[Postactivational changes in the reflex excitability of the motoneuronal apparatus of the spinal cord in newborn infants].

In 16 newborn infants ageing from several hours to 6 days, by means of paired stimulation, studies have been made on postactivational recovery of the reflex excitability of spinal motoneuronal apparatus. It was shown that early phases of the recovery cycle (early facilitation and depression) are similar in all the infants studied and do not significantly alter with age, whereas later phases within the first days of life follow two types. The first type is characterized by the intensive secondary facilitation which is transformed into exaltation, late depression being absent. The second type is characterized by low level of facilitation and the presence of depression. To the 4-5th day, the recovery cycle attains the pattern similar to that in adults. It is suggested that age changes of the recovery cycle reflect both functional maturation of the structures which are involved into the organization of postactivational changes of motoneuronal apparatus, and the dynamics of metabolism in newborns.