The maturation of cutaneous reflexes studied in the upper limb in man.

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Abstract
Cutaneous reflex responses were recorded from forearm flexor and extensor muscles following electrical stimulation of the fingers. Recordings were made from premature infants, term infants and children between the age of 6 wk and 11 yr. In the newborn, stimulation of the fingers elicits such a powerful reflex that individual stimuli will evoke a reflex synchronous action potential in both forearm flexor and extensor muscles. Individual stimuli delivered to the fingers also elicit reflex synchronous muscle action potentials in forearm flexor and extensor muscles in patients with clinical signs of upper motor neuron lesion affecting the upper limb; this was not observed in normal adult subjects. The latency of the reflex response in the term infant is .apprx. 18 ms. Comparison of this value with the latency of the tendon jerk for these muscles would indicate a central delay for the cutaneous reflex of .apprx. 3 ms. The latencies of the cutaneous reflex and tendon jerk rmeain constant over the first 5 yr of life. The size of the short-latency cutaneous reflex response deceases progressively over the 1st yr of life. In the 2nd yr of life stimulation of the fingers produces long as well as short-latency increases in recorded muscle electrical activity. The maturation of the cutaneous reflex response is discussed in terms of the maturation of the function of the corticospinal tract.