Parietal and cerebellar control of reaching and grasping and its dysfunction in developmental coordination disorder

手眼协调有发育障碍的儿童可能需要比正常发育儿童更长的时间来学习系鞋带、接球或写字。大约每20个孩子中就有一个会在日常运动任务中表现出极大的困难，以至于干扰了他们的学业，削弱了他们参与运动的能力和愿望，并降低了他们的总体生活满意度。这类儿童据说患有发育协调障碍(DCD)，这种情况曾被称为“笨拙”。到目前为止，尽管人们对发育障碍的研究越来越感兴趣，但我们还不知道大脑的哪一部分(或哪些部分)在这种障碍中受到影响，以及这些脑区的生长和发育可能如何与儿童系鞋带、接球或清晰书写的能力有关。这项研究项目将检验一种假设，即负责快速分析感觉信息和运动信号以及负责眼手协调的大脑区域在DCD儿童中受到损害。与我们身体时刻协调有关的最重要的大脑区域是小脑，也就是“小脑”。小脑位于脊髓的顶端和头部的后部，接受数亿次输入，并对其进行处理，然后将信号发送到脊髓以控制身体，并返回到大脑以反馈身体现在正在做的事情。小脑最擅长的一个例子是当你在一块冰上滑倒时会发生什么--一只脚突然突然向前突起，但你身体的其他部分僵硬和紧张，你的手臂抽出，你的身体扭曲，但不知何故你保持了站立！所有这些大脑对信息的超快处理都发生在你甚至意识到脚下的冰之前。小脑是身体和大脑之间的守门人，过滤和平滑，阻止并允许大脑的命令到达身体。对于非常精细或非常快速的运动控制，小脑是不可或缺的。通过在医用脑扫描仪中拍摄小脑和大脑其他部分的大量图像，我们将能够将小脑的大小、健康和连通性与人们进行快速手眼协调运动的能力联系起来，这种能力在DCD中受到了损害。除了大脑录音，我们还将要求成年人和儿童向前伸手，抓住一个发光的乒乓球。有时，就在他们开始伸手拿球后，我们会关掉球内的灯，并点燃几厘米外的另一个球。问题是：在光线在第一个和第二个球之间切换后，成年人，以及患有和不患有DCD的儿童，可以多快地移动他们的手来抓住第二个球？在之前的研究中，人们被证明在0.1秒内就能在两个球之间切换手部动作--这与在奥运会赛跑或游泳比赛中导致“错误起跑”的时间相同。这表明，当我们做出伸展运动时，可以说，我们的大脑领先我们一步--它正在预测我们的手应该在哪里，并在我们意识到物体已经移动之前非常迅速地调整我们的手的动作。DCD研究的长期目标是发现行为、药物或其他治疗方法，以改善数十万儿童的运动协调。通过帮助确定涉及的潜在回路，并准确定位DCD功能障碍的发育部位，该项目将在实现这一目标方面发挥重要作用。

Children with developmental difficulties in hand-eye coordination may take longer than typically developing children to learn to tie their shoelaces, to catch a ball, or to write legibly. Around 1 in 20 children will show such great difficulty in everyday movement tasks that it interferes with their school-work, impairs their ability and desire to participate in sports, and lowers their overall life-satisfaction. Such children are said to have developmental coordination disorder (DCD), a condition that might once have been known as 'clumsiness'. As yet, despite a growing interest in studying developmental disorders, we do not yet know which part (or parts) of the brain is affected in this disorder, and how the growth and development of such brain areas may relate to the child's ability to tie their shoelaces, catch balls, or write legibly.This research project will test the hypothesis that the brain areas responsible for the rapid analysis of sensory information and movement signals, and for eye-hand coordination, are damaged in children with DCD. The most important brain region involved in the coordination of our body from moment to moment is the cerebellum, or 'little brain'. Sitting at the top of the spinal cord, and at the back of the head, the cerebellum receives hundreds of millions of inputs, and processes them before sending signals to the spinal cord to control the body, and back up to the brain to feed back what the body is now doing. One good example of what the cerebellum may do best is what happens when you slip on a patch of ice - one foot suddenly lunges forward unexpectedly, but the rest of your body stiffens and tenses, your arms jerk out, your body twists, but somehow you stay standing up! All of this super-rapid processing of information by the brain happens before you are even aware of the ice underfoot. The cerebellum is the gate-keeper between the body and the brain, filtering and smoothing, blocking and permitting the brain's commands to reach the body. For the very fine, or the very fast control of movement, the cerebellum is indispensable.By taking a number of images of the cerebellum and the rest of the brain in a medical brain scanner, we will be able to link the size, health, and connectivity of the cerebellum with people's ability to make the kinds of rapid hand-eye-coordination movements that are impaired in DCD. As well as taking brain recordings, we will also ask adults and children to reach forwards and grasp an illuminated ping-pong ball. Sometimes, just after they start to reach for the ball, we will turn off the light inside the ball, and light up another ball just a few centimetres away. The question is: after the light has switched between the first and second balls, how quickly can adults, and children with and without DCD, move their hand to grab the second ball? In previous studies, people have been shown to switch their hand movements between the two balls in just 0.1 seconds - the same amount of time that would cause a 'false start' in an Olympic running or swimming event. This suggests that, while we are making a reaching movement our brain is, so to speak, one step ahead of us - that it is predicting where our hand should be, and very rapidly adjusting our hand movements before we are even aware that the object has moved.The long-term goal in DCD research is to discover behavioural, pharmacological, or other treatments to improve the motor coordination of hundreds of thousands of children. By helping to identify the underlying circuits involved, and pinpointing the sites of dysfunctional development in DCD, this project will play an important role in achieving that goal.