Timing and force control deficits in clumsy children.

This study investigated the link between cognitive processes and neural structures involved in motor control. Children identified as clumsy through clinical assessment procedures were tested on tasks involving movement timing, perceptual timing, and force control. The clumsy children were divided into two groups: those with soft neurological signs associated with cerebellar dysfunction and those with soft neurological signs associated with dysfunction of the basal ganglia. A control group of age-matched children who did not exhibit evidence of clumsiness or soft neurological signs was also tested. The results showed a double dissociation between the two groups of clumsy children and the tests of timing and force. Clumsy children with cerebellar signs were more variable when attempting to tap a series of equal intervals. They were also more variable on the time perception task, indicating a deficit in motor and perceptual timing. The clumsy children with basal ganglia signs were unimpaired on the timing tasks. However, they were more variable in controlling the amplitude of isometric force pulses. These results support the hypothesis that the control of time and force are separate components of coordination and that these computations are dependent on different neural systems.