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

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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


Awake vs asleep

Awake vs. Asleep


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


Functional neuroimaging of speech perception in infants

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)


Functional neuroimaging of speech perception in infants

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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