The ontogenetically earliest discriminative response of the human brain.

Speech sounds elicited electric brain responses in healthy premature infants born 30-35 weeks after conception, demonstrating that the human brain is able to discriminate speech sounds even at this early age, well before term, and supporting previous results suggesting that the human fetus may learn to discriminate sounds while still in the womb. We presented preterm infants with stimulus sequences consisting of a repetitive vowel that was occasionally replaced by a different vowel. This infrequent vowel elicited a response resembling the adult mismatch negativity, which is known to reflect the brain's automatic detection of stimulus change. The present results constitute the ontogenetically earliest discriminative response of the human brain ever recorded.