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Recent neuroimaging studies have reported atypical neural activation in children with Developmental Coordination Disorder (DCD) during tasks assessing manual dexterity. However, small sample sizes and subtle differences in task parameters have led to inconsistent findings, rendering interpretation difficult. The aim of the present meta-analysis was to quantitatively summarize this body of evidence using activation likelihood estimation (ALE) analysis to identify reliable regions of differential neural activation in children with DCD, compared to age-matched controls. Seven studies that adopted f MRI to compare children with and without DCD during manual performance were identified following a literature search. All were included in the ALE analysis. Compared to controls, children with DCD showed reduced activation during a manual dexterity task in the middle frontal gyrus, superior frontal gyrus, cerebellum, supramarginal gyrus, and inferior parietal lobule. Children with DCD showed greater activation in parts of the thalamus. Findings provide much needed clarification into the possible neural contributors to atypical manual dexterity in DCD and highlight the need for neuroimaging studies to include manual performance outcomes. [ABSTRACT FROM AUTHOR]

Graph theory (GT) is a powerful framework for quantifying topological features of neuroimaging-derived functional and structural networks. However, false positive (FP) connections arise frequently and influence the inferred topology of networks. Thresholding is often used to overcome this problem, but an appropriate threshold often relies on a priori assumptions, which will alter inferred network topologies. Four common network metrics (global efficiency, mean clustering coefficient, mean betweenness and smallworldness) were tested using a model tractography dataset. It was found that all four network metrics were significantly affected even by just one FP. Results also show that thresholding effectively dampens the impact of FPs, but at the expense of adding significant bias to network metrics. In a larger number ( n = 248) of tractography datasets, statistics were computed across random group permutations for a range of thresholds, revealing that statistics for network metrics varied significantly more than for non-network metrics (i.e., number of streamlines and number of edges). Varying degrees of network atrophy were introduced artificially to half the datasets, to test sensitivity to genuine group differences. For some network metrics, this atrophy was detected as significant ( p < 0.05, determined using permutation testing) only across a limited range of thresholds. We propose a multi-threshold permutation correction (MTPC) method, based on the cluster-enhanced permutation correction approach, to identify sustained significant effects across clusters of thresholds. This approach minimises requirements to determine a single threshold a priori . We demonstrate improved sensitivity of MTPC-corrected metrics to genuine group effects compared to an existing approach and demonstrate the use of MTPC on a previously published network analysis of tractography data derived from a clinical population. In conclusion, we show that there are large biases and instability induced by thresholding, making statistical comparisons of network metrics difficult. However, by testing for effects across multiple thresholds using MTPC, true group differences can be robustly identified. [ABSTRACT FROM AUTHOR]

Recent research on traumatic brain injury (TBI) has shown that impairments in cognitive and executive control functions are accompanied by a disrupted neural connectivity characterized by white matter damage. We constructed binary and weighted brain structural networks in 21 patients with chronic TBI and 17 healthy young adults utilizing diffusion tensor tractography and calculated topological properties of the networks using a graph theoretical method. Executive function was assessed with the local global task and the trail making task, requiring inhibition, updating, and switching. The results revealed that TBI patients were less successful than controls on the executive tasks, as shown by the higher reaction times, higher switch costs, and lower accuracy rates. Moreover, both TBI patients and controls exhibited a small world topology in their white matter networks. More importantly, the TBI patients demonstrated increased shortest path length and decreased global efficiency of the structural network. These findings suggest that TBI patients have a weaker globally integrated structural brain network, resulting in a limited capacity to integrate information across brain regions. Furthermore, we showed that the white matter networks of both groups contained highly connected hub regions that were predominately located in the parietal cortex, frontal cortex, and basal ganglia. Finally, we showed significant correlations between switching performance and network property metrics within the TBI group. Specifically, lower scores on the switching tasks corresponded to a lower global efficiency. We conclude that analyzing the structural brain network connectivity provides new insights into understanding cognitive control changes following brain injury. [ABSTRACT FROM AUTHOR]

Abstract: Traumatic brain injury (TBI) patients have a high incidence of eye–hand coordination deficits. Diffuse axonal injury is common in TBI and is presumed to contribute to persistent motor problems. Using Diffusion Tensor Imaging (DTI), this study sought to identify changes in (sensori)motor white matter (WM) pathways/regions in a TBI group during the chronic recovery stage. A secondary objective was to examine the relationship between WM integrity and upper-limb visuomotor tracking performance. A young TBI (n =17) and control (n =14) group performed a dynamic tracking task, characterized by increasing information processing speed and predictive movement control. DTI scans were administered along with standard anatomical scans. The TBI group was found to perform inferior to the control group on the tracking task. Decreased fractional anisotropy was found in the TBI group in dedicated pathways involved in transmission of afferent and efferent information, i.e., corticospinal tract, posterior thalamic radiation, and optic radiation, due to increased diffusivity parallel and perpendicular to axonal fibre direction. This decrease in WM integrity was associated with inferior visuomotor tracking performance. Moreover, discriminant function analysis demonstrated that the model, based on the combined application of DTI and behavioral measures, was the most effective in distinguishing between TBI patients and controls. This study shows that specific eye–hand coordination deficits in a young TBI group are related to microstructural abnormalities in task-specific cerebral WM structures. Measures of white matter integrity are potentially important biomarkers for TBI that may support prognosis of motor deficits. [Copyright &y& Elsevier]

Abstract: Motor disorders are a frequent consequence of acquired brain injury (ABI) in children and much effort is currently invested in alleviating these deficits. The aim of the present study was to test motor imagery (MI) capabilities in children with ABI (n =25) and an age- and gender-matched control group (n =25). A computerized Virtual Radial Fitts Task (VRFT) was used to investigate the speed-accuracy trade-offs (or Fitts’ law) that occur as target size is varied for both executed and imagined performance. In the control group, the speed for accuracy trade-off for both executed and imagined performance conformed to Fitts’ law. In the ABI group, only executed movements conformed to Fitts’ law. These findings suggest that children with ABI show an inferior ability to imagine the time needed to complete goal-directed movements with differential difficulty levels. [Copyright &y& Elsevier]

Abstract: Brain alterations are hypothesized to be present in patients with chronic whiplash‐associated disorders (CWAD). The aim of this case–control study was to examine alterations in cortical thickness and white matter (WM) structure, and the presence of brain microhemorrhages in a patient group encountering chronic neck pain of traumatic origin (i.e., CWAD) when compared with a patient group characterized by nontraumatic chronic neck pain [i.e., chronic idiopathic neck pain (CINP)], and healthy controls. Furthermore, we aimed to investigate associations between brain structure on one hand and cognitive performance and central sensitization (CS) on the other hand. T1‐weighted, diffusion‐weighted and T2*‐weighted magnetic resonance images of the brain were acquired in 105 women (31 controls, 37 CINP, 37 CWAD) to investigate regional cortical thickness, WM structure, and microhemorrhages, respectively. Next, cognitive performance, and CS encompassing distant hyperalgesia and conditioned pain modulation (CPM) efficacy were examined. Cortical thinning in the left precuneus was revealed in CWAD compared with CINP patients. Also, decreased fractional anisotropy, together with increased values of mean diffusivity and radial diffusivity could be observed in the left cingulum hippocampus and tapetum in CWAD compared with CINP, and in the left tapetum in CWAD patients compared with controls. Moreover, the extent of WM structural deficits in the left tapetum coincided with decreased CPM efficacy in the CWAD group. This yields evidence for associations between decreased endogenous pain inhibition, and the degree of regional WM deficits in CWAD. Our results emphasize the role of structural brain alterations in women with CWAD compared with CINP. [ABSTRACT FROM AUTHOR]

Loss of brain-specific dystrophin has been implicated in the heightened predisposition of patients and vertebrate models of Duchenne muscular dystrophy (DMD) to stressful stimuli. Using 18F-fluorodeoxyglucose uptake by positron emission tomography (18FDG PET) to assess metabolic tissue activity, we measured decreased 18FDG uptake in most brain regions and marginally increased uptake in skeletal muscle of wildtype mice following stress. By contrast, 18FDG uptake did not change in brain and decreased in striated muscle in the mdx mouse model of DMD in response to stress, suggesting dysfunctional glucose-insulin signalling. Glucose intolerance in mdx mice was exacerbated by stress and driven not by an insensitivity to insulin, but by an inability to synthesize insulin. Exogenous administration of naked insulin mitigated immediate stress-induced physical inactivity (indirect measure of stress sensitivity), lowered 18FDG uptake in brain and elevated 18FDG uptake in striated muscle of mdx mice in response to stress. These data indicate that during stress, dystrophin-deficiency impairs the ability of brain and striated muscle to respond metabolically appropriately. It also suggests that the hypersensitive stress phenotype of mdx mice is associated with dysfunctional glucose-insulin signalling that can be mitigated with exogenous insulin. [ABSTRACT FROM AUTHOR]

Age-related changes in the microstructural organization of the corpus callosum (CC) may explain declines in bimanual motor performance associated with normal aging. We used diffusion tensor imaging in young ( n = 33) and older ( n = 33) adults to investigate the microstructural organization of seven specific CC subregions (prefrontal, premotor, primary motor, primary sensory, parietal, temporal and occipital). A set of bimanual tasks was used to assess various aspects of bimanual motor functioning: the Purdue Pegboard test, simultaneous and alternating finger tapping, a choice reaction time test and a complex visuomotor tracking task. The older adults showed age-related deficits on all measures of bimanual motor performance. Correlation analyses within the older group showed that white matter fractional anisotropy of the CC occipital region was associated with bimanual fine manipulation skills (Purdue Pegboard test), whereas better performance on the other bimanual tasks was related to higher fractional anisotropy in the more anterior premotor, primary motor and primary sensory CC subregions. Such associations were less prominent in the younger group. Our findings suggest that structural alterations of subregional callosal fibers may account for bimanual motor declines in normal aging. [ABSTRACT FROM AUTHOR]

Abstract: We recently found that spontaneous eye movements occur during motor imagery of hand movements, which are similar to those made during physical execution. In physical execution, eye movements have been shown to play an important role during training. In motor imagery practice, however, their effect remains unclear. Therefore, in the present study, we examined the role of eye movements during motor imagery practice with specific interest in the impact of task complexity and effector specificity. Thirty-six young healthy participants were tested before and after 4 days of visual motor imagery training on a Virtual Radial Fitts'' task with different indices of difficulty. Training was performed with the nondominant hand only. Subjects were divided into a group that trained while spontaneous eye movements were allowed, one that kept the eyes fixed during training, and a control group. Electro-oculography and electromyography signals were monitored to guarantee task compliance during imagery. The results indicated that eye movements during imagery did not affect the temporal parameters of the trained movement. They did, however, help to achieve maximal gains in movement accuracy and efficiency. These positive effects on the spatial parameters were most pronounced during conditions with high accuracy demands and were present for both the trained and the untrained hand. These findings contribute to guidelines for optimizing training protocols based on motor imagery. [Copyright &y& Elsevier]

Recent research suggests that children with Developmental Coordination Disorder (DCD) often show deficits in executive functioning (EF) and, more specifically, the ability to use inhibitory control in 'hot', emotionally rewarding contexts. This study optimized the assessment of sensitivity of children with DCD to emotionally significant stimuli by using easily discriminable emotional expressions in a go/no-go task. Thirty-six children (12 with DCD), aged 7-12years, completed an emotional go/no-go task in which neutral facial expressions were paired with either happy or sad ones. Each expression was used as both, a go and no-go target in different runs of the task. There were no group differences in omission errors; however, the DCD group made significantly more commission errors to happy no-go faces. The particular pattern of performance in DCD confirms earlier reports of (hot) EF deficits. Specifically, a problem of inhibitory control appears to underlie the atypical pattern of performance seen in DCD on both cold and hot EF tasks. Disrupted coupling between cognitive control and emotion processing networks, such as fronto-parietal and fronto-striatal networks, may contribute to reduced inhibitory control in DCD. The implications for a broader theoretical account of DCD are discussed, as are implications for intervention. [ABSTRACT FROM AUTHOR]

Diffusion tensor imaging (DTI) characterizes white matter (WM) microstructure. In many brain regions, however, the assumption that the diffusion probability distribution is Gaussian may be invalid, even at low b values. Recently, diffusion kurtosis imaging (DKI) was suggested to more accurately estimate this distribution. We explored the added value of DKI in studying the relation between WM microstructure and upper limb coordination in healthy controls ( N = 24). Performance on a complex bimanual tracking task was studied with respect to the conventional DTI measures (DKI or DTI derived) and kurtosis metrics of WM tracts/regions carrying efferent (motor) output from the brain, corpus callosum (CC) substructures and whole brain WM. For both estimation models, motor performance was associated with fractional anisotropy (FA) of the CC-genu, CC-body, the anterior limb of the internal capsule, and whole brain WM ( r range 0.42-0.63). Although DKI revealed higher mean, radial and axial diffusivity and lower FA than DTI ( p < 0.001), the correlation coefficients were comparable. Finally, better motor performance was associated with increased mean and radial kurtosis and kurtosis anisotropy ( r range 0.43-0.55). In conclusion, DKI provided additional information, but did not show increased sensitivity to detect relations between WM microstructure and bimanual performance in healthy controls. [ABSTRACT FROM AUTHOR]

Abstract: Complex bimanual motor learning causes specific changes in activation across brain regions. However, there is little information on how motor learning changes the functional connectivity between these regions, and whether this is influenced by different sensory feedback modalities. We applied graph-theoretical network analysis (GTNA) to examine functional networks based on motor-task-related fMRI activations. Two groups learned a complex 90° out-of-phase bimanual coordination pattern, receiving either visual or auditory feedback. 3T fMRI scanning occurred before (day 0) and after (day 5) training. In both groups, improved motor performance coincided with increased functional network connectivity (increased clustering coefficients, higher number of network connections and increased connection strength, and shorter communication distances). Day×feedback interactions were absent but, when examining network metrics across all examined brain regions, the visual group had a marginally better connectivity, higher connection strength, and more direct communication pathways. Removal of feedback had no acute effect on the functional connectivity of the trained networks. Hub analyses showed an importance of specific brain regions not apparent in the standard fMRI analyses. These findings indicate that GTNA can make unique contributions to the examination of functional brain connectivity in motor learning. [Copyright &y& Elsevier]