Optical brain imaging reveals general auditory and language-specific processing in early infant development.
This study uses near-infrared spectroscopy in young infants in order to elucidate the nature of functional cerebral processing for speech. Previous imaging studies of infants' speech perception revealed left-lateralized responses to native language. However, it is unclear if these activations were due to language per se rather than to some low-level acoustic correlate of spoken language. Here we compare native (L1) and non-native (L2) languages with 3 different nonspeech conditions including emotional voices, monkey calls, and phase scrambled sounds that provide more stringent controls. Hemodynamic responses to these stimuli were measured in the temporal areas of Japanese 4 month-olds. The results show clear left-lateralized responses to speech, prominently to L1, as opposed to various activation patterns in the nonspeech conditions. Furthermore, implementing a new analysis method designed for infants, we discovered a slower hemodynamic time course in awake infants. Our results are largely explained by signal-driven auditory processing. However, stronger activations to L1 than to L2 indicate a language-specific neural factor that modulates these responses. This study is the first to discover a significantly higher sensitivity to L1 in 4 month-olds and reveals a neural precursor of the functional specialization for the higher cognitive network.
Minagawa-Kawai
Yasuyo
Y
Laboratoire de Sciences Cognitives et Psycholinguistique, ENS-DEC-EHESS-CNRS, Paris 75005, France. myasuyo@bea.hi-ho.ne.jp
van der Lely
Heather
H
Ramus
Franck
F
Sato
Yutaka
Y
Mazuka
Reiko
R
Dupoux
Emmanuel
E
D000161:Acoustic Stimulation / Q000379:methods; D001931:Brain Mapping; D002657:Child Development / Q000502:physiology*; D004644:Emotions / Q000502:physiology; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D007223:Infant; D007802:Language; D008297:Male; D009716:Numerical Analysis, Computer-Assisted; D011930:Reaction Time; D019265:Spectroscopy, Near-Infrared / Q000379:methods; D013067:Speech Perception / Q000502:physiology*; D013702:Temporal Lobe / Q000502:physiology*; D013997:Time Factors
D006454:Hemoglobins; C100003:deoxyhemoglobin