Memory consolidation in typical and atypical development

Sleep is known to affect the consolidation process that takes fragile memories and makes them robust. Components of sleep such as "slow oscillations" influence this consolidation process. However, little is known about how children's sleep may influence consolidation. This is important: children's sleep has more of the components that are crucial for consolidation of memory, and may show more substantial effects. Given that children encounter new information at a dramatic rate, it is important to understand what factors influence consolidation to ensure that learning is optimal. Furthermore, sleep difficulties are common in childhood, particularly in neurodevelopmental disorders characterised by language learning impairments (e.g., autism spectrum disorder; ASD), but little progress has been made in examining whether learning and sleep difficulties are related in these groups. Comparisons across ages, as well as between typical and atypical groups of the same age, offer an opportunity to test theories of consolidation in terms of whether they can explain the substantial variability across and within development.

Our plans provide a comprehensive evaluation of the influence of sleep on consolidation of memory in development. Strand 1 focuses on typical development, using children aged 10-12 (when slow-oscillation activity peaks), as well as adults, and in some cases younger children. Strand 2 focuses on atypical development, comprising the first systematic evaluation of whether atypical sleep relates to language learning difficulties in children with ASD with varying language phenotypes and in children with language impairment (LI) without ASD. This enables us to separate learning mechanisms associated with ASD from those attributable to language impairment.

Our experiments involve learning of new materials, followed by a delay. For sleep conditions, participants' brain activity is recorded at home. Later tests determine the strength and nature of the new memory. For example, one study addresses whether sleep facilitates stabilisation of new memories, and looks at the optimal delay between learning and sleep (which may be particularly pertinent for children). Another examines the influence of prior knowledge on consolidation during sleep. Adults and children differ in terms of the prior knowledge that they bring to a learning situation and it is possible that this can mask the stronger consolidation ability of children. Furthermore, children with language impairments have impoverished vocabularies which may lead to a 'Matthew Effect' (i.e., the rich get richer and the poor get poorer) in the consolidation of new words; our studies will test this hypothesis directly.

Many studies focus on the role of sleep in language learning. We track the timecourse of learning spoken words and their meanings, and the extent to which this new information is strengthened over time, integrated with existing knowledge, and generalised to new exemplars. Such studies permit a thorough examination of whether language learning difficulties are associated with differences in sleep architecture in ASD and LI. We will exploit data collected from the same children over a 2-year period to examine whether sleep variables predict vocabulary outcomes over a longer period.

Finally, in a cross-cutting study we examine the generality of any effects of sleep across both typical and atypical development by examining the influence of sleep in a rather different type of memory that is nonetheless dependent on consolidation: spatial location.

We aim to create a comprehensive theory of typical and atypical consolidation and forgetting across wake and sleep, and advance theories of typical language acquisition and language heterogeneity in ASD and LI. The theoretical applications of the planned research have the potential to improve our practical understanding of how to make memories stick in children and adults, and ultimately improve outcomes.

This research is fundamental science and its primary impact is scientific. However, we envisage societal impact in several areas, with the time-scale medium to long-term.

Educational sector - The research will enhance understanding of the conditions that lead to initially fragile memories becoming more robust over time. This should have practical benefits for all ages in terms of defining optimal learning sessions (e.g., for 1st and 2nd language learning or university education). Given the focus on children there should be particular interest in the educational ramifications. Previous research on pedagogical methods for enhancing learning in school has focused on the factors that benefit encoding rather than retention. We address questions such as: "How do we learn and retain new information?", "How does sleep influence the ability to retain information?","What is the role of sleep in language learning?", "Is there an optimal time span between encoding and sleep for consolidation?", and "How does knowledge advantage sleep-dependent consolidation?". Addressing such questions may facilitate better educational practice (e.g., how best to structure the day for the most effective retention), realistic expectations about the effects of learning, and when best to assess retention.

Clinical sector - The research will directly contribute to understanding of the link between sleep and language development in ASD and LI. Current estimates of the annual cost of supporting adults with ASD in the UK exceed £34 billion. Language outcomes are one of strongest predictors of academic, social and emotional outcomes. If we can better understand the contributing factors associated with language problems then we can better support individuals with such problems (e.g., by informing teachers, carers, therapists), and potentially pursue new treatments or intervention in the longer term. The findings would be of relevance to charities associated with ASD (e.g., NAS, Autistica) and LI (e.g., Afasic, RALLI, of which Norbury is a founding member), who may wish to raise awareness and support. More broadly, the findings may be relevant to the understanding of the implications of a range of disorders involving sleep problems (e.g., dyslexia, ADHD, Landau-Kleffner syndrome, sleep apnoea, insomnia).

Wider public - Our research has lesser implications for the general public by highlighting the value of sleep for cognition and learning. This has potential benefits in terms of discouraging damaging practices amongst children such as minimising sleep, use of media devices before bed, or "cramming" before exams and is of particular relevance to shift workers.

Staff on the project - The postdoctoral researcher and research assistants will gain valuable experience in the full range of academic tasks required for a career in academic research. Bursary students and casual student workers will also gain experience in research and the lab environment, which is becoming almost a prerequisite for PhD funding. The opportunities and experiences gained by the staff will also be applicable to an array of non-academic employment sectors (e.g., public liaison, communication and social awareness; problem solving; creativity and innovation; application of IT and numeracy).

The following activities will work to maximise impact: Articles and presentations to target practitioner audiences (e.g., Children's Sleep Charity, National Autistic Society, RALLI; Association for Science Education) and public audiences (e.g., British Science Festival); workshops and research symposia; communication with established contacts in educational and clinical settings (e.g., educational/clinical psychologists, child psychiatrists, special educational needs coordinators, teachers and head teachers) and advice from colleagues at the Institute for Effective Education in York; press releases, publications on our website, via Twitter and through our annual research lab newsletters.