Lower limb cutaneous polysynaptic reflexes in the child, according to age and state of waking or sleeping.

An electromyographic study of reflex responses elicited by stimulation of an area of skin in the lower limb was undertaken in awake or sleeping children from 3 days to 3 years of age. Recordings were made on the tibialis anterior and the short head of the femoral biceps. In the awake child, electrical stimulation of the cutaneous area around the toes evoked polysynaptic discharges (R II and R III) in both muscles. From birth to one year of age, the threshold for the tibialis anterior was much lower than for the short head of biceps, and the flexion reflex pattern predominated. After 20 months of age, the recruitment pattern for polysynaptic responses was different: the threshold for tibialis anterior increased and became higher than for the short head of biceps, as in the adult. In sleeping children, the most striking feature was the depression of R II responses. In non-REM sleep, R III responses also were depressed, with a similar threshold in both muscles, and even disappeared during deep sleep. In REM sleep, R III responses were present in babies, but seemed to be abolished in older children.