training in children with ADHD can be very effective and multiple approaches including specific fine motor and cognitive training components, some kind of physical activity, feedback mechanisms, or multimodal treatments can be successful. Training programs need to be tailored to the specific characteristics of the ADHD population. A mHealth approach using serious games could be promising in this context due to its strong motivational components.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12887-021-02916-5.

Cortico-basal ganglia circuits underlying dysfunctional control of motor behaviors in neuropsychiatric disorders

Neuropsychiatric disorders often manifest with abnormal control of motor behavior. Common symptoms include restricted and repetitive patterns of behavior (RRBs). Cortico-basal ganglia circuits have been implicated in the etiology of RBBs. However, there is a vast range of behaviors encompassed in RRBs, from simple explosive motor tics to rather complex ritualized compulsions. In this review, we highlight how recent findings about the function of specific basal ganglia circuits can begin to shed light into defined motor symptoms associated with neuropsychiatric disorders. We discuss recent studies using genetic animal models that advocate that different aspects of motor repetition in neurodevelopmental disorders, like obsessive-compulsive disorder and autism spectrum disorder, emerge from particular dysregulations in distinct cortico-basal ganglia circuits.

Kinematic analysis of fast pen strokes in children with ADHD

In this study, we aimed to determine whether a new measure of fine motor skills, the Pen Stroke Test (PST), can discriminate between children with and without attention-deficit/hyperactivity disorder (ADHD). Twelve children with ADHD and 12 controls age 8-11 were asked to produce handwriting strokes on a digitizer. The sigma-lognormal model derived from the Kinematic Theory of rapid human movements was used to analyze the strokes. Standard measurements of fine motor skills and handwriting were also obtained. Children with ADHD demonstrated poorer motor planning (t₀, D) and execution (nbLog) and greater variability in motor control (SNR/nbLog) than did controls. Parameters extracted from the PST were significantly correlated with performance on other motor and handwriting measures. This study provides preliminary evidence that the PST may be useful as a tool for rapidly detecting motor skill problems in the context of ADHD.

Cognitive predictors of sequential motor impairments in children with dyslexia and/or attention deficit/hyperactivity disorder

This study examined cognitive predictors of sequential motor skills in 215 children with dyslexia and/or attention deficit/hyperactivity disorder (ADHD). Visual working memory and math fluency abilities contributed significantly to performance of sequential motor abilities in children with dyslexia (N = 67), ADHD (N = 66) and those with a comorbid diagnosis (N = 82), generally without differentiation between groups. In addition, primary diagnostic features of each disorder, such as reading and inattention, did not contribute to the variance in motor skill performance of these children. The results support a unifying framework of motor impairment in children with neurodevelopmental disorders such as dyslexia and ADHD.

Fine motor ability and psychiatric disorders in youth

Impaired fine motor ability has been linked to several domains of psychopathology. However, studies validating the specificity of this association among several categorical psychiatric disorders are still needed. The aim of this study was to assess differences in fine motor ability performance among four non-overlapping groups of psychiatric disorders and a group of typical developing comparisons (TDC). Our sample consisted of 2035 subjects aged 6-14-year-old. Diagnoses of psychiatric disorders were performed with the Development and Well-Being Assessment (DAWBA). Five non-overlapping groups without comorbidity were formed: phobic disorders (n = 101), distress disorders (n = 82), attention deficit hyperactivity disorder (ADHD) (n = 133), oppositional defiant disorder/conduct disorder (ODD/CD) (n = 52) and one group of typical developing comparisons (TDC) (n = 1667). Fine motor ability was evaluated by three tasks: sequential finger-thumb opposition, Oseretsky, and pronation/supination tests. Each task was assessed by total time to perform the movement and levels of accuracy, fluency, symmetry, precision, and coordination. We found that, when compared to TDC, the ADHD group performed more poorly in total fine motor ability (mean difference = - 0.28; p = 0.014), time to complete the task (mean difference = 0.36; p < 0.001), accuracy (mean difference = - 0.30; p = 0.005), fluency (mean difference = - 0.26; p = 0.03), symmetry (mean difference - 0.25; p = 0.04), precision (mean difference = - 0.26; p = 0.026), and coordination (mean difference = - 0.25; p = 0.042). The ADHD group also took more time to complete the task than the ODD/CD group (mean difference = 0.45; p = 0.037). No other significant between-group differences were found. Additional analyses showed those differences were statistically significant for all ADHD dimensions. Our results suggest that children with ADHD present impairments in all aspects of fine motor abilities compared to TDC, a difference not found in other psychiatric disorders.

Knowledge of performance feedback among boys with ADHD

BACKGROUND

Children with attention deficit-hyperactivity disorder (ADHD) often experience delays in acquiring competence completing fundamental motor skills. The effects of augmented prescriptive knowledge of performance feedback (PKP) have not been explored as a possible component solution.

AIMS

The purpose of this study was to test the motor learning effects of KP among boys with ADHD.

METHODS AND PROCEDURES

Thirty-one boys with ADHD, randomly selected into either a treatment or a control group, completed a series of cornhole games. It was hypothesized that PKP feedback administered to treatment group participants would increase motor learning. Dependent variables included cornhole scores and quality of performance measures.

OUTCOMES AND RESULTS

Both groups improved in cornhole scores and improvement was not dependent upon KP. Treatment group participants performed significantly better in quality of performance of the underhand toss compared to the control group.

CONCLUSIONS AND IMPLICATIONS

PKP feedback improves motor skill performance learning among children with ADHD above knowledge of results feedback only. Recreational program directors should consider using KP feedback when teaching motor skills to boys with ADHD.

Developmental implications of children's brain networks and learning

The human brain works as a synergistic system where information exchanges between functional neuronal networks. Rudimentary networks are observed in the brain during infancy. In recent years, the question of how functional networks develop and mature in children has been a hotly discussed topic. In this review, we examined the developmental characteristics of functional networks and the impacts of skill training on children's brains. We first focused on the general rules of brain network development and on the typical and atypical development of children's brain networks. After that, we highlighted the essentials of neural plasticity and the effects of learning on brain network development. We also discussed two important theoretical and practical concerns in brain network training. Finally, we concluded by presenting the significance of network training in typically and atypically developed brains.

Evidence for deficient motor planning in ADHD

We compare motor planning mechanisms of ADHD and control subjects based on their effect on later observed kinematic characteristics. We monitor hand movement following planning conditions that differ in preparation time, and evaluate the differences across conditions and participants with/without ADHD. Our findings show that when there is sufficient planning time, people without ADHD seem to have a motor plan ready, and immediately initiate a planned movement after a ‘GO’ cue, with a bell shaped velocity profile. When planning time is not sufficient, they start the movement in a delayed time, possibly indicating that they needed to complete a movement plan. However, people with ADHD, did not start movement immediately after the cue, even when provided with a long preparation time, possibly indicating that even for this planning interval they did not have a motion plan ready. The movement was not only delayed, its velocity profile was not bell shaped and had several peaks. We further found differences between control and ADHD participants in the velocity profile, variability and jitter of movements. Our results suggest that ADHD motion characteristics, are associated with an immature motor plan. Based on the results we propose a paradigm to evaluate deficiencies in motor planning.

Shared and differentiated motor skill impairments in children with dyslexia and/or attention deficit disorder: From simple to complex sequential coordination

Dyslexia and Attention deficit disorder (AD) are prevalent neurodevelopmental conditions in children and adolescents. They have high comorbidity rates and have both been associated with motor difficulties. Little is known, however, about what is shared or differentiated in dyslexia and AD in terms of motor abilities. Even when motor skill problems are identified, few studies have used the same measurement tools, resulting in inconstant findings. The present study assessed increasingly complex gross motor skills in children and adolescents with dyslexia, AD, and with both Dyslexia and AD. Our results suggest normal performance on simple motor-speed tests, whereas all three groups share a common impairment on unimanual and bimanual sequential motor tasks. Children in these groups generally improve with practice to the same level as normal subjects, though they make more errors. In addition, children with AD are the most impaired on complex bimanual out-of-phase movements and with manual dexterity. These latter findings are examined in light of the Multiple Deficit Model.

The Effects of Stimulant Medication and Training on Sports Competence Among Children With ADHD

The current study examined the relative efficacy of behavioral sports training, medication, and their combination in improving sports competence among youth with attention deficit/hyperactivity disorder (ADHD). Participants were 73 youth (74% male; 81% Hispanic) between the ages of 5 and 12 diagnosed with Diagnostic and Statistical Manual of Mental Disorders (4th ed.) ADHD enrolled in a Summer Treatment Program (STP). The study consisted of a 2 (medication: methylphenidate, placebo) × 2 (sports training: instruction and practice, recreational play) between-groups design and was conducted over a 3-week period during the STP. Sports training was conducted with a novel sport, badminton, to limit previous sport knowledge and to differentiate it from concurrent sports training that occurred within the STP. Objective and subjective measures of sports skills, knowledge, and behavior were collected. Results indicated that, relative to recreational play, brief sports training improved observed and counselor-rated measures of sports competence including sports skills, knowledge, game awareness, effort, frustration, and enjoyment. During sports training, medication incrementally improved children's observed rule following behavior and counselor-rated sportsmanship relative to placebo. In the absence of sports training, medication improved behavior, effort, and sport knowledge. Training in sports skills and rules produced the largest magnitude effects on sports-related outcomes. Therefore, skills training, rather than medication alone, should be used in conjunction with behavioral intervention to teach sports to youth with ADHD. It is recommended that medication be used only as an adjunct to highly structured sports skills training for youth who display high rates of negative behavior during sports activities.

Components of Motor Deficiencies in ADHD and Possible Interventions

There is a growing body of evidence pointing at several types of motor abnormalities found in attention-deficit/hyperactivity disorder (ADHD). In this article we review findings stemming from different paradigms, and suggest an interweaving approach to the different stages involved in the motor regulation process. We start by reviewing various aspects of motor abnormalities found in ADHD and related brain mechanisms. Then, we classify reported motor impairments associated with ADHD, into four classes of motor stages: Attention to the task, motion preparation, motion execution and motion monitoring. Motor abnormalities and corresponding neural activations are analyzed in the context of each of the four identified motor patterns, along with the interactions among them and with other systems. Given the specifications and models of the role of the four motor impairments in ADHD, we ask what treatments correspond to the identified motor impairments. We analyze therapeutic interventions targeting motor difficulties most commonly experienced among individuals with ADHD; first, Neurofeedback training and EMG-biofeedback. As some of the identified components of attention, planning and monitoring have been shown to be linked to abnormal oscillation patterns in the brain, we examine neurofeedback interventions aimed to address these types of oscillations: Theta/beta frequency training and SCP neurofeedback targeted at elevating the CNV component. Additionally we discuss EMG-Biofeedback interventions targeted at feedback on motor activity. Further we review physical activity and motor interventions aimed at improving motor difficulties, associated with ADHD. These kinds of interventions are shown to be helpful not only in aspects of physical ability, but also in enhancing cognition and executive functioning.

Increased Adaptation Rates and Reduction in Trial-by-Trial Variability in Subjects with Cerebral Palsy Following a Multi-session Locomotor Adaptation Training

Cerebral Palsy (CP) results from an insult to the developing brain and is associated with deficits in locomotor and manual skills and in sensorimotor adaptation. We hypothesized that the poor sensorimotor adaptation in persons with CP is related to their high execution variability and does not reflect a general impairment in adaptation learning. We studied the interaction between performance variability and adaptation deficits using a multi-session locomotor adaptation design in persons with CP. Six adolescents with diplegic CP were exposed, during a period of 15 weeks, to a repeated split-belt treadmill perturbation spread over 30 sessions and were tested again 6 months after the end of training. Compared to age-matched healthy controls, subjects with CP showed poor adaptation and high execution variability in the first exposure to the perturbation. Following training they showed marked reduction in execution variability and an increase in learning rates. The reduction in variability and the improvement in adaptation were highly correlated in the CP group and were retained 6 months after training. Interestingly, despite reducing their variability in the washout phase, subjects with CP did not improve learning rates during washout phases that were introduced only four times during the experiment. Our results suggest that locomotor adaptation in subjects with CP is related to their execution variability. Nevertheless, while variability reduction is generalized to other locomotor contexts, the development of savings requires both reduction in execution variability and multiple exposures to the perturbation.

The consolidation of a motor skill in young adults with ADHD: Shorter practice can be better

Practice on a given sequence of movements can lead to robust procedural memory (skill). In young adults, in addition to gains in performance accrued during practice, speed and accuracy can further improve overnight; the latter, delayed, 'offline', gains are thought to emerge when procedural memory consolidation processes are completed. A recent study suggested that female college students with ADHD show an atypical procedural memory consolidation phase, specifically, gaining speed but losing accuracy, overnight. Here, to test if this accuracy loss reflected a cost of overlong training in adults with ADHD, we compared the performance of female college students with (N=16) and without (N=16) ADHD, both groups given a shorter training protocol (80 rather than the standard 160 task repetitions). Speed and accuracy were recorded before training, immediately after, and at 24-h and 2 weeks post-training. The shortened practice session resulted in as robust within-session gains and additional overnight gains in speed at no costs in accuracy, in both groups. Moreover, individuals with ADHD showed as robust speed gains and retention as in the longer training session, but the costs in accuracy incurred in the latter were eliminated. The shortening of practice sessions may benefit motor skill acquisition in ADHD.

Effects of hippotherapy on brain function, BDNF level, and physical fitness in children with ADHD

[Purpose]

The purpose of this study was to examine the effects of hippotherapy on brain function and levels of blood-derived neurotrophic factor (BDNF) in children with attention deficit and/or hyperactivity disorder (ADHD).

[Methods]

The hippotherapy group (HRG) included twenty children with ADHD and the control group (CG) included 19 children. All participants’ physical fitness, fMRI brain scans, and blood BDNF levels were measured at baseline and after 32 weeks of participating in hippotherapy.

[Results]

After 32 weeks of participating in hippotherapy, the body fat of the HRG was significantly decreased (-1.12 ± 4.20%) and the body fat of the CG was increased (2.38 ± 6.35%) (p=0.049). There was no significant difference of physical fitness in both groups (p>0.05). Although there was a higher decrease in the activated insular area in the HRG (-1.59 ± 0.99) than in the CG (-1.14 ± 1.41), there was no significant difference between the two groups (p>0.05) Also, there was a higher increase in the activated cerebellum area in the HRG (1.97 ± 1.45) than in the CG (1.92 ± 1.81). However, there was no significant difference between the two groups (p>0.05). BDNF levels showed an increased tendency in the HRG (166.29 ± 277.52pg) compared to the CG (21.13 ± 686.33pg); otherwise, there was not any significant difference in these blood levels between the two groups (p>0.05). It can be assumed that big individual differences in the level of ADHD in the study participants might not cause any significant results, although there might be positive changes in the brain function of children with ADHD.

[Conclusion]

Therefore, this study suggests that hippotherapy training would need to be modified and developed to increase the efficacy of hippotherapy in children with ADHD.

What is the evidence of impaired motor skills and motor control among children with attention deficit hyperactivity disorder (ADHD)? Systematic review of the literature

This article presents a review of the studies that have analysed the motor skills of ADHD children without medication and the influence of medication on their motor skills. The following two questions guided the study: What is the evidence of impairment of motor skills and aspects of motor control among children with ADHD aged between 6 and 16 years? What are the effects of ADHD medication on motor skills and motor control? The following keywords were introduced in the main databases: attention disorder and/or ADHD, motor skills and/or handwriting, children, medication. Of the 45 articles retrieved, 30 described motor skills of children with ADHD and 15 articles analysed the influence of ADHD medication on motor skills and motor control. More than half of the children with ADHD have difficulties with gross and fine motor skills. The children with ADHD inattentive subtype seem to present more impairment of fine motor skills, slow reaction time, and online motor control during complex tasks. The proportion of children with ADHD who improved their motor skills to the normal range by using medication varied from 28% to 67% between studies. The children who still show motor deficit while on medication might meet the diagnostic criteria of developmental coordination disorder (DCD). It is important to assess motor skills among children with ADHD because of the risk of reduced participation in activities of daily living that require motor coordination and attention.

The effect of a skipped dose (placebo) of methylphenidate on the learning and retention of a motor skill in adolescents with Attention Deficit Hyperactivity Disorder

Individuals with Attention Deficit Hyperactivity Disorder (ADHD) have difficulties in achieving optimal performance in many everyday and academic tasks, deficits attributed to impaired skill acquisition and procedural memory consolidation. We tested the effect of a skipped dose of methylphenidate (MPH) on learning a movement sequence and its subsequent consolidation into procedural memory in adolescents with ADHD. A crossover double-blind design with placebo was used. Sixteen male adolescents, 16-18 years-old, with ADHD and taking MPH formulations on a daily basis, were trained on performing a 5-element sequence of finger-to-thumb opposition movements. Participants took part in two study conditions, 2 months apart. In each condition a different movement sequence was trained and tested. Participants trained on the task either with active medication or placebo on the day of training, crossed-over between study conditions. Learning effects, speed and accuracy, were assessed within-session, during a 24-h memory consolidation phase. Retention was tested by 2 weeks post-training. There were robust gains in performance both within-session and during the 24-h consolidation phase, in both conditions. However, the discontinuation of MPH on the day of training significantly reduced performance speed, with no loss of accuracy. By 2 weeks, post-training performance was comparable. Adolescents with ADHD who are treated daily but skip a dose of MPH show significant slowing of performance relative to their own performance on medication. However, on a background of daily treatment a skipped dose has no deleterious effect on memory consolidation and retention.

Inhibitory Control Differentiates Rare Target Search Performance in Children

Age-related differences in rare-target search are primarily explained by the speed-accuracy trade-off, primed responses, or decision making. The goal was to examine how motor inhibition influences visual search. Children pressed a key when a rare target was detected. On no-target trials, children withheld reactions. Response time (RT), hits, misses, correct rejection, and false alarms were measured. Tapping tests assessed motor control. Older children tapped faster, were more sensitive to rare targets (higher d'), and reacted more slowly than younger ones. Girls outperformed boys in search sensitivity but not in RT. Motor speed was closely associated with hit rate and RT. Results suggest that development of inhibitory control plays a key role in visual detection. The potential implications for cognitive-motor development and individual differences are discussed.

Atypical acquisition and atypical expression of memory consolidation gains in a motor skill in young female adults with ADHD

Individuals with ADHD often show performance deficits in motor tasks. It is not clear, however, whether this reflects less effective acquisition of skill (procedural knowledge), or deficient consolidation into long-term memory, in ADHD. The aim of the study was to compare the acquisition of skilled motor performance, the expression of delayed--consolidation phase--gains and retention, in persons with and without ADHD. Thirty-two participants, 16 with ADHD, were trained on a sequence of finger movements using a well-established training protocol, and tested before training and immediately, 24h and 2 weeks after training. Both groups showed similar within-session gains in speed; additional, delayed gains were expressed at 24h, but less robustly in ADHD, and at 2 weeks post-training. However, while controls showed significant delayed gains in accuracy at 24h and 2 weeks post-training, accuracy deteriorated in ADHD from pre-training to 24h post-training and was only at pre-training levels by 2-weeks post-training. Our results demonstrate a latent memory consolidation phase in motor sequence learning, expressed as delayed gains in speed and a much delayed recovery of pre-training accuracy, in individuals with ADHD. However, both the acquisition and memory consolidation of motor skills are atypical in ADHD.

Motor function and methylphenidate effect in children with attention deficit hyperactivity disorder

AIM

Hyperactivity, impulsivity and poor attention are the core problems of ADHD and central stimulant medication is the preferred treatment. Many children with ADHD also display motor problems. The present study investigated the presence of motor problems in subjects who showed positive response to central stimulants on ADHD symptoms, compared with non-responders.

METHOD

This is a retrospective study of 73 children diagnosed ADHD, aged 5-17 years, who had been assessed with parts of the 'Motor Function Neurological Assessment' (MFNU) and evaluated with regard to effect of central stimulant medication. The sample was divided into two subgroups based on the responses to methylphenidate: Medicine responders and Non medicine responders.

RESULTS

Stimulant responders showed significantly more motor problems than the non-responders on all sub-tests and on the total problem score of the MFNU. Motor problems were present both in younger (age 5-10 years) and older (11-17 years) stimulant responders. There were no gender differences in motor performance.

CONCLUSION

Our findings indicate that the probability of positive effect of central stimulants on core problems of ADHD is higher when motor problems are present in addition to ADHD symptoms, than when motor problems are absent.

Right-sided spatial difficulties in ADHD demonstrated in continuous movement control

Children with Attention Deficit Hyperactivity Disorder (ADHD) often show spatial attentional deficits, exhibiting a subtle rightwards bias, possibly due to dysfunction within the right hemisphere fronto-parietal network. Approximately 50% of children with ADHD also show signs of movement dysfunction. The nature of this movement dysfunction and possible interactions with spatial attention difficulties has not been clearly described. This study compared 31 children with and 31 children without ADHD on a movement kinematic task that tested hand-drawing movement precision. Participants used an electronic pen on a digitizing tablet. The pen tip position was sampled as X and Y coordinates at 200Hz. The task was to join targets of either 10 or 20mm diameter that were separated by a distance of 62.5 or 125 mm. Constant error in the X and Y planes, peak absolute velocity and acceleration, movement time, the number of pauses and pause time were analysed. Apart from a significantly increased rate of acceleration across all conditions, the children with ADHD demonstrated no temporal difficulties with the task; rather they showed subtle spatial difficulties, possibly suggestive of cerebellar involvement. The children with ADHD showed difficulties in accuracy of movement towards the right. They were less accurate in the X plane when moving towards the right-sided targets over the long distance. Greater variability in target accuracy was shown when moving towards the small target on the right side. The children with ADHD made significantly more pauses on the left target, when preparing the right movement, than the control group. These results suggest that the subtle spatial bias towards the right that has been demonstrated in ADHD in spatial attention also extends into the continuous movement domain.

The Motor Function Neurological Assessment (MFNU) as an indicator of motor function problems in boys with ADHD

BACKGROUND

The paper presents the Motor Function Neurological Assessment (MFNU), as a tool for identifying typical motor function problems in children with Attention Deficit Hyperactivity Disorder (ADHD). The study investigated motor functions in boys diagnosed with Hyperkinetic Disorder (HKD, F.90.0). HKD corresponds to the ADHD-combined (ADHD-C) diagnosis in the DSM-IV. The paper addresses the ability of the instrument to discriminate between non-medicated boys with HKD and a control group consisting of normal non-referred boys without any clinical significant ADHD symptoms.

METHODS

25 drug-naïve boys, aged 8-12 years and recently diagnosed as HKD F90.0, were compared with 27 controls, all boys in the same age range, on 17 MFNU subtests, and with a 'Total score' parameter.

RESULTS

On the individual subtests 80-96% (median 88%) of the ADHD group showed 'moderate' to 'severe' problems, compared to 0-44% (median 14.8%) within the control group. The percentage of 'severe problems' ranged from 44-84%, (median 64%) in the ADHD group, and 0-44% (median 0%) in the control group. The highly significant differences found between the groups on all subtests, and on the Total score scores, indicated that the MFNU had a high discriminative power when children with ADHD and normal controls were compared. The Total score parameter seemed to be a meaningful discriminator of a common underlying factor of the 17 subtests used in the study.

CONCLUSION

The study confirms our clinical findings that the MFNU measures a consistent pattern of motor function problems in children with HKD, and that these problems are rarely represented in individuals without ADHD. Further research is needed to investigate to what extent the MFNU taps motor problems that are truly specific to ADHD, in contrast to motor problems common to children with DCD or other clinical problems.

Response to Brašić (2007): Psychomotor Study of Children with ADHD

In 2007 Brašić questioned the methodology used by Pedersen and Surburg to test the effect of stimulant medication on lower extremity motor processing of children with attention deficit hyperactivity disorder (ADHD). The purpose of this response is to clarify the research design used in that 2005 study.

Reliability and sensitivity of jerk-cost measurement for evaluating irregularity of chewing jaw movements

Rate of change in movement acceleration (jerk) is a universally accepted quantity to evaluate irregularities of human limb and eye movements. This study was aimed to attest reliability of the jerk measurement of masticatory jaw movements and to identify its sensitivity to discriminate between movements performed with the presence of varied occlusal interference. Jaw movements during gum chewing were recorded with a 3D tracking device. Twelve adult subjects participated in the experiments. For five subjects, normalized jerk-costs (NJC) during jaw closing were compared between those measured on two separate occasions. For seven subjects, the NJCs during closing were compared with those measured with/without introduction of four different types of occlusal interference. The NJCs did not differ significantly between the two recording occasions. The interference at the canine tooth induced greater increase in the NJCs than that at the molar tooth. The comparison between repeated measures revealed reproducibility of the NJCs. In addition, the NJC was shown to be capable of discriminating between irregularities of the movements induced by occlusal interference at the canine and molar tooth sites. These findings suggest that the NJC is a valid indicator of masticatory jaw movement irregularity induced by disturbances of full intercuspation between upper and lower teeth.

ADHD and DCD: A relationship in need of research

Although the connection between attention deficit hyperactivity disorder (ADHD) and developmental coordination disorder (DCD) has been recognized for several decades, little research has examined the relationship between these two disorders. This paper draws attention to the contribution the cognitive-energetic model (CEM) can make in determining the specific nature of these two disorders. An information processing approach such as the CEM is a useful model to identify specific and overlapping mechanisms that are disrupted in these two disorders. This paper describes the CEM and reviews the research so-far in relation to the model. The CEM has several advantages over other models: First, it predicts which task variables will be independent or may interact, thus enabling the investigator to determine the success/failure of the task manipulation(s) and identify spurious findings. Second, the CEM links energetic factors to task variables and predicts both additive and interactive effects. Third, the CEM enables executive processes such as selective attention, working memory and inhibition to be related to both energetic and lower level processes. Fourth, by employing the CEM in clinical research, taxonomy of deficits can be derived enabling further insight into the nature of the disorders and their specific neuropsychological dysfunction. Suggestions are made for future research into the neuropsychological deficits associated with ADHD and DCD.

Moment-to-moment dynamics of ADHD behaviour

Background

The behaviour of children with Attention-Deficit / Hyperactivity Disorder is often described as highly variable, in addition to being hyperactive, impulsive and inattentive. One reason might be that they do not acquire complete and functional sequences of behaviour. The dynamic developmental theory of ADHD proposes that reinforcement and extinction processes are inefficient because of hypofunctioning dopamine systems, resulting in a narrower time window for associating antecedent stimuli and behaviour with its consequences. One effect of this may be that the learning of behavioural sequences is delayed, and that only short behavioural sequences are acquired in ADHD. The present study investigated acquisition of response sequences in the behaviour of children with ADHD.

Methods

Fifteen boys with ADHD and thirteen boys without, all aged between 6–9 yr, completed a computerized task presented as a game with two squares on the screen. One square was associated with reinforcement. The task required responses by the computer mouse under reinforcement contingencies of variable interval schedules. Reinforcers were cartoon pictures and small trinkets. Measures related to response location (spatial dimension) and to response timing (temporal dimension) were analyzed by autocorrelations of consecutive responses across five lags. Acquired response sequences were defined as predictable responding shown by high explained variance.

Results

Children with ADHD acquired shorter response sequences than comparison children on the measures related to response location. None of the groups showed any predictability in response timing. Response sequencing on the measure related to the discriminative stimulus was highly related to parent scores on a rating scale for ADHD symptoms.

Conclusion

The findings suggest that children with ADHD have problems with learning long sequences of behaviour, particularly related to response location. Problems with learning long behavioural sequences may ultimately lead to deficient development of verbally governed behaviour and self control. The study represents a new approach to analyzing the moment-to-moment dynamics of behaviour, and provides support for the theory that reinforcement processes are altered in ADHD.

Modeling attention-deficit/hyperactivity disorder: a critical appraisal of the cognitive-energetic model

A number of theoretical models of attention-deficit/hyperactivity disorder (ADHD) have emerged in recent years that may be used as systematic guides for clinical research. The cognitive-energetic model (CEM) proposes that the overall efficiency of information processing is determined by the interplay of three levels: computational mechanisms of attention, state factors, and management/executive function (EF). The CEM encompasses both top-down and bottom-up processes and draws attention to the fact that ADHD causes defects at all three levels. These include cognitive mechanisms, such as response output; energetic mechanisms, such as activation and effort; and management/EF deficits. Increasing evidence suggests that inhibition deficits associated with ADHD may, at least in part, be explained in terms of an energetic dysfunction. The activation and effort energetic pools appear most relevant to ADHD, being directly related to response organization; however, further testing of CEM is critically dependent on the development of direct measures of these energetic pools. The CEM is a comprehensive model of ADHD but is not without limitations. In particular, further research is required to define more specifically the relationship between process dysfunction and state dysregulation in ADHD.

Studies in motor behavior: 75 years of research in motor development, learning, and control

Research focused on human motor development, learning, and control has been a prominent feature in the Research Quarterly for Exercise and Sport (RQES) since it was first published in 1930. The purpose of this article is to provide an overview of the papers in the RQES that demonstrate the journal's contributions to the study of motor development, learning, and control. The landmark study by Henry and Rogers (1960), the C. H. McCloy lectures, and theoretical and review papers in motor behavior are highlighted. The RQES has served as a significant outlet for research in development, learning, and control throughout its 75-year history. The convergence of the theories, research methods and analytical tools lead to the proposition that these three areas have evolved into afield best described as motor behavior.

Bildgebende Darstellung neurokognitiver Dysfunktionen bei der Aufmerksamkeitsdefizit-/Hyperaktivit�tsst�rung

Attention Deficit Hyperactivity Disorder (ADHD) is a neurobiological disorder of early childhood onset. Defining symptoms are chronic impairments of attention, impulse control and motor hyperactivity that frequently persist until adulthood. Miscellaneous causes of the disorder have been discussed. Accumulating evidence from imaging- and molecular genetic studies strengthened the theory of ADHS being a predominantly inherited disorder of neurobiological origin. In the last 15 years, non-invasive brain imaging methods were successfully implemented in pediatric research. Functional magnetic resonance imaging studies gave major insight into the neurobiological correlates of executive malfunction, inhibitory deficits and psychomotoric soft signs. These findings are in good accordance with brain morphometric data indicating a significant volumetric decrease of major components of striato-thalamo-cortical feedback loops, primarily influencing prefrontal executive functioning (e.g. basal ganglia). Empirical evidence points to a broad array of associated behavioral disturbances like deficient visuomotor abilities and oculomotor dysfunctions. This paper reviews the current empirical evidence derived from prior imaging studies. Special emphasis is given to the relevance of oculomotor dysfunctions in clinical and research settings, as well as their assessment in the MR environment.

Neuromotor noise limits motor performance, but not motor adaptation, in children

Children do not typically appear to move with the same skill and dexterity as adults, although they can still improve their motor performance in specific tasks with practice. One possible explanation is that their motor performance is limited by an inherently higher level of movement variability, but that their motor adaptive ability is robust to this variability. To test this hypothesis, we examined motor adaptation of 43 children (ages 6-17) and 12 adults as they reached while holding the tip of a lightweight robot. The robot applied either a predictable, velocity-dependent field (the "mean field") or a similar field that incorporated stochastic variation (the "noise field"), thereby further enhancing the variability of the subjects' movements. We found that children exhibited greater initial trial-to-trial variability in their unperturbed movements but were still able to adapt comparably to adults in both the mean and noise fields. Furthermore, the youngest children (ages 6-8) were able to reduce their variability with practice to levels comparable to the remaining children groups although not as low as adults. These results indicate that children as young as age 6 possess adult-like neural systems for motor adaptation and internal model formation that allow them to adapt to novel dynamic environments as well as adults on average despite increased neuromotor or environmental noise. Performance after adaptation is still more variable than adults, however, indicating that movement inconsistency, not motor adaptation inability, ultimately limits motor performance by children and may thus account for their appearance of incoordination and more frequent motor accidents (e.g., spilling, tripping). The results of this study also suggest that movement variability in young children may arise from two sources--a relatively constant, intrinsic source related to fundamental physiological constraints of the developing motor system and a more rapidly modifiable source that is modulated depending on the current motor context.