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Memory consolidation in sleep disorders
Get PDFIn recent years sleep-related memory consolidation has become a central topic in the sleep research field. Several studies have shown that in healthy individuals sleep promotes memory consolidation. Notwithstanding this, the consequences of sleep disorders on offline memory consolidation remain poorly investigated. Research studies indicate that patients with insomnia, obstructive sleep apnea, and narcolepsy often exhibit sleep-related impairment in the consolidation of declarative and procedural information. On the other hand, patients with parasomnias, such as sleep-walking, night terrors and rapid eye movement (REM) behavior disorder, do not present any memory impairment. These studies suggest that only sleep disorders characterized by increased post-learning arousal and disrupted sleep architecture seem to be associated with offline memory consolidation issues. Such impairments, arising already in childhood, may potentially affect the development and maintenance of an individual's cognitive abilities, reducing their quality of life and increasing the risk of accidents. However, promising findings suggest that successfully treating sleep symptoms can result in the restoration of memory functions and marked reduction of direct and indirect societal costs of sleep disorders
The Effects Of Sleep On Autonomic Regulation, Cardiovascular Activity, And Cognitive Processing
Get PDFSleep is a cyclical behaviour that occurs every day and we spend a significant portion of our life sleeping. While “why do we sleep” remains an unanswered question, we know that sleep is essential for life. Several aspects of our life are dependent on or strictly related to sleep, from molecular and hormonal levels to high-functional behaviours.
The main purpose of the present dissertation is to investigate through five experiments two of the most fundamental aspects of human life, cardiovascular regulation and cognitive function, in relation to different sleep situations such as healthy and pathological sleep (i.e. insomnia) as well as nocturnal and diurnal sleep. Specifically, the current thesis was aimed to shed further light on some debated aspects of the relationship between sleep and cardiovascular activity (Study 1 and 3) and cognitive abilities (Study 3 and 4) in young adults with insomnia. Moreover, the present dissertation aimed to investigate, to our knowledge for the first time, cardiac autonomic activity during daytime sleep (Study 2) and the effect of sleep on selective attention (Study 5).
During sleep, we observed a predominant control of the parasympathetic branch of the ANS and a reduction of sympathetic activity. Thus, during sleep the cardiovascular system “takes a break” and reduces its activity compared to wakefulness, when the sympathetic system is predominant. Interestingly, our results showed a similar cardiac autonomic pattern in diurnal sleep. Thus, it appears that it is sleep itself, rather than a specific moment of the day, that is responsible for this cardiovascular break and that daytime sleep can also act as a cardio-protective period. However, when sleep is disturbed, such as in insomnia, the autonomic balance becomes dysfunctional, with a continuously high sympathetic activity. This elevated cardiovascular activity in insomniacs occurs not only during sleep but also during daytime wakefulness. Indeed, we observed a dysfunctional cardiac autonomic profile during sleep and an elevated cardiovascular activity at rest and during the execution of cognitive tasks in young individuals with disturbed sleep. When this period is disturbed, such as in insomnia, the autonomic regulation becomes dysfunctional, leading to an elevated cardiovascular activity which expose individuals to possible long-term cardiovascular risk.
We also confirm the key role of sleep in cognitive functioning. In healthy individuals we observed a well-established “sleep effect”, i.e. the sleep-related enhancement of procedural memory. However, insomniacs did not show this effect. Also, in insomniacs we observed working memory impairments. Thus, it seems that a disturbed sleep can not only directly impact nighttime cognitive processing (i.e. the sleep-related memory consolidation), but can also affect daytime cognitive functions such as working memory. In addition, we documented the role of sleep in the improvement of attentional abilities, showing a relationship between light sleep and sleep spindles with the magnitude of improvement.Ognuno di noi trascorre una parte significativa della propria vita dormendo. Tuttavia, ad oggi la domanda “perché si dorme?” è ancora senza risposta. Nonostante ciò sappiamo che il sonno è un elemento fondamentale della nostra vita. Lo scopo principale della presente tesi è indagare il rapporto tra sonno e due aspetti vitali della vita umana, la regolazione cardiovascolare e il funzionamento cognitivo. In particolare, nella presente tesi sono stati studiati alcuni aspetti ancora poco chiari del rapporto tra sonno, attività cardiovascolare (Studio 1 e 3) e capacità cognitive (Studio 3 e 4) in giovani adulti con insonnia. Inoltre, nella presente dissertazione è stata investigata l'attività autonoma cardiaca durante il sonno diurno (Studio 2 ) e l' effetto del sonno sull’attenzione selettiva (Studio 5 ).
I nostri risultati mostrano come durante il sonno l’attività autonoma prevalente sia quella parasimpatica, mentre l'attività simpatica tenda a ridursi. I risultati sembrano inoltre indicare come durante il sonno il sistema cardiovascolare "si riposi”, riducendo la sua attività rispetto alla veglia quando è il sistema simpatico a predominare. I nostri risultati hanno anche mostrato come durante il sonno diurno il profilo dell’attività cardiaca autonoma fosse simile a quello notturno. Questi dati indicano come sia il sonno stesso, piuttosto che uno specifico momento della giornata, a facilitare questo “rilassamento” cardiovascolare suggerendo come anche il sonno diurno possa fungere come periodo cardio-protettivo. Tuttavia quando il sonno è disturbato, come nell’insonnia, il bilanciamento autonomo diventa disfunzionale, in quanto caratterizzato da una costante ed elevata attività simpatica. Negli insonni questa elevata attività cardiovascolare sembra essere presente anche durante la veglia diurna. Abbiamo infatti osservato negli insonni sia un profilo autonomo disfunzionale durante il sonno sia un’elevata attività cardiovascolare a riposo e durante l'esecuzione di compiti cognitivi. Quindi quando il sonno è disturbato, come nell’insonnia, la regolazione autonoma diventa disfunzionale portando ad una elevata attività cardiovascolare che espone le persone a possibile rischi cardiovascolari a lungo termine.
Abbiamo inoltre confermato l’importanza del sonno nel funzionamento cognitivo. Abbiamo infatti osservato, in individui sani, come il sonno faciliti il consolidamento e il miglioramento di informazioni procedurali. Tuttavia questo effetto non è stato osservato negli insonni. Inoltre negli insonni abbiamo osservato difficoltà anche a carico della memoria di lavoro. Questi risultati suggeriscono che un sonno disturbato non solo influenzi direttamente l’elaborazione cognitiva durante la notte, come il consolidamento sonno-dipendente delle informazioni, ma influisca anche su altre funzioni cognitive come la memoria di lavoro. Infine, abbiamo descritto il ruolo del sonno nel miglioramento delle capacità attentive, osservando una relazione tra sonno leggero, fusi del sonno e miglioramento attentivo
Stimulating the sleeping brain: Current approaches to modulating memory-related sleep physiology
Get PDFBackground: One of the most audacious proposals throughout the history of psychology was the potential ability to learn while we sleep. The idea penetrated culture via sci-fi movies and inspired the invention of devices that claimed to teach foreign languages, facts, and even quit smoking by simply listening to audiocassettes or other devices during sleep. However, the promises from this endeavor didn't stand up to experimental scrutiny, and the dream was shunned from the scientific community. Despite the historic evidence that the sleeping brain cannot learn new complex information (i.e., words, images, facts), a new wave of current interventions are demonstrating that sleep can be manipulated to strengthen recent memories. New method: Several recent approaches have been developed that play with the sleeping brain in order to modify ongoing memory processing. Here, we provide an overview of the available techniques to non-invasively modulate memory-related sleep physiology, including sensory, vestibular and electrical stimulation, as well as pharmacological approaches. Results: N/A. Comparison with existing methods: N/A. Conclusions: Although the results are encouraging, suggesting that in general the sleeping brain may be optimized for better memory performance, the road to bring these techniques in free-living conditions is paved with unanswered questions and technical challenges that need to be carefully addressed
How elderly people’s quality of life relates to their sleep quality and sleep-related beliefs
No full textObjective/Background: Quality of life (QoL) is a broad multidimensional construct, which can be influenced by several factors across the lifespan, including sleep quality. The aim of this study was to examine the association between QoL (and its specific domains), objective and self-reported sleep quality, and subjective sleep-related factors (i.e., dysfunctional beliefs and attitudes about sleep, and metacognitive beliefs about sleeping difficulties) in healthy elderly people. Participants: Fifty healthy older adults (mean age = 70.40 years, SD = 7.43) participated in the study. Methods: QoL was assessed using the World Health Organization’s Quality of Life Assessment, BREF version (WHOQOL-BREF). Self-reported sleep quality and efficiency were measured with the Pittsburgh Sleep Quality Index (PSQI) and sleep diary. Dysfunctional beliefs and attitudes about sleep (DBAS), and metacognitive beliefs about sleeping difficulties (MCQ-I) (subjective sleep related factors) were assessed with self-report questionnaires. Objective sleep quality and efficiency were measured using actigraphy over 7 days. Results: Regression analyses showed that self-reported sleep efficiency and dysfunctional beliefs and attitudes about sleep explained 24% of the variance in global QoL. Dysfunctional beliefs and attitudes about sleep were the only significant predictor of QoL in the environmental domain. Conclusions: Taken together, these findings underscore the influence of sleep-related factors, and particularly dysfunctional beliefs and attitudes about sleep, along with sleep efficiency, on the perception of QoL in healthy older adults. These factor
Shaping memory consolidation via targeted memory reactivation during sleep
Get PDFRecent studies have shown that the reactivation of specific memories during sleep can be modulated using external stimulation. Specifically, it has been reported that matching a sensory stimulus (e.g., odor or sound cue) with target information (e.g., pairs of words, pictures, and motor sequences) during wakefulness, and then presenting the cue alone during sleep, facilitates memory of the target information. Thus, presenting learned cues while asleep may reactivate related declarative, procedural, and emotional material, and facilitate the neurophysiological processes underpinning memory consolidation in humans. This paradigm, which has been named targeted memory reactivation, has been successfully used to improve visuospatial and verbal memories, strengthen motor skills, modify implicit social biases, and enhance fear extinction. However, these studies also show that results depend on the type of memory investigated, the task employed, the sensory cue used, and the specific sleep stage of stimulation. Here, we present a review of how memory consolidation may be shaped using noninvasive sensory stimulation during sleep
The Mechanisms of Space-Time Association: Comparing Motor and Perceptual Contributions in Time Reproduction
No full textThe spatial-temporal association indicates that time is represented spatially along a left-to-right line. It is unclear whether the spatial-temporal association is mainly related to a perceptual or a motor component. In addition, the spatial-temporal association is not consistently found using a time reproduction task. Our rationale for this finding is that, classically, a non-lateralized button for performing the task has been used. Using two lateralized response buttons, the aim of the study was to find a spatial-temporal association in a time reproduction task. To account for the perceptual component, reference and target stimuli were presented in different spaces through four experiments. In all experiments, a Spatial-Temporal Association of Response Codes (STEARC) effect was found and this effect was not modulated by the spatial position of both reference and target stimuli. The results suggested that the spatial-temporal association was mainly derived from the spatial information provided by response buttons, reflecting a motor but not visuospatial influence
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