SPRING 2025 NO.92 / THOUGHT LEADERSHIP BRIEF 2 Accuracy rate 1.0 0.9 0.8 0.7 Post-test 1 (before sleep) Full-night sleep *** Post-test 2 (after sleep) Learning a new language may improve brain plasticity, which refers to the brain’s ability to adapt and reorganize itself in response to new information. Language learning plays a crucial role in delaying the progression of neurodegenerative diseases by stimulating brain plasticity, thereby enhancing quality of life and fostering healthy ageing. Additionally, sleep contributes significantly to facilitating language learning. Newly learned information can be preserved better through memory consolidation during overnight sleep. However, poor sleep quality and habits are expected among older adults, which might diminish the benefits of sleep-mediated memory consolidation for language learning. Given that older adults tend to suffer from sleep disorders and impaired sleep-dependent memory consolidation in their daily lives, it is essential to develop effective interventions incorporating sleep hygiene and language learning programs. ASSESSMENT We examined the difference in sleep-mediated memory consolidation between Mandarin-speaking older adults and their younger counterparts in learning novel Cantonese words. Cantonese Novel Word Learning in Young Adults 46 Mandarin-speaking young adults aged between 19 and 33 were recruited to participate in the Cantonese novel word learning program. Following a language background survey, we found that none spoke Southern Chinese dialects, including Cantonese, or had resided in Hong Kong for more than one year. We also confirmed all participants had regular sleep patterns before the experiment. On Day 1, participants were asked to learn novel words adapted from Cantonese for a total training length of 6 blocks. They were subsequently assessed using “Post-test 1” to measure their learning outcomes between 8 p.m. and 10 p.m. Following a full-night sleep (12-hour interval) they returned to finish an identical “Post-test 2” between 9 a.m. and 10 a.m. on Day 2. We conducted a mixed-effect logistic regression model on the word-recall accuracy (binary variable: correct = 0, incorrect = 1) of Post-tests 1 (before sleep) and Post-test 2 (after sleep) to study whether they successfully consolidated novel words through sleep-dependent memory consolidation. Post-test (two levels: Post-test 1 and 2) was entered into the model as an independent variable. The results revealed that the accuracy of word recall among younger adults was significantly improved from Post-test 1 to Post-test 2 after sleep (p-value < .001, see Figure 1). This indicates that Mandarin-speaking younger adults successfully consolidated Cantonese novel words, and that sleep promoted their learning. Figure 1. Word-recall Accuracy Changes Before and After Full-Night Sleep (Younger adults) Cantonese Novel Word Learning in Older Adults To investigate the possibility of age-related decline in sleep-dependent memory consolidation, we recruited 60 Mandarin-speaking older adults aged between 55 and 78 from Nanjing, China, to participate in a similar program of novel word learning. None were found to speak Cantonese. All participants passed the screening with near-normal cognitive ability, which was assessed by the Montreal Cognitive Assessment (MoCA). Their hearing thresholds were measured by pure-tone audiometry. All of them maintained near-normal hearing abilities and self-reported to have regular sleep patterns. We split the participants into 2 groups where half received the same training as the younger adults (six blocks, forming a shorter training group), while the other half received a lengthened training (ten blocks, forming a longer training group). The words used in training were identical to those used for younger adults for both groups. They completed training and Post-test 1 between 7 p.m. and 9 p.m. on Day 1. After a full-night sleep, they returned and completed Post-test 2 between 7 a.m. and 9 a.m. on Day 2.
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