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
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
• 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
20s Silence 20s Silence
20s of forward speech
20s of backward speech
20 healthy, non-sedated infants (2-3mo)Speech = highly intonated female voice; in French
Hypothesis
• Forward speech = ↑ activation than backward speech
• Fast temporal auditory transitions and phonetic information will be jointly activated
Activation to Sound
• Similar to adults
Brain Lateralization
• Similar to adults
Forward Speech vs. Backward Speech
• In adults, the area is left superior temporal sulcus
Awake vs. Asleep
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?
• 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
• 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
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.