title: Cerebral responses to infant-directed speech and the effect of talker familiarity.
abstract: A number of behavioral studies suggest that infant-directed speech (IDS) plays a more important role in facilitating both: a) speech perception, and b) adult-infant social interactions than does adult-directed speech (ADS), and hence that IDS contributes to subsequent social and language development. However neural substrates that may underlie these IDS functions have not been examined. The present study examined cerebral hemodynamic responses to IDS in 48 infants (4-13 months of age) using near-infrared spectroscopy (NIRS). Japanese sentences uttered by the infants' own mothers and by unfamiliar mothers were used to record activations in temporal and frontal area separately. Increased activations were observed predominantly in infants' left and right temporal areas when they listened to IDS rather than to ADS when both involved voices of their own and unfamiliar mothers. In contrast, significantly greater activations were observed in the frontal area when infants listened to IDS produced by their own mothers, not when IDS arose from unfamiliar mothers. Furthermore, the present results indicate that responses to IDS do vary as a function of the infant's age and the talker familiarity. These findings suggest a differential function for frontal and temporal areas in processing infant-directed speech by the different speakers.
authors.affiliation: Department of Psychology, Keio University, 2-15-45 Mita, Minato-ku, Tokyo 108-8345, Japan. nnaoi@educ.kyoto-u.ac.jp
authors.forename: Nozomi
authors.initials: N
authors.lastname: Naoi
authors.forename: Yasuyo
authors.initials: Y
authors.lastname: Minagawa-Kawai
authors.forename: Ai
authors.initials: A
authors.lastname: Kobayashi
authors.forename: Koji
authors.initials: K
authors.lastname: Takeuchi
authors.forename: Katsuki
authors.initials: K
authors.lastname: Nakamura
authors.forename: Jun-Ichi
authors.initials: J
authors.lastname: Yamamoto
authors.forename: Shozo
authors.initials: S
authors.lastname: Kojima
mesh_terms: D001931:Brain Mapping; D005260:Female; D005625:Frontal Lobe / Q000502:physiology*; D006801:Humans; D007223:Infant; D007804:Language Development; D008297:Male; D009034:Mother-Child Relations; D009035:Mothers; D013067:Speech Perception / Q000502:physiology*; D013702:Temporal Lobe / Q000502:physiology*