Development of lateralised speech perception: Brain activation in 4-month-olds and adults
2008 (English)In: Papers from the first Birgit Rausing Language Program Conference in Linguistics, Lund, June 2008 / [ed] Kai-Uwe Alter, Lund: Centre for Languages and Literature, Lund University , 2008, 45-46 p.Conference paper (Other academic)
Previous fMRI and PET studies indicated left hemispheric activation for the processing of speech and phonetic features, and right hemispheric activation for the processing of emotions and melody. EEG measures are not commonly employed in lateralisation research, neither has lateralisation been extensively investigated in a developmental perspective. This study aims to fill this gap. Although ERP measures cannot precisely localize task-activated cortical regions, differences in voltage reflect scalp electricity in response to the activation of a distinct neural network (Giard et al., 1995). With EEG, we study the lateralisation of speech processing in 4- and 9-month-olds and adults in two conditions, spoken sentences and their spectrally rotated version. Rotating is a technique to render speech intelligible while preserving language-specific characteristics such as rhythm. A previous EEG study showed no lateralisation in 4-month-olds for the processing of speech versus nonspeech sounds as measured with 65 electrodes (Dehaene-Lambertz, 2000). For refined measurement, we employ 128 electrodes and use infant-directed speech stimuli for both conditions. It has been established that language comprehension tasks elicit bilateral hemispheric activation (Awad, Warren, Scott, Turkheimer, & Wise, 2007; Davis et al., 2007), showing intrahemispheric localisation differences within the left hemisphere for phonetic features and comprehension in speech processing tasks (Obleser, Zimmermann, Van Meter, & Rauschecker, 2007; Scott, Blank, Rosen, & Wise, 2000). As sentence comprehension increases with age, we predict an increase of activation in the left hemisphere when comparing 4- to 9-month-olds and 9-month-olds to adults. The melodic and emotional components of the infant-directed speech stimuli should elicit right-hemispheric activation which is predicted to decrease with age. Therefore, the measured differences between left- and right-hemispheric activation are predicted to increase with age. Left-hemispheric activation is also expected for the rotated speech condition due to the speech-likeness of the stimuli, however to a lesser degree than in the natural sentence condition (Ischebeck, Friederici, & Alter, 2007). This activation difference between the speech and rotated speech conditions should also increase with age as comprehension increases. The results are presented in regard to these hypotheses and discussed in the light of recent research.
Place, publisher, year, edition, pages
Lund: Centre for Languages and Literature, Lund University , 2008. 45-46 p.
Humanities General Language Studies and Linguistics
IdentifiersURN: urn:nbn:se:su:diva-17421ISBN: 978-91-633-5561-5OAI: oai:DiVA.org:su-17421DiVA: diva2:183942
Brain Talk: Discourse with and in the brain. The first Birgit Rausing Language Program Conference in Linguistics, Lund, June 2008