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Reduced Slow-wave Sleep in Dyslexia may Explain Differences in Language Consolidation
Poster Session B, Wednesday, September 30, 4:30 - 6:30 pm, Wangari Maathai
Tali Bitan1,2, Eva Kimel1,3, Ilana S Hairston4, Anat Prior1, Gareth Gaskell3, Lisa Henderson3, Daphna Ben-Zion1, Yekete Akal4; 1University of Haifa, Israel, 2University of Toronto, Canada, 3University of York, UK, 4Tel-Hai Academic College, Israel
Language learning continues offline after exposure, with sleep playing an active role in memory consolidation. Adults with dyslexia - a congenital, permanent reading difficulty - also have reduced vocabularies and exhibit less efficient learning of linguistic regularities. Less efficient sleep-dependent memory consolidation could contribute to these difficulties. Here we test this by assessing the acquisition of a small artificial language, followed by one full-night EEG recording (polysomnography). Participants (N_Controls = 29; N_Dyslexia = 21) learned novel vocabulary words in the evening, presented at high or low frequency, and also learned their plural inflections, with embedded morpho-phonological regularities. We examined the temporal dynamics of maintaining this knowledge across nine days (tested on days 1,2,3, and 9), and the associations between performance and two sleep metrics: sleep spindles and slow-wave sleep duration - both previously linked to vocabulary consolidation. We found reduced slow-wave sleep duration, and overall lower performance in both vocabulary learning and generalisation in the dyslexia group. Overall, vocabulary accuracy improved across the first night following learning, and the change was positively associated with slow-wave sleep percentage. Memory for infrequent words declined by Day-9 as compared to Day-3, but greater spindle density during the first night was associated with a smaller decline. Accuracy in generalising the regularity of plural inflections also increased across the first night but showed no correlations with sleep metrics. These results demonstrate that vocabulary and regularity learning show different temporal dynamics of consolidation and distinct patterns of association with sleep metrics, with both spindles and slow-wave sleep contributing to vocabulary acquisition and long term maintenance, but not to generalisation. In dyslexia, these benefits may be attenuated over the long term due to reduced slow wave sleep.
Topic Areas: Disorders: Developmental, Language Development/Acquisition