The consolidation of implicit sequence memory in obstructive sleep apnea

Obstructive Sleep Apnea (OSA) Syndrome is a relatively frequent sleep disorder characterized by disrupted sleep patterns. It is a well-established fact that sleep has beneficial effect on memory consolidation by enhancing neural plasticity. Implicit sequence learning is a prominent component of skill learning. However, the formation and consolidation of this fundamental learning mechanism remains poorly understood in OSA. In the present study we examined the consolidation of different aspects of implicit sequence learning in patients with OSA. We used the Alternating Serial Reaction Time task to measure general skill learning and sequence-specific learning. There were two sessions: a learning phase and a testing phase, separated by a 10-hour offline period with sleep. Our data showed differences in offline changes of general skill learning between the OSA and control group. The control group demonstrated offline improvement from evening to morning, while the OSA group did not. In contrast, we did not observe differences between the groups in offline changes in sequence-specific learning. Our findings suggest that disrupted sleep in OSA differently affects neural circuits involved in the consolidation of sequence learning

Narcolepsy type 1 features across the life span: age impact on clinical and polysomnographic phenotype

Study Objectives: Narcolepsy type 1 (NT1) is a chronic neurological disorder typically arising during adolescence and young adulthood. Recent studies demonstrated that NT1 presents with age-specific features, especially in children. With this study we aimed to describe and to compare the clinical pictures of NT1 in different age groups.Methods: In this cross-sectional, multicenter study, 106 untreated patients with NT1 enrolled at the time of diagnosis underwent clinical evaluation, a semistructured interview (including the Epworth Sleepiness Scale), nocturnal video-polysomnography, and the Multiple Sleep Latency Test. Patients were enrolled in order to establish 5 age-balanced groups (childhood, adolescence, adulthood, middle age, and senior).Results: The Epworth Sleepiness Scale score showed a significant increase with age, while self-reported diurnal total sleep time was lower in older and young adults, with the latter also complaining of automatic behaviors in more than 90% of patients. Children reported the cataplexy attacks to be more frequent (> lid in 95% of patients). "Recalling an emotional event," "meeting someone unexpectedly," "stress," and "anger" were more frequently reported in adult and older adult patients as possible triggers of cataplexy. Neurophysiological data showed a higher number of sleep-onset rapid eye movement periods on the Multiple Sleep Latency Test in adolescent compared to senior patients and an age-progressive decline in sleep efficiency.Conclusions: Daytime sleepiness, cataplexy features and triggers, and nocturnal sleep structure showed age-related difference in patients with NT1; this variability may contribute to diagnostic delay and misdiagnosis

Neurobiology of Sleep-Related Movements

Sleep-related movements comprise a broad spectrum of simple and usually stereotyped movements that are sometimes associated with sleep disturbance (insomnia, sleep fragmentation, and non-restorative sleep). They may represent a physiological variant or a sleep disorder, depending on their intensity, frequency, and associated sleep disruption degree. Sleep-related movements involve usually the lower limbs; they can be idiopathic or associated with other sleep disorders, neurological disease, and medical condition or occur as a consequence of drug use. Several pathophysiological hypotheses have been proposed, but for the majority of these disorders, the neurobiological mechanism is far from being completely understood. Further studies are needed to elucidate the pathophysiology of sleep-related movements in order to better appreciate their clinical significance. This chapter describes the neurobiology of sleep-related movements, namely, periodic limb movements, alternating leg muscle activation, hypnagogic foot tremor, high-frequency myoclonus, excessive fragmentary myoclonus, propriospinal myoclonus at sleep onset, neck myoclonus during sleep, sleep bruxism, sleep-related rhythmic movement disorder, sleep-related leg cramps, and sleep starts. We also present a mechanistic model of the potential role of the spinal central pattern generator for locomotion in generating the leg movements