Functional neuroimaging of speech perception in infants
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Functional Neuroimaging of Speech Perception in Infants. Dehaene-Lambertz , G. , Dehaene S., and Hertz-Pannier, L. By Divya Patel. Why study infants?. Adult human brain: anatomical and functional specialization for speech processing How? clarify how it emerges through development.

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Functional neuroimaging of speech perception in infants

Functional Neuroimaging of Speech Perception in Infants

Dehaene-Lambertz, G. , Dehaene S., and Hertz-Pannier, L.

By Divya Patel


Why study infants
Why study infants?

  • Adult human brain: anatomical and functional specialization for speech processing

  • How?

    • clarify how it emerges through development


Language and infants
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


Motivation
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


Experimental design
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


Hypothesis
Hypothesis

  • Forward speech = ↑ activation than backward speech

  • Fast temporal auditory transitions and phonetic information will be jointly activated


Activation to sound
Activation to Sound

  • Similar to adults


Brain lateralization
Brain Lateralization

  • Similar to adults


Forward speech vs backward speech
Forward Speech vs. Backward Speech

  • In adults, the area is left superior temporal sulcus



Was the hypothesis supported
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


Other underlying mechanisms
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


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


Future directions
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)


QUESTIONS?

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


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