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

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

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.