Impaired procedural memory in narcolepsy type 1

Can sleep affect destination memory? A prospective narrative review

The destination memory is the ability of individuals to remember to whom the information has been delivered. The memory system is an essential and critical piece of social communication and human social cognition. Previously, research has been done on the relationship between source memory and sleep which are critical and fundamental processes influencing our daily lives. However, this present prospective narrative review sheds light on the idea of beginning new research to understand the relationship between destination memory and sleep. Although no such literature exists that can explain this relationship, this review will try to understand prospective future directions by synthesizing available literature on sleep and the source memory. The present narrative review provides an overview of research executed in the fields of source memory, destination memory, and sleep. Destination memory and source memory are the opposite sides of the same coin. They are a part of the episodic memory system. Research suggests that they share similarities, namely their contextual nature, involvement of the pre-frontal cortex (PFC), and role of the medial temporal lobe (MTL). Studies on the effect of sleep on source memory have indicated that it plays a role in consolidation. This consolidation involves binding the item to its context. Due to the shared characteristics of source and destination memory, it can be suggested that sleep may play a role in influencing destination memory. Understanding this relationship will have implications for enhancing social memory/communication efficacy through sleep hygiene.

The association between sleep disturbance and nightmares: Temporal dynamics of nightmare occurrence and sleep architecture in the home

We collected measures of sleep architecture and nightmares from participants (N = 61) wearing the DREEM 3 headband across 2 weeks of data collection to test the hypothesis that there are bidirectional links between insomnia (measured as sleep disturbance) and nightmare events. Nightmares were predicted by increased sleep disturbance the night before the nightmare, but not on the same night or 2 nights before. We also found that nightmare occurrences did not predict increased sleep disturbance on the same night or the following 2 nights, rather nightmares predicted increased sleep disturbance at the between-subjects level only. We suggest that nightmares are associated with an N3 sleep rebound on the night of the nightmare following a night of sleep disturbance.

Impaired cognition in narcolepsy: clinical and neurobiological perspectives

In addition to well-known symptoms such as sleepiness and cataplexy, many people with narcolepsy have impaired cognition, reporting inattention, poor memory, and other concerns. Unfortunately, research on cognition in narcolepsy has been limited. Strong evidence demonstrates difficulties with sustained attention, but evidence for executive dysfunction and impaired memory is mixed. Animal research provides some insights into how loss of the orexin neurons in narcolepsy type 1 may give rise to impaired cognition via dysfunction of the prefrontal cortex, and cholinergic and monoaminergic systems. This paper reviews some of these clinical and preclinical findings, provides a neurobiological framework to understand these deficits, and highlights some of the many key unanswered questions.

Effects of morning and evening physical exercise on subjective and objective sleep quality: an ecological study

To optimise the relationship between exercise and sleep quality, the intensity of exercise and its proximity to sleep are key factors to manage. Although low-to-moderate exercises promote sleep quality, late-evening vigorous exercise instead of morning should still be avoided. It potentially impacts the objective and subjective markers of sleep quality. In the present study, we investigated the effects of vigorous morning and evening exercise on objective and subjective sleep features in an ecological context. A total of 13 recreational runners (mean [SD] age 27.7 [7.2] years, four females) performed a 45-60 min run (70% maximal aerobic velocity) either in the MORNING (30 min to 2 h after waking-up) or in the EVENING (2 h to 30 min before sleep). The two exercise conditions were separated by a REST day. After each condition, sleep was objectively assessed using an electroencephalographic headband and subjectively using the Spiegel Sleep Inventory. Compared with REST, both MORNING and EVENING exercise increased the time spent in non-rapid eye movement (NREM, +24.9 min and +22.7 min; p = 0.01, η2  = 0.11, respectively). Longer NREM duration was mainly due to sleep stage 2 extension after both MORNING (+20.8 min) and EVENING (+22.8 min) exercise relative to REST (p = 0.02, η2  = 0.12). No other effect of exercise on either objective or subjective sleep could be observed. Exercise, independently of the time at which it takes place, leads to extended NREM sleep without other effects on sleep quality. Considering the crucial role of exercise in achieving good health, sleep hygiene guidelines should be updated to promote exercise at any time of the day.

Sleep Stage Transitions and Sleep-Dependent Memory Consolidation in Children with Narcolepsy-Cataplexy

Electroencephalographic sleep stage transitions and altered first REM sleep period transitions have been identified as biomarkers of type 1 narcolepsy in adults, but not in children. Studies on memory complaints in narcolepsy have not yet investigated sleep-dependent memory consolidation. We aimed to explore stage transitions; more specifically altered REM sleep transition and its relationship with sleep-dependent memory consolidation in children with narcolepsy. Twenty-one children with narcolepsy-cataplexy and twenty-three healthy control children completed overnight polysomnography and sleep-dependent memory consolidation tests. Overnight transition rates (number of transitions per hour), global relative transition frequencies (number of transitions between a stage and all other stages/total number of transitions × 100), overnight transitions to REM sleep (transition from a given stage to REM/total REM transitions × 100), and altered first REM sleep period transitions (transitions from wake or N1 to the first REM period) were computed. Narcoleptic children had a significantly higher overnight transition rate with a higher global relative transition frequencies to wake. A lower sleep-dependent memory consolidation score found in children with narcolepsy was associated with a higher overnight transition frequency. As observed in narcoleptic adults, 90.48% of narcoleptic children exhibited an altered first REM sleep transition. As in adults, the altered sleep stage transition is also present in children with narcolepsy-cataplexy, and a higher transition rate could have an impact on sleep-dependent memory consolidation. These potential biomarkers could help diagnose type 1 narcolepsy in children more quickly; however, further studies with larger cohorts, including of those with type 2 narcolepsy and hypersomnia, are needed.