Publications by authors named "Hong-Viet V Ngo"

Insomnia and nightmares are present in up to 45 % of individuals with borderline personality disorder (BPD) and can contribute to challenges with emotion regulation, low sleep quality, dream anxiety, increased arousal and self-control. Despite their prevalence, nightmares are usually not addressed in classical BPD treatment. Imagery rehearsal therapy (IRT) is considered first in line treatment for nightmares, however, there are no studies to date that investigate its effects in individuals with BPD.

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Insomnia is a prevalent and disabling condition whose treatment is not always effective. This pilot study explores the feasibility and effects of closed-loop auditory stimulation (CLAS) as a potential non-invasive intervention to improve sleep, its subjective quality, and memory consolidation in patients with insomnia. A total of 27 patients with chronic insomnia underwent a crossover, sham-controlled study with 2 nights of either CLAS or sham stimulation.

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Nightmares are common among the general population and psychiatric patients and have been associated with signs of nocturnal arousal such as increased heart rate or increased high-frequency electroencephalographic (EEG) activity. However, it is still unclear, whether these characteristics are more of a trait occurring in people with frequent nightmares or rather indicators of the nightmare state. We compared participants with frequent nightmares (NM group; n = 30) and healthy controls (controls; n = 27) who spent 4 nights in the sleep laboratory over the course of 8 weeks.

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Sleep is essential for our physical and mental well-being. During sleep, despite the paucity of overt behavior, our brain remains active and exhibits a wide range of coupled brain oscillations. In particular slow oscillations are characteristic for sleep, however whether they are directly involved in the functions of sleep, or are mere epiphenomena, is not yet fully understood.

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Circadian rhythms are imprinted in all organisms and influence virtually all aspects of physiology and behavior in adaptation to the 24-h day-night cycle. This recognition of a circadian timekeeping system permeating essentially all healthy functioning of body and mind quickly leads to the realization that, in turn, human ailments should be probed for the degree to which they are rooted in or marked by disruptions and dysregulations of circadian clock functions in the human body. In this review, we will focus on psychosis as a key mental illness and foremost one of its cardinal symptoms: auditory hallucinations.

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Recent advancements in real-time brain stimulation in the sleep field have led to many exciting findings. However, they have also opened up terminological ambiguities about what constitutes "open-loop", "closed-loop", and "real-time" designs. Here, we address core theoretical aspects of these terms in the hopes of strengthening future research on this topic.

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Sleep constitutes a privileged state for new memories to reactivate and consolidate. Previous work has demonstrated that consolidation can be bolstered experimentally either via delivery of reminder cues (targeted memory reactivation [TMR]) or via noninvasive brain stimulation geared toward enhancing endogenous sleep rhythms. Here, we combined both approaches, controlling the timing of TMR cues with respect to ongoing slow-oscillation (SO) phases.

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Real-time brain stimulation is a powerful technique that continues to gain importance in the field of sleep and cognition. In this special issue, we collected 14 articles about real-time stimulation during sleep, including one review, 12 research articles and one letter covering both human and rodent research from various fields. We hope this special issue sparks greater interest and inspires fellow sleep researchers and clinicians to develop new ideas in the exciting topic of real-time stimulation.

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Several epilepsies are characterized by interictal spikes in the electroencephalogram occurring preferentially during sleep. We present a closed-loop auditory stimulation protocol with potential for treating sleep epilepsies. We describe the pre-sleep preparations, sleep recordings, the auditory stimulation, in which tones are triggered upon spike detection, and post-sleep procedures.

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Sleep-dependent memory consolidation is disturbed in patients with schizophrenia, who furthermore show reductions in sleep spindles and probably also in delta power during sleep. The memory dysfunction in these patients is one of the strongest markers for worse long-term functional outcome. However, therapeutic interventions to normalise memory functions, e.

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The beneficial effects of sleep for memory consolidation are assumed to rely on the reactivation of memories in conjunction with the coordinated interplay of sleep rhythms like slow oscillations and spindles. Specifically, slow oscillations are assumed to provide the temporal frame for spindles to occur in the slow oscillations up-states, enabling a redistribution of reactivated information within hippocampal-neocortical networks for long-term storage. Memory reactivation can also be triggered externally by presenting learning-associated cues (like odours or sounds) during sleep, but it is presently unclear whether there is an optimal time-window for the presentation of such cues in relation to the phase of the slow oscillations.

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Benign epilepsy with centrotemporal spikes (BECTS) is a common form of childhood epilepsy linked to diverse cognitive abnormalities. The electroencephalogram of patients shows focal interictal epileptic spikes, particularly during non-rapid eye movement (NonREM) sleep. Spike formation involves thalamocortical networks, which also contribute to the generation of sleep slow oscillations (SOs) and spindles.

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Auditory closed-loop stimulation has gained traction in recent years as a means of enhancing slow oscillatory activity and, consequently, sleep-associated memory consolidation. Previous studies on this topic have primarily focused on the consolidation of semantically-congruent associations. In this study, we investigated the effect of auditory closed-loop stimulation on the overnight retention of semantically-incongruent associations.

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Article Synopsis
  • Amyloid-β is a waste product in the brain associated with cognitive decline and Alzheimer's disease.
  • A recent long-term study shows that changes in amyloid-β levels can be forecasted based on basic sleep patterns.
  • This suggests that improving sleep could potentially be a factor in managing cognitive health as we age.
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Auditory closed-loop stimulation is a non-invasive technique that has been widely used to augment slow oscillations during non-rapid eye movement sleep. Based on the principles of closed-loop stimulation, we developed a novel protocol for manipulating theta activity (3-7 Hz) in rapid eye movement (REM) sleep. Sixteen healthy young adults were studied in two overnight conditions: Stimulation and Sham.

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Emotions have an important survival function. Vast amounts of research have demonstrated how affect-related changes in physiology promote survival by effecting short-term and long-term changes in adaptive behavior. However, if emotions truly serve such an inherent function, they should be pervasive across species and be established early in life.

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Study Objectives: Cortical slow oscillations (SOs) and thalamocortical sleep spindles hallmark slow wave sleep and facilitate memory consolidation, both of which are reduced with age. Experiments utilizing auditory closed-loop stimulation to enhance these oscillations showed great potential in young and older subjects. However, the magnitude of responses has yet to be compared between these age groups.

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Article Synopsis
  • Sleep deprivation increases forgetting rates in episodic memory, affecting how memories are retained.
  • Comparisons showed that forgetting is worse after periods of daytime wakefulness and overnight sleep deprivation compared to a full night of sleep.
  • Notably, sleep deprivation specifically harms the connections between related memories, leading to a different kind of forgetting that doesn’t happen just with daytime wakefulness.
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  • * A total of 29 male children participated in a trial where one night involved stimulation and the other was a placebo, focusing on various memory tasks before and after sleep.
  • * Results showed that while acoustic stimulation increased slow oscillation activity for all children, only those without ADHD showed improved performance on declarative memory tasks, whereas children with ADHD benefitted in procedural memory and working memory tasks.
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  • Closed-loop auditory stimulation (CLAS) enhances slow oscillations (SOs) during sleep by presenting auditory clicks, but the best timing for these clicks is still uncertain.
  • A study with young and older participants showed that clicks applied during the positive phase of SOs increased their amplitude and spindles, with optimal timing being near the SO peak for both age groups.
  • Factors predicting spindle likelihood differ by age: for younger subjects, the phase of the click on the SO was key, while for older subjects, how long it had been since the last spindle was more important.
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Article Synopsis
  • Slow oscillations and delta waves are key brain activity patterns associated with sleep.
  • A study by Kim et al. (2019) used a method called closed-loop optogenetics in rats to investigate these rhythms.
  • The research found that slow oscillations help strengthen memories, while delta waves are linked to the process of forgetting memories.
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Slow oscillations and sleep spindles are hallmarks of the EEG during slow-wave sleep (SWS). Both oscillatory events, especially when co-occurring in the constellation of spindles nesting in the slow oscillation upstate, are considered to support memory formation and underlying synaptic plasticity. The regulatory mechanisms of this function at the circuit level are poorly understood.

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Background: The consolidation of sleep-dependent memories is mediated by an interplay of cortical slow oscillations (SOs) and thalamo-cortical sleep spindles. Whereas an enhancement of SOs with auditory closed-loop stimulation has been proven highly successful, the feasibility to induce and boost sleep spindles with auditory stimulation remains unknown thus far.

New Method: Here we tested the possibility to enhance spindle activity during endogenous SOs and thereby to promote memory consolidation.

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Sleep is essential for health. Slow wave sleep (SWS), the deepest sleep stage hallmarked by electroencephalographic slow oscillations (SOs), appears of particular relevance here. SWS is associated with a unique endocrine milieu comprising minimum cortisol and high aldosterone, growth hormone (GH), and prolactin levels, thereby presumably fostering efficient adaptive immune responses.

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A region of the brain called the putamen has a central role in procedural memory consolidation during sleep.

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