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

在手眼协调方面有发育障碍的儿童可能比正常发育的儿童需要更长的时间来学习系鞋带，接球或书写清晰。大约每20个孩子中就有1个在日常运动任务中表现出极大的困难，这会干扰他们的学业，削弱他们参与运动的能力和愿望，并降低他们的整体生活满意度。据说这样的孩子患有发育协调障碍（DCD），这种情况曾经被称为“笨拙”。到目前为止，尽管人们对研究发育障碍的兴趣越来越大，但我们还不知道是哪一部分，在这种疾病中，大脑（或部分）受到影响，以及这些大脑区域的生长和发育如何与孩子系鞋带，接球，这项研究项目将测试一个假设，即负责快速分析感官信息的大脑区域，运动信号和眼手协调在患有DCD的儿童中受损。参与我们身体每时每刻协调的最重要的大脑区域是小脑，或“小大脑”。小脑位于脊髓的顶部，在头部的后部，它接收数亿个输入，并在将信号发送到脊髓以控制身体之前对其进行处理，然后返回到大脑以反馈身体正在做的事情。一个很好的例子是，当你在一片冰上滑倒时，小脑可能会做得最好--一只脚突然出乎意料地向前冲，但你身体的其他部分会僵硬和紧张，你的手臂会突然伸出，你的身体会扭曲，但不知何故，你会站起来！所有这些大脑对信息的超快速处理都发生在你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，阻止和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来说，小脑是必不可少的。通过在医学大脑扫描仪中拍摄小脑和大脑其他部分的图像，我们将能够将小脑的大小，健康和连接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中受损。除了记录大脑活动，我们还将要求成人和儿童向前伸手抓住一个发光的乒乓球。有时，就在他们开始伸手去拿球的时候，我们会关掉球里的灯，然后点亮几厘米外的另一个球。问题是：当灯光在第一个球和第二个球之间切换后，成年人和有或没有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，人们在两个球之间切换手部动作的时间仅为0.1秒--这段时间相当于奥运会跑步或游泳比赛中造成“抢跑”的时间。这表明，当我们做一个伸手的动作时，我们的大脑可以说比我们快一步--它预测我们的手应该在哪里，并且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来改善数十万儿童的运动协调性。通过帮助识别所涉及的潜在电路，并精确定位DCD中功能失调的发育部位，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.