Inhibition of the eyeblink reflex in the human infant

In human adults the eyeblink elicited by a given stimulus can be inhibited if that stimulus is preceded by another stimulus at an appropriate lead interval. In the present work, pairs of eyeblink-eliciting stimuli separated by 300-1200 msec were presented to sleeping preterm and full-term infants as well as to adults. Preterm infants did not exhibit reliable inhibition at any interval. Full-term infants did so, but they required longer interstimulus intervals than were needed for inhibition in the adult subjects. Results imply that the neural systems that mediate reflex inhibition are functional at birth, but that they are relatively slow to act.