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Functional Neuroimaging of Speech Perception in Infants

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  1. Functional Neuroimaging of Speech Perception in Infants Dehaene-Lambertz, G. , Dehaene S., and Hertz-Pannier, L. By Divya Patel

  2. Why study infants? • Adult human brain: anatomical and functional specialization for speech processing • How? • clarify how it emerges through development

  3. Language and infants? • Considerable language takes place in the 1st year • Development in: • Phonology: organization of sounds • Prosody: tone of voice, rhythm • Word segmentation: when a word starts/ends

  4. Motivation • Not much known about brain mechanisms • Studies mostly use ERPs • Great  know temporal lobes contain neural circuit for phoneme discrimination • Not as great  do not provide spatial information • This study uses fMRI

  5. Experimental Design 20 healthy, non-sedated infants (2-3mo) Speech = highly intonated female voice; in French 20s of forward speech 20s of backward speech 20s Silence 20s Silence

  6. Hypothesis • Forward speech = ↑ activation than backward speech • Fast temporal auditory transitions and phonetic information will be jointly activated

  7. Activation to Sound • Similar to adults

  8. Brain Lateralization • Similar to adults

  9. Forward Speech vs. Backward Speech • In adults, the area is left superior temporal sulcus

  10. Awake vs. Asleep

  11. Was the hypothesis supported? • Forward speech = ↑ activation than backward speech in left angular gyrus and left mesial parietal lobe • Fast temporal auditory transitions and phonetic information will be jointly activated in left temporal lobe • From superior temporal gyrus to surrounding areas of superior temporal sulcus Yes

  12. Other underlying mechanisms? • In adults: • Precuneus and dorsolateral PFC (dlPFC) activated during retrieval • In infants: • Precuneus and dlPFC activated • May indicate early engagement of active memory retrieval mechanism Yes, there seems to be

  13. Strengths Limitations Not enough background Assumed all readers would know basic infant brain development • Approaches were different than prior studies • Used fMRI • Used non-sedated babies • Very straight forward • Images corresponding to brain parts

  14. Future Directions • It would be interesting to do a longitudinal study, to understand when exactly the changes take place • To create a study where retrieval can be tested, perhaps through habituation • To find specific evidence for either • nativist view (language mechanisms are innate) • interactionist view (language mechanisms are developed through interaction)

  15. QUESTIONS? Dehaene-Lambertz G, Dehaene S, Hertz-Pannier L. (2002) Functional neuroimaging of speech perception in infants. Science 298(5600):2013-5.