The underpinnings of linguistic optimisation in comprehension

It is now well-established that sleep, plasticity, and memory consolidation mechanisms are crucial for successful adult communication, particularly when a language involves a clearly novel item such as a new word. Recently, an intriguing addition to this literature opened up a new potential role for memory consolidation, this time moving beyond simple novelty. A recent study from our group suggested that sleep and memory consolidation may also operate to support everyday language comprehension even in the absence of new linguistic units. Here we comprehensively address whether and how these memory systems underpin comprehension. Three possible roles for sleep and memory consolidation in comprehension are considered here:

1) They help us to refine the mental representations of words to ensure optimal future comprehension.
2) They help us to track the linguistic events that are referred to during conversation, facilitating effective dialogue over a range of time-spans.
3) They help us to identify and maintain speaker-specific preferences in the way language is used.

All of these roles can be thought of as ways of optimising our ability to use language in conversation, or in reading and writing. Indeed any or all of these roles may turn out to be correct, and an exciting possibility is that at some level there might be a framework for unifying these disparate aspects of language comprehension based on the same underlying memory processes. The current proposal develops and tests these accounts, allowing us to understand for the first time the extent to which sleep and memory consolidation underpin and maintain our day-to-day ability to use language.

The proposed research is intended to answer fundamental questions about the way in which we comprehend and retain linguistic encounters. Language is at the heart of human interaction and is of primary importance to society. Therefore we can see widespread impact in the medium to long term in the following areas.

Educational sector: Our research has direct implications for educational practices across the sector. At a basic level, we hope to answer questions related to the time-course of retention of linguistic information (e.g., instructions from a teacher or a passage from a textbook). We hope that the research will inform on how best to organise teaching to acquire and build upon new knowledge at differing levels of representation. This would be relevant to educational practitioners (e.g., teachers, instructors) and policy-makers. For example, the study that provided the springboard for the current proposal showed that linguistic experience in the evening was better retained after 24 hours than the same experience in the morning. The implication is that time awake can lead to forgetting prior to an opportunity for consolidation. This feeds into the debate relating to school start times for adolescents, although implications may be wider (e.g., university curricula). The research may also guide educators' expectations in terms of retention over different periods of time, and in varying degrees of abstraction. More generally, our research addresses questions such as: "What makes some kinds of learning difficult?", "Does sleep lead to more generalisable knowledge?", and "What makes memories stick?" Better answers to these questions may facilitate both better educational practices in teaching and learning, and also more realistic expectations about the effects of new learning (e.g., a better understanding of what the immediate and delayed effects of learning are, and an understanding of the involvement of time and sleep in consolidation of new information).

Clinical sector: our research has relevance for learning and consolidation of knowledge in patient groups with disorders such as Parkinson's and Huntington's disease, given the complementary nature of the memory disorders in these groups. Little is known about the impact of sleep on learning and consolidation for these groups. Thus there is a possibility that vital delayed effects of learning (post-sleep) have been missed and can be exploited in more applied research. More generally, the research should be relevant to understanding of failures to learn in amnesia and the changes in learning and retention as people age and their sleep patterns change. A separate clinical area for which the research is of potential relevance involves sleep disordered groups, ranging from specific sleep disorders such as Landau-Kleffner syndrome to other disorders with associated sleep problems (e.g., autism) and widespread "low-level" sleep disorders such as sleep apnoea and insomnia. As above, part of the benefit of our research may be in terms of informing carers, clinicians and therapists in terms of what can realistically be expected in terms of retention of linguistic material over time.

Employment: here, as in education, the research may be valuable in terms of optimising the relationship between the sleep and language comprehension to deliver effective communication and greater productivity in the workplace. This message may be particularly useful in sectors where shift work is common, or where effective communication is particularly crucial.

Wider public: our research may have a broader impact on the general public by highlighting the importance of sleep for cognitive functioning and learning. This has potential benefits in terms of discouraging potentially damaging practices such as minimising sleep duration or all-night "cramming" sessions.

We view the potential impact of the research as relevant to two ESRC strategic priority areas: mental health and productivity.