Mastery of manual skills: recent insights into typical and atypical development of manual ability

Impaired hand function has a big impact on activities of daily life, as we use our hands for self-care, play, work, gestures, and writing, for instance. Typically, arm and hand mobility is characterized by a large repertoire of possibilities, allowing for great flexibility and the ability to adapt to environmental constraints. This amazing capacity to adjust is mediated by complex neural control. Gradually, our understanding of typical development of manual ability has increased. Likewise, our knowledge of the mechanisms involved in impaired hand mobility in children with a developmental motor disorder, such as cerebral palsy (CP) and developmental coordination disorder (DCD), has improved. In April 2012, a workshop was organized in Groningen which dealt with typical and atypical development of manual ability. Experts on neural mechanisms involved in typical and atypical development of eye–hand coordination discussed their recent research findings and the putative value of the new insights for diagnostics and intervention. This special supplement to Developmental Medicine & Child Neurology is the product of that venture. The first paper, by Arend Bos and colleagues, addresses the high prevalence of impaired fine motor skills in children born preterm. They especially review the aetiological factors that play a role in the impaired manual abilities of preterm children. The review suggests that intrauterine growth restriction, inflammatory conditions, and bronchopulmonary dysplasia treated with dexamethasone play an important role. The second paper, by Mijna Hadders-Algra, draws attention to the interrelationships between the development of reaching and that of postural control. In infants with developmental disorders, postural control is virtually always affected, which in turn affects the development of upper limb activities. The next four papers deal with the role of vision in manual activities. First, Melvyn Goodale reviews the evidence that the visual control of skilled, goal-directed movements requires transformations of visual information that differ from those required for visual perception. He argues that the so-called dorsal visual stream of the cerebral cortex is involved with visuomotor behaviour, whereas the ventral visual stream mediates conscious perception of the world. Oliver Braddick and Janette Atkinson follow with a paper that highlights the role of visuomotor information of the dorsal stream in typical development of manual skills. They hypothesize that ‘dorsal stream vulnerability’ is a widespread feature of neurodevelopmental disorders. This dorsal stream vulnerability could be one of the mechanisms underlying the high prevalence of fine motor impairment in preterm children. However, the review of Koen Van Braeckel and Gerry Taylor suggests that the impaired manual abilities of preterm children may also be caused by cerebellar dysfunction, as the cerebellum is critically involved in visuomotor function and is vulnerable to perinatal adversities. The paper of Andrea Guzzetta and colleagues also deals with the visual capacities of preterm infants. It reviews the evidence available of neural plasticity after periventricular infarction involving the optic radiations. The next section of five papers discuss aspects of manual abilities in children with CP. Kathleen Friel et al. discuss animal experiments that provide insight into typical and atypical development of the corticospinal tract. They highlight the role of activity-dependent synaptic competition in the initially bilateral corticospinal connections. They also discuss several experimental strategies for restoring a more normal pattern of corticospinal connections after an early unilateral lesion of the brain. Andrew Gordon and colleagues present a review of the sensory and motor deficits, including the more complex impairments in sensorimotor integration, motor planning and execution, and bimanual coordination, in children with unilateral spastic CP. They discuss the variety of pathophysiological mechanisms that may play a role. They suggest that the specific pathophysiology of a child may predict outcome of treatment. Geert Savelsbergh et al. discuss the role of vision in manual activities of children with unilateral spastic CP and provide suggestions how this knowledge may be applied in intervention. The last two papers in this section present evidence available for two specific approaches for intervention in children with CP. Bert Steenbergen et al. review current knowledge on the applicability of motor imagery in children with CP. Eva Brogren Carlberg and Kristina L€ owing report a systematic review of the effect of goal-setting in treatment of children with CP. The review did not provide support for a positive effect of goal-setting per se on treatment outcome. However, the authors stress that families, children, and therapists generally appreciate goal-setting. The last section of this special issue discusses various aspects of DCD. First, John Cairney and Scott Veldhuizen discuss the relationship between DCD and inactivity, poor fitness, and obesity. The next two papers discuss the neural substrate of DCD and paediatric dysgraphia by means of systematic reviews of the neuroimaging studies available. Lieke Peters et al. conclude that multiple brain areas are involved in the pathophysiology of DCD. Jessika van Hoorn and colleagues report that the limited data on the neural substrate of paediatric dysgraphia suggest that some children with dysgraphia have dysfunctions in extensive supraspinal networks, whereas in others dysfunction may be restricted to either the cerebellum or specific cortical sites. The last paper by Bouwien Smits-Engelsman and Peter Wilson discusses the variability in motor performance of children with DCD. They hypothesize that these children may have excessive neural noise in the motor system, which, in turn, may hamper accurate sensorimotor prediction. The papers in this special issue indicate the keen interest of neuroscientists and clinicians in vulnerability and plasticity of the young brain involved in visuomotor functions and manual abilities. They demonstrate that our knowledge increases and more often is translated into clues for intervention in children with developmental motor disorders. Nevertheless, there is still much to discover before we understand all factors playing a role in vulnerability and resilience in motor development. To achieve this ultimate goal, interdisciplinary translational research is needed, where animal research is paired to studies in humans, and studies that use brain imaging techniques are matched with studies in