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Sleep significantly alters throughout the lifespan, as a consequence of changes in brain maturation, circadian system changes, and environmental influences. Significant associations have been established between suboptimal sleep duration and efficacy and anxiety and depression symptomatology (Qiu & Morales-Munoz, 2022; O'Callaghan et al., 2021; Blake, Trinder, & Allen, 2020). However, the mechanisms which underlie the relationship between sleep and mental health are poorly understood. This understanding is paramount as it allows for the development of interventions to improve sleep quality and quantity and reduce the risk of mental ill health. A possible neurocognitive mechanism that may link sleep and mental health could be executive functioning. Specifically, poor sleep reduces executive control which in turn compounds mental health (Harrington & Cairney, 2021), suggesting that executive functioning thus plays a mediatory role. Suboptimal sleep has been previously associated with executive function deficits (Dai et al., 2020; Skurvydas et al., 2020; Kusztor et al., 2019). Additionally, poorer executive control has been associated with emotion regulation strategies (Dryman & Heimberg, 2018; Snyder, 2013; Malooly et al., 2013) which have been reported to be suboptimal in individuals with mood disorders (Engen & Anderson, 2018). Previous research has explored the relation amongst sleep, cognitive control and depressive symptoms in young adults, indicating that sleep disruptions contribute to depressive symptoms via executive control (Vanderlind et al., 2014). Previous pathway analysis has demonstrated a significant model finding that both subjective and objective measures of sleep difficulties significantly predicted less cognitive control over negative stimuli, which in turn predicted an increase in depressive symptomatology in young adults (Vanderlind et al., 2014). This study aims to examine the relationship between sleep and mental health as mediated by executive control in young adults aged between 18 and 24 years old.

Previous research has shown that encountering a word in a sentential context that biases its interpretation towards a subordinate meaning aspect leads to that meaning subsequently being more easily accessible (e.g., Curtis et al., 2022). This finding, referred to as word-meaning priming, illustrates the malleability of word meanings, and research within this paradigm has shed some light on the time course and constraints on this type of lexical-semantic updating (e.g., Gaskell et al., 2019; Gilbert et al., 2021; Rodd et al., 2013, 2016). However, the exact mechanism underpinning this flexibility remains contested. One explanation, called the episodic context account (Gaskell et al., 2019; Curtis et al., 2022; Mak et al., 2022), suggests that word-meaning priming is supported by general episodic memory processes, whereby word meanings are initially bound to the context they are encountered in by the hippocampus. Crucially, if word-meaning priming is supported by episodic memory processes, then the strength of word-meaning priming effects should be affected by factors that have previously been shown to affect learning in (other) episodic memory paradigms (e.g., Greve et al., 2018; Quent et al., 2022). One important finding in this regard (replicated across several different paradigms, e.g., van Kesteren et al., 2013; Greve et al., 2018; Quent et al., 2022) is that the expectedness of a stimulus influences the extent to which participants are able to remember that input (see Quent et al., 2021 for a recent review). The main aim of the present study is to test whether the expectedness of a stimulus has an influence on the strength of the word-meaning priming effect, as would be predicted if word-meaning priming is supported by general episodic memory processes (see the ‘study design’ section for details of the experimental design). In the present experiment, participants will be exposed to sentences containing a target word whose interpretation is biased towards a specific aspect of its meaning by the preceding sentential context (i.e., the word-meaning priming manipulation). As stated above, if word-meaning priming is affected by similar factors as have been shown to affect memory in (other) episodic memory paradigms, then the strength of the word-meaning priming effect should be affected by the relative expectedness of the target word. Therefore, the central question is whether expectedness has an impact on word-meaning priming. A subsidiary aim is to test the prediction derived from the models of episodic memory cited above that memory for incidental aspects of the experiment will be better if these are processed in close temporal proximity to unexpected input (compared to expected or neutral input). Cued recall and 2AFC tests probing memory for incidental aspects of the main experiment will address this hypothesis (see ‘incidental memory test’ in the ‘study design’ section below).

This study will examine the effect of sleep deprivation on state anxiety using virtual reality (VR), psychophysiology, polysomnography and self-report measures. State anxiety can be defined as a transitory emotional state consisting of feelings of apprehension, nervousness, and physiological sequelae such as an increased heart rate or respiration (Spielberger, 1979). Although previous research has shown that state anxiety is amplified after sleep deprivation (Ben Simon et al., 2020; Pires et al., 2016), this research has only assessed anxiety responses at specific moments in time. Consequently, we know very little about how insufficient sleep affects the evolution of anxiety during unfolding ambiguous threats. In addition, it has been shown that specific properties of sleep (specifically, the amount of EEG slow wave activity [SWA, 0.5-4 Hz]) support the overnight reduction of state anxiety (Ben Simon et al., 2020). How SWA influences anxiety responses to unfolding ambiguous threats, however, remains unknown. In order to address these gaps in understanding, we will investigate the following research questions: 1. Does sleep deprivation amplify the evolution of state anxiety during an unfolding ambiguous threat? 2. Does SWA support the overnight reduction of state anxiety during an unfolding ambiguous threat?

A ‘sleep debt’ is widely reported among adolescents. Addressing this is of societal importance given that sleep deprivation has been linked to a range of cognitive and affective disturbances. Initial evidence suggests that modest gains in total sleep time over a week or less can improve attention and mood in adolescents; however, extant studies have methodological caveats and findings have been inconsistent. The present proof-of-concept study tests a protocol for extending sleep duration in teens. We also explored whether this has benefits for daytime sleepiness, mood, attention and word learning. Thirty-nine 13-15-year-olds who were sleeping less than the recommended 9 hours per night completed one week of baseline sleep monitoring before being randomly allocated to a control (business as usual) group or a four-night sleep extension group where individuals’ bedtimes were gradually brought forward. The extension protocol successfully increased total sleep time by ~50 minutes on average but did not alter sleep efficiency or time spent in different sleep stages. Decreases in subjective sleepiness were associated with increases in sleep duration. There were no observed benefits for mood or cognitive abilities. These data suggest that adolescent sleep can be modified over a short time span, and call for further research into how to optimize sleep to bolster cognitive and affective performance in adolescence.

PhD project investigating the effect of sleep deprivation on consolidation and encoding.

Background: In their seminal study, Wilhelm et al. (2011) found that the memory benefits of sleep were enhanced when participants expected a test, suggesting that sleep selectively strengthens memories expected to be of future relevance. We failed to replicate this finding in recent work, with our data showing that memories were strengthened over sleep (vs wake) irrespective of whether participants expected a test or not (see Experiment 1). A potential explanation of this failed replication is that baseline performance levels were too high to allow a benefit of test-expectancy to emerge after sleep. To address this possibility in the current study, we will repeat Experiment 1, but increase the difficulty of our memory task to reduce baseline performance. Procedure: Learning takes place in the morning (Wake group) or evening (Sleep group). Participants encode 100 related word pairs (e.g. horizon-sun), with each pair appearing for 5 s (200 ms inter-stimulus interval). A cued recall task is used to assess baseline memory performance immediately after learning. On each trial, the first word of the pair (e.g. horizon) is presented and participants are asked to type the associated target word (e.g. sun) within 10 s. Feedback on the correct pairing is displayed irrespective of the participant’s response. The cued recall task is repeated if participants do not reach a performance criterion of 40% correct. Participants are excluded if they do not meet this criterion after two testing rounds. After the baseline test, participants are either informed that they will be re-tested in the next session (Expected condition) or are told that they will perform a different set of tasks (Not Expected condition). Twelve hours later, participants return to complete a final round of cued recall without feedback.

Sleep supports memory consolidation (Gais et al., 2006; Born & Wilhelm, 2012; Klinzing et al., 2019) and next-day learning (Yoo et al., 2007; Cousins et al., 2018; Mander et al., 2001; Ong et al., 2020). The Active Systems Consolidation (ASC) framework posits that memories are gradually transferred from hippocampus to neocortex during sleep for long-term storage. This overnight memory transfer is thought to pave the way for new learning in hippocampus, but evidence directly supporting this hypothesis is lacking. In recent work (https://osf.io/pjwrn/), we tested the hypothesis that sleep-associated consolidation would predict next-day learning. Participants were trained on a visuospatial task in the evening before a night of sleep or sleep deprivation and were tested again the following morning. Importantly, participants also learned novel paired associates the morning after sleep or sleep deprivation, and were tested on these pairs two days later (allowing for recovery sleep). Retrieval performance on the visuospatial memory and paired-associates tests thus provided independent metrics of overnight consolidation and next-day learning, respectively. Although sleep (vs sleep deprivation) benefited performance on both measures, there was no correlation between them, suggesting that sleep-associated consolidation may not predict next-day learning. A parsimonious explanation of this null finding is that we were unable to capture a relationship between sleep-associated consolidation and next-day learning because these processes were indexed by two distinct tasks. In the current study, we will address this possibility by using a word pair task to assess both consolidation and encoding. Whereas our previous work was carried out in the lab, the current study will be run entirely online due to ongoing limitations on social contact resulting from the COVID-19 pandemic. Procedure Participants will complete two experimental sessions. For the wake group, the first session will take place in the morning and the second session in the evening. For the sleep group, the first session will take place in the evening and the second session in the morning. At session one, participants will learn 60 semantically-related word-pairs (A-B) and then complete an immediate cued recall test for 30 of the pairings (A-Bimm). At session two, participants will first be tested on the remaining 30 A-B word-pairs (A-Bdel). Following this, they will learn a new set of 30 semantically-related word-pairs (C-D) and complete an immediate cued recall test for all 30 C-D word-pairs. During the learning of the word-pair tasks, participants will view each word-pair for 4 seconds (ISI = 1s). Attention check trials will be randomly intermixed among word pair trials. During attention check trials, a pair of 4-digit numbers will appear on the screen. Participants must hit the space bar within 5 seconds to pass the attention check. There will be 12 attention check trials in the first learning task (session one; 60 pairs), and 6 attention check trials in the second learning task (session two; 30 pairs). During recall of the word-pair tasks, participants will be presented with the first word of each pair (cue word), and will have 15 seconds to type the corresponding word of the pair (target word). If participants are unable to recall the correct target word, they must type the cue word. For example, if the word pair was table─chair, and the participant was unable to remember the target word chair, they would type the cue word table. A word-pair decay index will be calculated as the difference in A-B cued recall performance (percent correct) between session one and session two. A word-pair learning index will be calculated as C-D cued recall performance (percent correct) at session two. To test whether any benefit of sleep-associated consolidation on next-day learning is specific to word-pair learning, participants will also complete a visuospatial task in the first session (training and test) and second session (test only). The task is an online version of the visuospatial task from our previous study. From the visuospatial task, we will first compute the distance between the target location and test location which will render an error score (i.e. distance from the target location). The visuospatial memory decay index will then be calculated as the difference in error scores between session one and session two.

Background Memories fade over time, but reengaging with learned materials can help to reduce memory decay. Memory rehearsal can be carried out via relearning or retrieval practice. Typically, relearning benefits retention in the short-term (Bai, Bridger, Zimmer, & Mecklinger, 2015; Kornell, Bjork, & Garcia, 2011; Roediger & Karpicke, 2006), whereas longer-term advantages have been observed following retrieval practice (Carpenter, Pashler, Wixted, & Vul, 2008; Roediger & Karpicke, 2006). Interestingly, overnight sleep, as compared to daytime wakefulness, facilitates the consolidation of relearned but not retested memories (Bäuml, Holterman & Abel, 2014; Antony & Paller, 2018). It has been suggested that retrieval practice prompts a rapid consolidation of new information, potentially via similar mechanisms to those underpinning the benefits of sleep for memory (Antony, Ferreira, Norman, & Wimber, 2017). We will test this hypothesis using a source memory paradigm, assessing the effects of relearning and retrieval practice on sleep- and wake-based consolidation. Previous work has suggested that memories compatible with pre-existing cognitive schemata benefit from sleep to a greater extent than those that are schematically-incongruent (Durrant, Cairney, McDermott, & Lewis, 2015; Lewis & Durrant, 2011). Moreover, synaptic downscaling during sleep might diminish weak and incongruent representations below a threshold for successful retrieval (Tononi & Cirelli, 2003, 2006). Whether the overlap between new information and existing knowledge influences interactions between online rehearsal and sleep-associated memory processing, however, is unknown. We will examine this question by gauging the plausibility of newly formed source memories, enabling us to determine the fate of schematically-congruent and incongruent representations. Procedure Learning will take place in the morning (wake group) or evening (sleep group). On each learning trial, participants will be presented with a noun (e.g. ‘elephant’) and a colour (e.g. red). Participants will be asked to imagine the referent of the noun in the given colour and indicate whether it is a plausible or implausible combination (e.g. a red elephant is implausible). Baseline memory performance will be assessed immediately after learning. The nouns presented at learning will be intermixed with foils. On each test trial, participants will be presented with a noun and asked to indicate if it is ‘Old’ or ‘New’. For ‘Old’ responses, participants will also be asked to identify the colour associated with the noun (red, yellow, green or blue). Where the colour is correctly identified, the noun-colour pairings will be randomly and equally divided into three conditions (Relearning, Retrieval Practice and No Rehearsal). After a short break, participants will complete another round of learning for noun-colour pairings in the Relearning condition and another round of testing for noun-colour pairings in the Retrieval Practice condition. Noun-colour pairings in the No Rehearsal condition will not undergo any rehearsal. Participants will return for follow-up sessions at 12 hours and 24 hours after learning. In each follow-up session, they will repeat the baseline memory test.

Sleep supports memory consolidation (Rasch & Born, 2013) and helps prepare the brain for new learning (e.g. Cousins, Sasmita, & Chee, 2018; Harrison & Horne, 2000; Mander, Santhanam, Saletin, & Walker, 2011; Ong, Lau, Lee, van Rijn, & Chee, 2020; Yoo, Hu, Gujar, Jolesz, & Walker, 2007). It remains to be seen, however, whether these two processes are related. In this study, we will investigate whether sleep-associated memory consolidation affects the capacity to learn new information the following day.

In this study we tested the hypothesis that sleep deprivation impairs the capacity to keep unwanted thoughts out of mind. After a night of either sleep or total sleep deprivation, participants attempted to suppress intrusions of emotionally negative and neutral scenes when confronted with reminders. The sleep-deprived group experienced significantly more intrusions (unsuccessful suppressions) than the sleep group. For rested participants, suppression reduced behavioural and psychophysiological indices of negative affect for emotionally negative scenes, but had no such salutary effect for sleep-deprived participants. Our data point to an important role of sleep disturbance in maintaining and exacerbating psychiatric conditions characterised by persistent, unwanted thoughts.

The study will examine how changes in background context influences memory for objects that are semantically congruent or incongruent with the background context across a period of 1-week.

Stage 1 IPA at PCI RR

Memory reactivation during sleep can shape new memories into a long-term form. Reactivation of memories can be induced via the delivery of auditory cues during sleep. Although this targeted memory reactivation (TMR) approach can strengthen newly acquired memories, research has tended to focus on single associative memories. It is less clear how TMR affects retention for overlapping associative memories. This is critical, given that repeated retrieval of overlapping associations during wake can lead to forgetting; a phenomenon known as retrieval-induced forgetting (RIF). We asked if a similar pattern of forgetting occurs when TMR is used to cue reactivation of overlapping pair-wise associations during sleep. Participants learnt overlapping pairs; learnt separately, interleaved with other unrelated pairs. During sleep, we cued a subset of overlapping pairs using TMR. While TMR increased retention for the first encoded pairs, memory decreased for the second encoded pairs. This pattern of retention was only present for pairs not tested prior to sleep. The results suggest that TMR can lead to forgetting; an effect similar to RIF during wake. However, this effect did not extend to memories that had been strengthened via retrieval prior to sleep. We therefore provide evidence for a reactivation-induced forgetting effect during sleep.