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

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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.