Does the neonate's brain have left hemisphere (LH) dominance for speech? Twelve full-term neonates participated in an optical topography study designed to assess whether the neonate brain responds specifically to linguistic stimuli. Participants were tested with normal infant-directed speech, with the same utterances played in reverse and without auditory stimulation. We used a 24-channel optical topography device to assess changes in the concentration of total hemoglobin in response to auditory stimulation in 12 areas of the right hemisphere and 12 areas of the LH. We found that LH temporal areas showed significantly more activation when infants were exposed to normal speech than to backward speech or silence. We conclude that neonates are born with an LH superiority to process specific properties of speech.T wo models attempt to account for the origin of the lefthemisphere (LH) dominance for speech. The first model assumes that, at birth, the LH displays superiority in processing all acoustic signals (1). The second postulates that neonates are endowed with specific structures to processes speech signals in the LH (2). Both models assume an LH superiority at birth. However, only the second model postulates that the LH superiority is specific for speech and that it may be intrinsically related to the emergence of the language faculty. During development, the infant's brain grows and matures, and its functional organization changes, even if its gross anatomy displays striking similarities to that of the adult (3) from the start. The association of language with the LH may arise as a consequence of language acquisition, or, alternatively, this association may reflect an innate disposition of certain areas of the brain for language. Several behavioral studies have focused on this issue. One study (4) measured foot-kicking responses and observed behaviors that suggested an LH superiority for speech stimuli as compared with other auditory stimuli only hours after birth. Another study reported a right ear advantage for speech stimuli with 3-monthold infants by using the orienting response (5). An additional study used the nonnutritive sucking response to test 2-week-old infants and found a right ear advantage for speech but not for other auditory stimuli (6). A recent study with older infants reports that, as soon as babbling sets in, the mouth tends to rise toward the right side of the face, suggesting an underlying LH superiority. This asymmetry is absent during nonlinguistic vocal gestures (7). These behavioral studies suggest that speech stimuli presented to prelinguistic infants result in greater LH involvement and that an LH superiority is apparent as soon as the first language-like productions begin. Nonetheless, behavioral methods have limitations: neonates often fail to complete the tests because of fussing or crying. The advent of brain-imaging techniques has made it possible to test young infants even when they fail to make overt responses. Furthermore, imaging methods link behavioral observations to their...

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