RESUMEN
In adults, individual differences in procedural learning (PL) are associated with white matter organization within the basal ganglia-cerebellar circuit. However, no research has examined whether this circuitry is related to individual differences in PL during childhood. Here, 28 children (Mage = 10.00 ± 2.31, 10 female) completed the serial reaction time (SRT) task to measure PL, and underwent structural magnetic resonance imaging (MRI). Fixel-Based Analysis was performed to extract specific measures of white matter fiber density (FD) and fiber cross-section (FC) from the superior cerebellar peduncles (SCP) and the striatal premotor tracts (STPMT), which underlie the fronto-basal ganglia-cerebellar system. These fixel metrics were correlated with the 'rebound effect' from the SRT task - a measure of PL proficiency which compares reaction times associated with generating a sequence, to random trials. While no significant associations were observed at the fixel level, a significant positive association was observed between average FD in the right SCP and the rebound effect, with a similar trend observed in the left SCP. No significant effects were detected in the STPMT. Our results indicate that, like in adults, microstructure of the basal ganglia-cerebellar circuit may explain individual differences in childhood PL.
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Ganglios Basales , Cerebelo , Aprendizaje , Imagen por Resonancia Magnética , Sustancia Blanca , Humanos , Femenino , Masculino , Cerebelo/fisiología , Cerebelo/diagnóstico por imagen , Ganglios Basales/fisiología , Niño , Imagen por Resonancia Magnética/métodos , Aprendizaje/fisiología , Sustancia Blanca/diagnóstico por imagen , Sustancia Blanca/fisiología , Tiempo de Reacción/fisiología , Vías Nerviosas/fisiología , IndividualidadRESUMEN
Despite the important role of motor imagery (MI) in motor development, our understanding of the contribution of white matter fibre properties to MI performance in childhood remains limited. To provide novel insight into the white matter correlates of MI performance, this study examined the association between white matter fibre properties and motor imagery performance in a sample of typically developing children. High angular diffusion weighted imaging data were collected from 22 typically developing children aged 6-14 years (12 female, MAge= 10.56). Implicit motor imagery performance was assessed using a mental hand rotation paradigm. The cerebellar peduncles and the superior longitudinal fasciculus were reconstructed using TractSeg, a semi-automated method. For each tract, white matter microstructure (fibre density, FD) and morphology (fibre bundle cross-section, FC) were estimated using Fixel-Based Analysis. Permutation-based inference testing and partial correlation analyses demonstrated that higher FC in the middle cerebellar peduncles was associated with better MI performance. Tract-based region of interest analyses showed that higher FC in the middle and superior cerebellar peduncles were associated with better MI performance. Results suggest that white matter connectivity along the cerebellar peduncles may facilitate MI performance in childhood. These findings advance our understanding of the neurobiological systems that underlie MI performance in childhood and provide early evidence for the relevance of white matter sensorimotor pathways to internal action representations.
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Imaginación , Sustancia Blanca , Humanos , Femenino , Niño , Masculino , Sustancia Blanca/diagnóstico por imagen , Sustancia Blanca/fisiología , Adolescente , Imaginación/fisiología , Imagen de Difusión por Resonancia Magnética , Vías Nerviosas/fisiología , Desempeño Psicomotor/fisiología , Imagen de Difusión Tensora , Mapeo EncefálicoRESUMEN
While procedural learning (PL) has been implicated in delayed motor skill observed in developmental coordination disorder (DCD), few studies have considered the impact of co-occurring attentional problems. Furthermore, the neurostructural basis of PL in children remains unclear. We investigated PL in children with DCD while controlling for inattention symptoms, and examined the role of fronto-basal ganglia-cerebellar morphology in PL. Fifty-nine children (6-14 years; nDCD = 19, ncontrol = 40) completed the serial reaction time (SRT) task to measure PL. The Attention-Deficit Hyperactivity Disorder Rating Scale-IV was administered to measure inattention symptoms. Structural T1 images were acquired for a subset of participants (nDCD = 10, ncontrol = 28), and processed using FreeSurfer. Volume was extracted for the cerebellum, basal ganglia, and frontal regions. After controlling for inattention symptoms, the reaction time profile of controls was consistent with learning on the SRT task. This was not the case for those with DCD. SRT task performance was positively correlated with cerebellar cortical volume, and children with DCD trended towards lower cerebellar volume compared to controls. Children with DCD may not engage in PL during the SRT task in the same manner as controls, with this differential performance being associated with atypical cerebellar morphology.
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Cerebelo , Aprendizaje , Imagen por Resonancia Magnética , Trastornos de la Destreza Motora , Tiempo de Reacción , Humanos , Niño , Masculino , Femenino , Adolescente , Trastornos de la Destreza Motora/fisiopatología , Trastornos de la Destreza Motora/diagnóstico por imagen , Tiempo de Reacción/fisiología , Cerebelo/diagnóstico por imagen , Cerebelo/fisiopatología , Aprendizaje/fisiología , Imagen por Resonancia Magnética/métodos , Trastorno por Déficit de Atención con Hiperactividad/fisiopatología , Trastorno por Déficit de Atención con Hiperactividad/diagnóstico por imagen , Neuroimagen/métodos , Atención/fisiología , Ganglios Basales/fisiopatología , Ganglios Basales/diagnóstico por imagen , Desempeño Psicomotor/fisiología , Destreza Motora/fisiologíaRESUMEN
Myelination of human brain white matter (WM) continues into adulthood following birth, facilitating connection within and between brain networks. In vivo MRI studies using diffusion weighted imaging (DWI) suggest microstructural properties of brain WM increase over childhood and adolescence. Although DWI metrics, such as fractional anisotropy (FA), could reflect axonal myelination, they are not specific to myelin and could also represent other elements of WM microstructure, for example, fibre architecture, axon diameter and cell swelling. Little work exists specifically examining myelin development. The T1w/T2w ratio approach offers an alternative non-invasive method of estimating brain myelin. The approach uses MRI scans that are routinely part of clinical imaging and only require short acquisition times. Using T1w/T2w ratio maps from three waves of the Neuroimaging of the Children's Attention Project (NICAP) [N = 95 (208 scans); 44% female; ages 9.5-14.20 years] we aimed to investigate the developmental trajectories of brain white matter myelin in children as they enter adolescence. We also aimed to investigate whether longitudinal changes in myelination of brain WM differs between biological sex. Longitudinal regression modelling suggested non-linear increases in WM myelin brain wide. A positive parabolic, or U-shaped developmental trajectory was seen across 69 of 71 WM tracts modelled. At a corrected level, no significant effect for sex was found. These findings build on previous brain development research by suggesting that increases in brain WM microstructure from childhood to adolescence could be attributed to increases in myelin.
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Sustancia Blanca , Adolescente , Humanos , Niño , Femenino , Masculino , Sustancia Blanca/diagnóstico por imagen , Vaina de Mielina , Encéfalo/diagnóstico por imagen , Imagen por Resonancia Magnética/métodos , Imagen de Difusión por Resonancia MagnéticaRESUMEN
It is well documented that attention-deficit hyperactivity disorder (ADHD) often presents with co-occurring motor difficulties. However, little is known about the biological mechanisms that explain compromised motor skills in approximately half of those with ADHD. To provide insight into the neurobiological basis of poor motor outcomes in ADHD, this study profiled the development of white matter organization within the cortico-spinal tract (CST) in adolescents with ADHD with and without co-occurring motor problems, as well as non-ADHD control children with and without motor problems. Participants were 60 children aged 9-14 years, 27 with a history of ADHD and 33 controls. All underwent high-angular resolution diffusion MRI data at up to three time points (115 in scans total). We screened for motor impairment in all participants at the third time point (≈14 years) using the Developmental Coordination Disorder Questionnaire (DCD-Q). Following pre-processing of diffusion MRI scans, fixel-based analysis was performed, and the bilateral CST was delineated using TractSeg. Mean fiber density (FD) and fiber cross-section (FC) were extracted for each tract at each time-point. To investigate longitudinal trajectories of fiber development, linear mixed models were performed separately for the left and right CST, controlling for nuisance variables. To examine possible variations in fiber development between groups, we tested whether the inclusion of group and the interaction between age and group improved model fit. At ≈10 years, those with ADHD presented with lower FD within the bilateral CST relative to controls, irrespective of their prospective motor status. While these microstructural abnormalities persisted into adolescence for individuals with ADHD and co-occurring motor problems, they resolved for those with ADHD alone. Divergent maturational pathways of motor networks (i.e., the CST) may, at least partly, explain motor problems individuals with ADHD.
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Trastorno por Déficit de Atención con Hiperactividad , Sustancia Blanca , Niño , Humanos , Adolescente , Trastorno por Déficit de Atención con Hiperactividad/complicaciones , Trastorno por Déficit de Atención con Hiperactividad/diagnóstico por imagen , Tractos Piramidales/diagnóstico por imagen , Estudios Prospectivos , Encéfalo , Sustancia Blanca/diagnóstico por imagenRESUMEN
Fixel-based analysis was used to probe age-related changes in white matter micro- and macrostructure of the corpus callosum between participants with (N = 54) and without (N = 50) autism spectrum disorder (ASD). Data were obtained from the Autism Brain Imaging Data Exchange-II (ABIDE-II). Compared to age-matched controls, young adolescents with ASD (11.19 ± 7.54 years) showed reduced macroscopic fiber cross-section (logFC) and combined fiber-density and cross-section (FDC). Reduced fiber-density (FD) and FDC was noted in a marginally older (13.87 ± 3.15 years) ASD cohort. Among the oldest ASD cohort (17.07 ± 3.56 years), a non-significant trend indicative of reduced FD was noted. White matter aberration appears greatest and most widespread among younger ASD cohorts. This supports the suggestion that some early neuropathophysiological indicators in ASD may dissipate with age.
RESUMEN
Functional neuroimaging has consistently implicated the fronto-basal ganglia-cerebellar circuit in procedural learning-defined as the incidental acquisition of sequence information through repetition. Limited work has probed the role of white matter fiber pathways that connect the regions in this network, such as the superior cerebellar peduncles (SCP) and the striatal premotor tracts (STPMT), in explaining individual differences in procedural learning. High angular diffusion weighted imaging was acquired from 20 healthy adults aged 18-45 years. Fixel-based analysis was performed to extract specific measures of white matter microstructure (fiber density; FD) and macrostructure (fiber cross-section; FC), from the SCP and STPMT. These fixel metrics were correlated with performance on the serial reaction time (SRT) task, and sensitivity to the sequence was indexed by the difference in reaction time between the final block of sequence trials and the randomized block (namely, the 'rebound effect'). Analyses revealed a significant positive relationship between FD and the rebound effect in segments of both the left and right SCP (pFWE < .05). That is, increased FD in these tracts was associated with greater sensitivity to the sequence on the SRT task. No significant associations were detected between fixel metrics in the STPMT and the rebound effect. Our results support the likely role of white matter organization in the basal ganglia-cerebellar circuit in explaining individual differences in procedural learning.
Asunto(s)
Sustancia Blanca , Humanos , Adulto , Sustancia Blanca/diagnóstico por imagen , Individualidad , Imagen de Difusión por Resonancia Magnética , Cerebelo/diagnóstico por imagen , Ganglios Basales/diagnóstico por imagenRESUMEN
BACKGROUND: Few longitudinal studies have investigated whether white matter development reflects differential outcomes for children with and without attention-deficit/hyperactivity disorder (ADHD). To examine whether deviations from typical trajectories of white matter development were associated with the persistence or remission of ADHD symptoms, this study examined microstructural and morphological properties of 71 white matter tracts from 390 high angular diffusion scans acquired prospectively for 62 children with persistent ADHD, 37 children remitted from ADHD, and 85 children without ADHD. METHODS: Participants (mean age at wave 1 = 10.39 years, scan interval = 18 months) underwent up to 3 magnetic resonance imaging assessments. White matter tracts were reconstructed using TractSeg, a semiautomated method. For each tract, we derived measures of fiber density (microstructure) and fiber bundle cross-section (morphology) using fixel-based analysis. Linear mixed models were used to compare trajectories of fiber development between the persistent ADHD, remitted ADHD, and non-ADHD groups. RESULTS: Compared with the non-ADHD group, the remitted and persistent ADHD groups showed accelerated fiber development in thalamic pathways, striatal pathways, and the superior longitudinal fasciculus. In the remitted ADHD group, accelerated fiber development in corticospinal, frontopontine, striatal-premotor, and thalamo-premotor pathways was associated with greater reductions in ADHD symptom severity. The persistent ADHD group showed ongoing white matter alterations along sensorimotor pathways. CONCLUSIONS: These results suggest that variations in white matter development are associated with different clinical trajectories in ADHD. The findings advance our understanding of the neurobiological mechanisms underpinning ADHD symptom progression and provide novel evidence in support of developmental models of ADHD.
Asunto(s)
Trastorno por Déficit de Atención con Hiperactividad , Sustancia Blanca , Niño , Humanos , Trastorno por Déficit de Atención con Hiperactividad/diagnóstico , Imagen por Resonancia Magnética , Atención , Red NerviosaRESUMEN
This study investigated sex and age differences in autistic behaviours in children with neurofibromatosis type 1 (NF1) who scored within the clinical range on the Social Responsiveness Scale - Second Edition (T score ≥ 60). Thirty-four males and 28 females (3-16 years) were assessed with the Autism Diagnostic Observation Schedule - Second Edition and Autism Diagnostic Interview - Revised. Across both measures, males exhibited greater social communication deficits relative to females. Age-related abatement of social communication difficulties was observed for males but not females. Conversely, no sex differences were found for restricted/repetitive behaviours, which were stable over time for both males and females. The findings are discussed within the context of broader neurodevelopmental considerations that are common in NF1.
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Trastorno del Espectro Autista , Trastorno Autístico , Neurofibromatosis 1 , Masculino , Humanos , Niño , Trastorno Autístico/diagnóstico , Neurofibromatosis 1/complicaciones , Neurofibromatosis 1/diagnóstico , Comunicación , LenguajeRESUMEN
Response inhibition refers to the cancelling of planned (or restraining of ongoing) actions and is required in much of our everyday life. Response inhibition appears to improve dramatically in early development and plateau in adolescence. The fronto-basal-ganglia network has long been shown to predict individual differences in the ability to enact response inhibition. In the current study, we examined whether developmental trajectories of fiber-specific white matter properties of the fronto-basal-ganglia network was predictive of parallel developmental trajectories of response inhibition. 138 children aged 9-14 completed the stop-signal task (SST). A subsample of 73 children underwent high-angular resolution diffusion MRI data for up to three time points. Performance on the SST was assessed using a parametric race modelling approach. White matter organization of the fronto-basal-ganglia circuit was estimated using fixel-based analysis. Contrary to predictions, we did not find any significant associations between maturational trajectories of fronto-basal-ganglia white matter and developmental improvements in SST performance. Findings suggest that the development of white matter organization of the fronto-basal-ganglia and development of stopping performance follow distinct maturational trajectories.
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Sustancia Blanca , Adolescente , Niño , Humanos , Inhibición Psicológica , Ganglios Basales/fisiología , Análisis y Desempeño de Tareas , GangliosRESUMEN
Sustained attention is a cognitive function with known links to academic success and mental health disorders such as attention/deficit-hyperactivity disorder (ADHD). Several functional networks are critical to sustained attention, however the association between white matter maturation in tracts linking functional nodes and sustained attention in typical and atypical development is unknown. 309 diffusion-weighted imaging scans were acquired from 161 children and adolescents (80 ADHD, 81 control) at up to three timepoints over ages 9-14. A fixel-based analysis approach was used to calculate mean fiber density and fiber-bundle cross section in tracts of interest. Sustained attention was measured using omission errors and response time variability on the out-of-scanner sustained attention to response task. Linear mixed effects models examined associations of age, group and white matter metrics with sustained attention. Greater fiber density in the bilateral superior longitudinal fasciculus (SLF) I and right SLF II was associated with fewer attention errors in the control group only. In ADHD and control groups, greater fiber density in the left ILF and right thalamo-premotor pathway, as well as greater fiber cross-section in the left SLF I and II and right SLF III, was associated with better sustained attention. Relationships were consistent across the age span. Results suggest that greater axon diameter or number in the dorsal and middle SLF may facilitate sustained attention in neurotypical children but does not assist those with ADHD potentially due to disorder-related alterations in this region. Greater capacity for information transfer across the SLF was associated with attention maintenance in 9-14-year-olds regardless of diagnostic status, suggesting white matter macrostructure may also be important for attention maintenance. White matter and sustained attention associations were consistent across the longitudinal study, according with the stability of structural organization over this time. Future studies can investigate modifiability of white matter properties through ADHD medications.
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Trastorno por Déficit de Atención con Hiperactividad , Sustancia Blanca , Niño , Adolescente , Humanos , Sustancia Blanca/diagnóstico por imagen , Estudios Longitudinales , Red Nerviosa , Imagen de Difusión por Resonancia MagnéticaRESUMEN
Transcranial magnetic stimulation (TMS) is used to probe inhibitory intracortical neurotransmission and has been used to infer the neurobiological dysfunction that may underly several neurological disorders. One technique, short-interval intracortical inhibition (SICI), indexes gamma-aminobutyric acid (GABA) mediated inhibitory activity and is a promising biomarker. However emerging evidence suggests SICI does not exclusively represent GABAergic activity because it may be influenced by inter-individual differences in the specific excitatory neural populations activated by TMS. Here we used the latency of TMS motor evoked potentials (MEPs) to index these inter-individual differences, and found that a significant proportion of the observed variability in SICI magnitude was accounted for by MEP latency, r = - 0.57, r2 = 0.33, p = .014. We conclude that SICI is influenced by inter-individual differences in the excitatory neural populations activated by TMS, reducing the precision of this GABAergic probe. Interpreting SICI measures in the context of MEP latency may facilitate a more precise assessment of GABAergic intracortical inhibition. The reduced cortical inhibition observed in some neuropathologies could be influenced by reduced activity in specific excitatory neural populations. Including MEP latency assessment in research investigating SICI in clinical groups could assist in differentiating the cortical circuits impacted by neurological disorders.
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Corteza Motora , Estimulación Magnética Transcraneal , Electromiografía , Potenciales Evocados Motores/fisiología , Individualidad , Corteza Motora/fisiología , Inhibición Neural/fisiología , Estimulación Magnética Transcraneal/métodosRESUMEN
While mentally simulated actions activate similar neural structures to overt movement, the role of the primary motor cortex (PMC) in motor imagery remains disputed. The aim of the study was to use continuous theta burst stimulation (cTBS) to modulate corticospinal activity to investigate the putative role of the PMC in implicit motor imagery in young adults with typical and atypical motor ability. A randomized, double blind, sham-controlled, crossover, offline cTBS protocol was applied to 35 young adults. During three separate sessions, adults with typical and low motor ability (developmental coordination disorder [DCD]), received active cTBS to the PMC and supplementary motor area (SMA), and sham stimulation to either the PMC or SMA. Following stimulation, participants completed measures of motor imagery (i.e., hand rotation task) and visual imagery (i.e., letter number rotation task). Although active cTBS significantly reduced corticospinal excitability in adults with typical motor ability, neither task performance was altered following active cTBS to the PMC or SMA, compared to performance after sham cTBS. These results did not differ across motor status (i.e., typical motor ability and DCD). These findings are not consistent with our hypothesis that the PMC (and SMA) is directly involved in motor imagery. Instead, previous motor cortical activation observed during motor imagery may be an epiphenomenon of other neurophysiological processes and/or activity within brain regions involved in motor imagery. This study highlights the need to consider multi-session theta burst stimulation application and its neural effects when probing the putative role of motor cortices in motor imagery.
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Corteza Motora , Método Doble Ciego , Potenciales Evocados Motores/fisiología , Mano/fisiología , Humanos , Imágenes en Psicoterapia , Corteza Motora/fisiología , Ritmo Teta/fisiología , Estimulación Magnética Transcraneal/métodos , Adulto JovenRESUMEN
BACKGROUND: Children with disabilities often engage in less than the recommended amount of daily physical activity (PA). Classroom-based PA breaks are a favourable method of promoting PA for children. However, evaluations of these programs in specialist schools are scarce, with even less research into their feasibility and acceptability. This may hinder effective implementation and program scalability. This pilot study investigated the feasibility and acceptability of implementing a classroom-based PA break program in Australian specialist school classrooms, using the Australian Joy of Moving (AJoM) program. METHODS: Forty primary/junior classes and their teachers across five specialist schools implemented the AJoM program for eight weeks as the intervention group within a pilot cluster randomised controlled trial. A mixed-methods design investigated classroom teachers' (N = 22; 6 males, 16 females) perspectives of the feasibility and acceptability of the program after implementation through semi-structured telephone interviews (n = 7 teachers), qualitative survey responses (n = 18 teachers) and quantitative survey items (n = 19 teachers). Qualitative data were analysed using predominantly deductive thematic analysis. Quantitative data were analysed using descriptive statistics. RESULTS: Classroom-based PA breaks may be feasible for getting children with disabilities more active at school. However, considerable variation exists in teachers' perception of the AJoM experience. While several teachers indicate that the program content could be pertinent for their class, common divergences in perceptions of feasibility and acceptability appear to relate to the age and developmental level or needs of the students in the class. CONCLUSIONS: This study provides preliminary evidence for the feasibility and acceptability of implementing classroom-based PA breaks in specialist schools. However, results demonstrate the importance of (1) allowing a high level of flexibility in the design and implementation of programs to meet the varying needs of class groups and (2) providing a large variety of resources to cater to the heterogeneity of the children. TRIAL REGISTRATION: This trial was prospectively registered with the Australian New Zealand Clinical Trials Registry ( ACTRN12619000193178 ) on 11 February 2019.
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Ejercicio Físico , Instituciones Académicas , Australia , Niño , Ejercicio Físico/fisiología , Estudios de Factibilidad , Femenino , Humanos , Masculino , Proyectos Piloto , Evaluación de Programas y Proyectos de Salud , Servicios de Salud EscolarRESUMEN
Previous Diffusion Tensor Imaging (DTI) studies in children suggest that developmental improvements in inhibitory control is largely mediated by the degree of white matter organisation within a right-lateralised network of fronto-basal-ganglia regions. Recent advances in diffusion imaging analysis now permit greater biological specificity, both in identifying specific fibre populations within a voxel, as well as in the underlying microstructural properties of that white matter. In the present work, employing a novel fixel-based analysis (FBA) framework, we aimed to comprehensively investigate microstructure within the fronto-basal-ganglia circuit in childhood, and its contribution to inhibition performance. Diffusion MRI data were obtained from 43 healthy children and adolescents aged 9-11 years (10.42 ± .41 years, 18 females). Response inhibition for each participant was assessed using the Stop-signal Task (SST) and quantified as a Stop-Signal Reaction Time (SSRT). All steps relevant to FBA were implemented in MRtrix3Tissue, a fork of the MRtrix3 software library. The fronto-basal-ganglia circuit were delineated using probabilistic tractography to identify the tracts connecting the subthalamic nucleus, pre-supplementary motor area and the inferior frontal gyrus. Connectivity-based fixel enhancement (CFE) was then used to assess the association between fibre density (FD) and fibre cross-section (FC) with inhibitory ability. Significant negative associations were identified for FD in both the right and left fronto-basal-ganglia circuit whereby greater FD was associated with better inhibition performance (e.g., reduced SSRTs). This effect was specifically localised to clusters of fixels within white matter proximal to the right subthalamic nucleus. We did not report any meaningful associations between SSRT and FC. Whilst findings are broadly consistent with prior DTI evidence, current results suggest that SSRT is predominantly facilitated by subcortical microstructure of the connections projecting from the subthalamic nucleus to the cortical regions of the network. Our findings extend current understanding of the role of white matter in childhood response inhibition.
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Imagen de Difusión Tensora , Sustancia Blanca , Adolescente , Ganglios Basales , Niño , Imagen de Difusión por Resonancia Magnética , Femenino , Ganglios , Humanos , Sustancia Blanca/diagnóstico por imagenRESUMEN
Diffusion MRI has provided the neuroimaging community with a powerful tool to acquire in-vivo data sensitive to microstructural features of white matter, up to 3 orders of magnitude smaller than typical voxel sizes. The key to extracting such valuable information lies in complex modelling techniques, which form the link between the rich diffusion MRI data and various metrics related to the microstructural organization. Over time, increasingly advanced techniques have been developed, up to the point where some diffusion MRI models can now provide access to properties specific to individual fibre populations in each voxel in the presence of multiple "crossing" fibre pathways. While highly valuable, such fibre-specific information poses unique challenges for typical image processing pipelines and statistical analysis. In this work, we review the "Fixel-Based Analysis" (FBA) framework, which implements bespoke solutions to this end. It has recently seen a stark increase in adoption for studies of both typical (healthy) populations as well as a wide range of clinical populations. We describe the main concepts related to Fixel-Based Analyses, as well as the methods and specific steps involved in a state-of-the-art FBA pipeline, with a focus on providing researchers with practical advice on how to interpret results. We also include an overview of the scope of all current FBA studies, categorized across a broad range of neuro-scientific domains, listing key design choices and summarizing their main results and conclusions. Finally, we critically discuss several aspects and challenges involved with the FBA framework, and outline some directions and future opportunities.
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Encéfalo/citología , Encéfalo/diagnóstico por imagen , Imagen de Difusión por Resonancia Magnética/métodos , Procesamiento de Imagen Asistido por Computador/métodos , Sustancia Blanca/diagnóstico por imagen , Encéfalo/fisiología , Imagen de Difusión por Resonancia Magnética/tendencias , Humanos , Procesamiento de Imagen Asistido por Computador/tendencias , Fibras Nerviosas/fisiología , Sustancia Blanca/fisiologíaRESUMEN
BACKGROUND: Motor imagery (MI) training may benefit children with congenital hemiplegia, but reports on MI ability are mixed. This study considered individual patterns of performance to better understand MI ability in children with hemiplegia. METHOD: Twenty children with hemiplegia (7-13 years; 10 with right hemiplegia), completed a MI task, IQ estimate and functional tests. Children with hemiplegia scoring above chance on the MI task were compared to a group of age-matched peers. The performance patterns of those scoring below chance were considered individually. RESULTS: Three children with right hemiplegia were excluded due to low IQ. Seven of 10 children with left hemiplegia and three of seven with right hemiplegia performed MI at an equivalent level to peers without hemiplegia. The seven children with hemiplegia who scored significantly below chance scored lower on functional tests, but differences here failed to reach an adjusted significance level. Four of the seven appeared engaged in MI, but performed very poorly. The remaining three had unique performance patterns explored in more detail. CONCLUSION: Motor imagery deficits are not universally observed in children with congenital hemiplegia and individual performance should be examined before completing group analyses. Recommendations for exclusions and reporting in future studies are made.
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Parálisis Cerebral , Hemiplejía , Niño , Humanos , ImaginaciónRESUMEN
While there have been consistent behavioural reports of atypical hand rotation task (HRT) performance in adults with developmental coordination disorder (DCD), this study aimed to clarify whether this deficit could be attributed to specific difficulties in motor imagery (MI), as opposed to broad deficits in general mental rotation. Participants were 57 young adults aged 18-30 years with (n = 22) and without DCD (n = 35). Participants were compared on the HRT, a measure of MI, and the letter number rotation task (LNRT), a common visual imagery task. Only participants whose behavioural performance on the HRT suggested use of a MI strategy were included in group comparisons. Young adults with DCD were significantly less efficient compared to controls when completing the HRT yet showed comparable performance on the LNRT relative to adults with typical motor ability. Our data are consistent with the view that atypical HRT performance in adults with DCD is likely to be attributed to specific difficulties engaging in MI, as opposed to deficits in general mental rotation. Based on the theory that MI provides insight into the integrity of internal action representations, these findings offer further support for the internal modelling deficit hypothesis of DCD.
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Discapacidades del Desarrollo/fisiopatología , Mano/fisiología , Imaginación , Trastornos de la Destreza Motora/fisiopatología , Adolescente , Adulto , Femenino , Humanos , Masculino , Destreza Motora , Desempeño Psicomotor , Análisis y Desempeño de Tareas , Adulto JovenRESUMEN
Previous studies investigating white matter organization in attention deficit hyperactivity disorder (ADHD) have adopted diffusion tensor imaging (DTI). However, attempts to derive pathophysiological models from this research have had limited success, possibly reflecting limitations of the DTI method. This study investigated the organization of white matter tracts in ADHD using fixel based analysis (FBA), a fiber specific analysis framework that is well placed to provide novel insights into the pathophysiology of ADHD. High angular diffusion weighted imaging and clinical data were collected in a large paediatric cohort (N = 144; 76 with ADHD; age range 9-11 years). White matter tractography and FBA were performed across 14 white matter tracts. Permutation based inference testing (using FBA derived measures of fiber density and morphology) assessed differences in white matter tract profiles between children with and without ADHD. Analysis further examined the association between white matter properties and ADHD symptom severity. Relative to controls, children with ADHD showed reduced white matter connectivity along association and projection pathways considered critical to behavioral control and motor function. Increased ADHD symptom severity was associated with reduced white matter organization in fronto-pontine fibers projecting to and from the supplementary motor area. Providing novel insight into the neurobiological foundations of ADHD, this is the first research to uncover fiber specific white matter alterations across a comprehensive set of white matter tracts in ADHD using FBA. Findings inform pathophysiological models of ADHD and hold great promise for the consistent identification and systematic replication of brain differences in this disorder.
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Trastorno por Déficit de Atención con Hiperactividad , Sustancia Blanca , Encéfalo/diagnóstico por imagen , Niño , Imagen de Difusión por Resonancia Magnética , Imagen de Difusión Tensora , Humanos , Sustancia Blanca/diagnóstico por imagenRESUMEN
Recent work in healthy adults suggests that white matter organization within the superior longitudinal fasciculus (SLF) may, at least partly, explain individual differences in fine motor skills. The SLF is also often implicated in the neurobiology underlying attention deficit hyperactivity disorder (ADHD) as part of the attention network connecting frontal and parietal regions. While ADHD is primarily characterized by inattention, impulsivity and/or hyperactivity, atypical fine motor control is a common comorbid feature. This study aimed to investigate the association between reduced fine motor skills in ADHD and microstructural properties within the SLF. Participants were 55 right-handed children with ADHD and 61 controls aged 9-11 years. Fine motor control was assessed using the Grooved Pegboard task. Children underwent high angular resolution diffusion MRI. Following pre-processing, constrained spherical deconvolution tractography was performed to delineate the three SLF branches bilaterally. Children with ADHD showed significantly poorer fine motor performance relative to controls in the non-dominant hand, indicated by significantly slower left handed Grooved Pegboard task performance. This slower response time for the non-dominant (left) hand was significantly associated with reduced apparent fibre density within the right SLF I, and reduced right SLF I, II and III volume. This finding was independent of spatial attention performance. These data support previous reports indicating that children with ADHD have poorer fine motor performance than controls in their non-dominant hand, and indicates that the neurobiological basis for impaired fine motor control may involve white matter properties within the contralateral SLF. This suggests that white matter properties in fronto-parietal areas may have broader implications than attention.