Developmental and white matter correlates of word learning

Context

Vocabulary acquisition has been linked to a neurocognitive model of memory consolidation, in which novel spoken words are stored rapidly in a medial temporal system, with sleep updating neocortical systems. However, current models do not take neural maturation into account and preliminary evidence suggests a different weighting of the mechanisms that support word learning across development. Notably, sleep in pre/early adolescence may be better architectured for consolidation than in adulthood (owing to larger amounts of slow-wave sleep). Furthermore, whilst significant knowledge is accumulating about the neural mechanisms of sleep-associated consolidation, how these mechanisms interact with the structural properties of the developing language network remains unclear.

The research

We examined whether children aged 10 to 12 years can outperform adults’ consolidation of newly learned words over a nap. Both age groups learned new words and then spent roughly 90 minutes either awake or asleep in the sleep lab whilst undergoing polysomnography recording.

Both groups showed memory benefits for the new words after a nap than after wake, and children showed greater benefits than adults (as well as showing double the amount of slow-wave sleep).

Using magnetic resonance imaging (MRI)/diffusion tensor imaging (DTI), we are also examining how children’s memory for the new words is associated with white matter integrity in three tracts key to language: arcuate fasciculus, uncinate fasciculus and superior longitudinal fasciculus.

Preliminary results suggest that integrity within these tracts indeed plays a role in the initial learning of new words, and importantly also children’s ability to consolidate them during a nap. These data emphasise the importance of developmental and MRI/DTI data for advancing neurocognitive models of memory.

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