Motor Overflow in Nonretarded Children and Down Syndrome Adults

Abstract

<p> Two experiments are reported that examine motor overflow in Down syndrome and nonretarded persons. The two main purposes of the experiments were to determine the utility of motor overflow as a diagnostic tool and the relationship between motor overflow and transfer of training. In Experiment 1, nonretarded children and adults performed a unimanual finger-sequencing task. It was found that motor overflow follows a developmental course. As well, a positive relationship was found between motor overflow and intermanual transfer of training, and children were able to reduce their ipsilateral motor overflow with training. These results indicate that caution should be taken in diagnosing central nervous system dysfunction of a structural nature using motor overflow. In Experiment 2, similar procedures were used to examine younger children and Down syndrome adults. It was found that with conscious effort, even the children could reduce their motor overflow. A positive relationship between transfer of training and motor overflow was also evidenced in Down syndrome subjects. As well, there was greater transfer of training from the left hand to the right hand than the reverse, in both Down syndrome adults and young, nonretarded children. These findings are discussed in reference to factors affecting the appearance of motor overflow and what can be learned about cerebral specialization in nonretarded and special populations.</p>