Infants' brain responses to speech suggest analysis by synthesis.

Bibliographic Collection: 
APE, CARTA-Inspired Publication
Publication Type: Journal Article
Authors: Kuhl, Patricia K; Ramírez, Rey R; Bosseler, Alexis; Lin, Jo-Fu Lotus; Imada, Toshiaki
Year of Publication: 2014
Journal: Proc Natl Acad Sci U S A
Volume: 111
Issue: 31
Number: 31
Pagination: 11238-45
Date Published: 2014 Aug 5
Publication Language: eng
ISBN Number: 0027-8424
ISSN: 1091-6490
Accession Number: 25024207
Keywords: Adult, Algorithms, Auditory Perception, Brain, Frontal Lobe, Humans, Infant, Language, Magnetoencephalography, Motor Cortex, Speech, Speech Perception, Temporal Lobe

Historic theories of speech perception (Motor Theory and Analysis by Synthesis) invoked listeners' knowledge of speech production to explain speech perception. Neuroimaging data show that adult listeners activate motor brain areas during speech perception. In two experiments using magnetoencephalography (MEG), we investigated motor brain activation, as well as auditory brain activation, during discrimination of native and nonnative syllables in infants at two ages that straddle the developmental transition from language-universal to language-specific speech perception. Adults are also tested in Exp. 1. MEG data revealed that 7-mo-old infants activate auditory (superior temporal) as well as motor brain areas (Broca's area, cerebellum) in response to speech, and equivalently for native and nonnative syllables. However, in 11- and 12-mo-old infants, native speech activates auditory brain areas to a greater degree than nonnative, whereas nonnative speech activates motor brain areas to a greater degree than native speech. This double dissociation in 11- to 12-mo-old infants matches the pattern of results obtained in adult listeners. Our infant data are consistent with Analysis by Synthesis: auditory analysis of speech is coupled with synthesis of the motor plans necessary to produce the speech signal. The findings have implications for: (i) perception-action theories of speech perception, (ii) the impact of "motherese" on early language learning, and (iii) the "social-gating" hypothesis and humans' development of social understanding.

DOI: 10.1073/pnas.1410963111
Alternate Journal: Proc. Natl. Acad. Sci. U.S.A.