Monosynaptic Reflexes and Preprogrammed Reactions in Down Syndrome: A Surface Electromyographic Study

The development of motor control in people affected by motor and cognitive pathologies leads to different behaviors in approaching everyday life activities. Understanding the origin of the differences in motor control between people with Down syndrome and those typically developing is very important for the definition of early and late intervention in rehabilitation. The aim of this study was to explore the stretch reflex and preprogrammed reactions as the origin of motor control development in a population of participants with Down syndrome. Eight subjects with Down syndrome (5 males, 3 females; mean age 23.11 ± 8.96) and 21 typically developing persons (7 males, 14 females; mean age 28.95 ± 9.56) were evaluated. The participants were seated on a chair with their dominant arm flexed at approximately 90°. Holding the handle of a bucket in his/her dominant hand, the participant was told to maintain the position after an unexpected load perturbation, produced by throwing a weight inside the bucket. The evaluation of primitive mechanisms of motor control revealed that no basic abnormality was present in the early motor control mechanisms of subjects with Down syndrome. The results provide evidence to the hypothesis that peripheral control in Down syndrome is comparable to that of typically developing persons, permitting the development of motor control throughout their sensorial exploration of the external world. However, the difference in central nervous system structure between people with Down syndrome and controls could probably produce different shaping of the higher elaboration centers causing a delayed or a different neuromotor response.