OS_17. Language acquisition
Saturday, October 01st, 2011 [10:50 - 11:50]
OS_17. 1 - Functional neuroimaging language profiles modeled with distributed sources
Diaz, J. & Mesa, I.
CEIT. San Sebastian, Spain.
For several years, researchers have been working on assessing hemispheric dominance for receptive language by using magnetoencephalography. As a result, a normative analysis for deriving brain activation profiles from single dipole models has been established. The main objectives of this study are 1) to perform a normative analysis of language profiles estimating distributed sources of brain activity and 2) to compare this analysis with other performed using single dipoles. Thus, a large sample of individuals were analyzed to observe if the features vary with stimulus presentation parameters, including the modality of presentation, task characteristics, or by the age or gender of the participants; and if the features happen to be similar to the ones found in single dipole models. For auditory tasks, as with single dipole models, the profile of activity detected in the middle temporal gyrus and perisylvian regions were consistently higher than the rest of the regions. For visual tasks, on the contrary, the perisylvian region happened to be low activated. Regarding the language lateralization, as the single dipole model, for the later components (>150ms) the activity found in the left temporal lobe is higher than in the right, but on the contrary, no statistical significance was found.
OS_17.2 - Phonological features in lexical activation: Graded effects in adults and toddlers
Altvater-Mackensen, N. & Mani, N.
University of Göttingen
Several models of word recognition assume that lexical representations are organized in terms of phonological features. The present study investigates whether lexical activation in adults and toddlers can be modulated by the degree of feature overlap between two words. Using the visual world paradigm, 32 German adults were presented with four images on a screen. Labels of two images, i.e., target and distracter, rhymed but differed in the degree of feature overlap on the initial consonant (1, 2 or 3 feature difference). Similarly, 24 German 24-month-olds were presented with a prime image, followed by simultaneous presentation of a target and distracter image. Again, prime and target labels rhymed but differed in the degree of feature overlap on the initial consonant (2 or 3 features difference). We then measured how fast subjects oriented towards the target upon hearing the target label, and how long they looked at the target image. Results show graded effects of target recognition- the amount of time spent looking at the target varied with increasing feature difference in both adults and toddlers. This suggests that, in the developing as well as the mature lexicon, phonological features, and not just phonemes, influence lexical activation of phonologically similar words.
OS_17.3 - Novel word learning is associated with sleep in children
Henderson, L. 1 , Weighall, A. 2 & Gaskell, G. 1
1 University of York
2 Sheffield Hallam University
Although the acquisition of a novel spoken form is often rapid, previous research on adults suggests that integration of novel and existing knowledge (measured by engagement in lexical competition) requires a consolidation period associated with sleep. These findings are well-explained by neural models of learning in which sleep provides an opportunity for hippocampal information to be fed into long-term neocortical memory. It remains unclear whether this time-course dissociation characterises word learning in children. Fifty-three children (7 - 12 years) were exposed to novel competitor words at 07:30-09:30 (AM Group) or 17:30-19:30 (PM Group). Whilst children were able to recognise and recall some novel words immediately after exposure, performance improved significantly after sleep (at the 12-hr retest for the PM Group and the 24-hr retest for the AM Group) and remained good 8 days later. Similarly, novel words only induced competition effects after a period of sleep (rather than wake). These findings suggest that children utilize a dual-memory system in the acquisition and integration of vocabulary. Since previous research into vocabulary acquisition in children has largely focused on the immediate consequences of word learning, the present data call for a shift in our conception of vocabulary acquisition in development.