Les micro-éveils chez l'homme : étude par enregistrements intracérébraux

Wakefulness, non rapid eye movement (NREM) and rapid eye movement (REM) sleep are characterized by specific brain activities. However, recent experimental findings as well as various clinical conditions (parasomnia, sleep inertia) have revealed the presence of transitional states. Brief intrusions of wakefulness into sleep, namely arousals, appear as relevant phenomena to characterize how brain commutes from sleep to wakefulness. Using intra-cerebral recordings in 8 drug-resistant epileptic patients we analyzed electroencephalographic (EEG) activity during spontaneous or nociceptive-induced arousals in NREM and REM sleep. Wavelet spectral analyses were performed to compare EEG signals during arousals, sleep and wakefulness, simultaneously in the thalamus, and primary, associative or high order cortical areas. We observed that: 1) thalamic activity during arousals is stereotyped and its spectral composition corresponds to a state in-between wakefulness and sleep 2) patterns of cortical activity during arousals are heterogeneous, their manifold spectral composition being related to several factors such as sleep stages, cortical areas, arousal modality ("spontaneous" vs nociceptive-induced) and homeostasis; 3) spectral compositions of EEG signals during arousal and wakefulness differ from each other. Thus, stereotyped arousals at the thalamic level seem to be associated with different patterns of cortical arousals due to various regulation factors. These results suggest that human cortex does not shift from sleep to wake in an abrupt binary way. Arousals may be considered more as different states of the brain than as "short awakenings". This phenomenon may reflect the mechanisms involved in the compromise needed to be found between two main contradictory functional necessities, preserving the continuity of sleep and maintaining the possibility to reactTrois états de vigilance, caractérisés par une activité cérébrale spécifique, sont habituellement décrits chez l'Homme: la veille, le sommeil lent et le sommeil paradoxal. Cependant, certaines situations cliniques comme les parasomnies ou l'inertie de sommeil, ainsi que des travaux expérimentaux récents chez l'animal et chez l'homme, suggèrent la possibilité d'états intermédiaires ou transitionnels. L'étude des micro- éveils apparait pertinente pour appréhender les phénomènes de transition entre états de vigilance. Pour caractériser les micro-éveils chez l'Homme, nous avons enregistré l'activité EEG au cours de micro-éveils "spontanés" ou déclenchés par des stimulations nociceptives, en sommeil lent et en sommeil paradoxal, chez 8 patients épileptiques pharmaco-résistants bénéficiant d'un bilan pré-chirurgical invasif stéréo-électro- encéphalographique. Les puissances spectrales dans différentes bandes de fréquence au cours des micro-éveils ont été comparées à celles déterminées sur le signal précèdant le micro-éveil. Le thalamus (pulvinar médian), le cortex sensorimoteur primaire et plusieurs aires corticales associatives ont été étudiés. Nous avons observé 1) une grande reproductibilité intra et interindividuelle des modifications d'activité EEG associées aux micro-éveils dans le thalamus, et qui correspondent à un état intermédiaire entre la veille et le sommeil. 2) une importante hétérogénéité des modes d'activation corticale au cours des micro-éveils, quand bien même l'activation sous- corticale est stéréotypée. Différents facteurs participent à cette variabilité : le cortex considéré, le stade de sommeil au cours duquel le micro-éveil survient, la nature du stimulus à l'origine du micro-éveil, ou encore des phénomènes homéostatiques. 3) que la composition spectrale du signal au cours des micro-éveils dansle cortex était différente de l'état de veille, ce qui situe les micro-éveils hors du spectre des états de vigilance classiquement différenciés et constitue un argument en faveur du fait que la transition entre le sommeil et la veille au niveau cortical ne se fait pas de façon abrupte et binaire. Ainsi, les micro-éveils apparaissent comme des états d'activation cérébrale régulés au moins en partie localement par des mécanismes impliqués dans la gestion d'une double nécessité théoriquement contradictoire : permettre au dormeur de réagir à des stimulations pertinentes, tout en préservant la continuité du sommei

Internet-Based Intervention for Posttraumatic Stress Disorder:Using Remote Imagery Rehearsal Therapy to Treat Nightmares

No abstract availabl

Intracerebral dynamics of sleep arousals : a combined scalp-intracranial EEG study

As an intrinsic component of sleep architecture, sleep arousals represent an intermediate state between sleep and wakefulness and are important for sleep-wake regulation. They are defined in an all-or-none manner, whereas they actually present a wide range of scalp-electroencephalography (EEG) activity patterns. It is poorly understood how these arousals differ in their mechanisms. Stereo-EEG (SEEG) provides the unique opportunity to record intracranial activities in superficial and deep structures in humans. Using combined polysomnography and SEEG, we quantitatively categorized arousals during nonrapid eye movement sleep into slow wave (SW) and non-SW arousals based on whether they co-occurred with a scalp-EEG SW event. We then investigated their intracranial correlates in up to 26 brain regions from 26 patients (12 females). Across both arousal types, intracranial theta, alpha, sigma, and beta activities increased in up to 25 regions ( p  < 0.05; d  = 0.06-0.63), while gamma and high-frequency (HF) activities decreased in up to 18 regions across the five brain lobes ( p  < 0.05; d  = 0.06-0.44). Intracranial delta power widely increased across five lobes during SW arousals ( p  < 0.05 in 22 regions; d  = 0.10-0.39), while it widely decreased during non-SW arousals ( p  < 0.05 in 19 regions; d  = 0.10-0.30). Despite these main patterns, unique activities were observed locally in some regions such as the hippocampus and middle cingulate cortex, indicating spatial heterogeneity of arousal responses. Our results suggest that non-SW arousals correspond to a higher level of brain activation than SW arousals. The decrease in HF activities could potentially explain the absence of awareness and recollection during arousals

Beyond the waves: what does the EEG still hold one century after H. Berger?

The interactions between epilepsy and sleep are numerous and the impact of epilepsy on cognition is well documented. Epilepsy is therefore likely to influence dreaming as one sleep-related cognitive activity. The frequency of dream recall is indeed decreased in patients with epilepsy, especially in those with primary generalized seizures. The content of dreams is also disturbed in epilepsy patients, being more negative and with more familiar settings. While several confounding factors (anti-seizure medications, depression and anxiety disorders, cognitive impairment) may partly account for these changes, some observations suggest an effect of seizures themselves on dreams. Indeed, the incorporation of seizure symptoms in dream content has been described, concomitant or not with a focal epileptic discharge during sleep, suggesting that epilepsy might directly or indirectly interfere with dreaming. These observations, together with current knowledge on dream neurophysiology and the links between epilepsy and sleep, suggest that epilepsy may impact not only wake- but also sleep-related cognition

Arousals in human sleep : a stereo-electroencephalographic study

Trois états de vigilance, caractérisés par une activité cérébrale spécifique, sont habituellement décrits chez l'Homme: la veille, le sommeil lent et le sommeil paradoxal. Cependant, certaines situations cliniques comme les parasomnies ou l'inertie de sommeil, ainsi que des travaux expérimentaux récents chez l'animal et chez l'homme, suggèrent la possibilité d'états intermédiaires ou transitionnels. L'étude des micro- éveils apparait pertinente pour appréhender les phénomènes de transition entre états de vigilance. Pour caractériser les micro-éveils chez l'Homme, nous avons enregistré l'activité EEG au cours de micro-éveils "spontanés" ou déclenchés par des stimulations nociceptives, en sommeil lent et en sommeil paradoxal, chez 8 patients épileptiques pharmaco-résistants bénéficiant d'un bilan pré-chirurgical invasif stéréo-électro- encéphalographique. Les puissances spectrales dans différentes bandes de fréquence au cours des micro-éveils ont été comparées à celles déterminées sur le signal précèdant le micro-éveil. Le thalamus (pulvinar médian), le cortex sensorimoteur primaire et plusieurs aires corticales associatives ont été étudiés. Nous avons observé 1) une grande reproductibilité intra et interindividuelle des modifications d'activité EEG associées aux micro-éveils dans le thalamus, et qui correspondent à un état intermédiaire entre la veille et le sommeil. 2) une importante hétérogénéité des modes d'activation corticale au cours des micro-éveils, quand bien même l'activation sous- corticale est stéréotypée. Différents facteurs participent à cette variabilité : le cortex considéré, le stade de sommeil au cours duquel le micro-éveil survient, la nature du stimulus à l'origine du micro-éveil, ou encore des phénomènes homéostatiques. 3) que la composition spectrale du signal au cours des micro-éveils dansle cortex était différente de l'état de veille, ce qui situe les micro-éveils hors du spectre des états de vigilance classiquement différenciés et constitue un argument en faveur du fait que la transition entre le sommeil et la veille au niveau cortical ne se fait pas de façon abrupte et binaire. Ainsi, les micro-éveils apparaissent comme des états d'activation cérébrale régulés au moins en partie localement par des mécanismes impliqués dans la gestion d'une double nécessité théoriquement contradictoire : permettre au dormeur de réagir à des stimulations pertinentes, tout en préservant la continuité du sommeilWakefulness, non rapid eye movement (NREM) and rapid eye movement (REM) sleep are characterized by specific brain activities. However, recent experimental findings as well as various clinical conditions (parasomnia, sleep inertia) have revealed the presence of transitional states. Brief intrusions of wakefulness into sleep, namely arousals, appear as relevant phenomena to characterize how brain commutes from sleep to wakefulness. Using intra-cerebral recordings in 8 drug-resistant epileptic patients we analyzed electroencephalographic (EEG) activity during spontaneous or nociceptive-induced arousals in NREM and REM sleep. Wavelet spectral analyses were performed to compare EEG signals during arousals, sleep and wakefulness, simultaneously in the thalamus, and primary, associative or high order cortical areas. We observed that: 1) thalamic activity during arousals is stereotyped and its spectral composition corresponds to a state in-between wakefulness and sleep 2) patterns of cortical activity during arousals are heterogeneous, their manifold spectral composition being related to several factors such as sleep stages, cortical areas, arousal modality ("spontaneous" vs nociceptive-induced) and homeostasis; 3) spectral compositions of EEG signals during arousal and wakefulness differ from each other. Thus, stereotyped arousals at the thalamic level seem to be associated with different patterns of cortical arousals due to various regulation factors. These results suggest that human cortex does not shift from sleep to wake in an abrupt binary way. Arousals may be considered more as different states of the brain than as "short awakenings". This phenomenon may reflect the mechanisms involved in the compromise needed to be found between two main contradictory functional necessities, preserving the continuity of sleep and maintaining the possibility to reac

Seizures and epilepsy after intracerebral hemorrhage: an update

International audienceSeizures are common after intracerebral hemorrhage, occurring in 6 to 15% of the patients, mostly in the first 72 hours. Their incidence reaches 30% when subclinical or non-convulsive seizures are diagnosed by continuous electroencephalogram. Several risk factors for seizures have been described including cortical location of intracerebral hemorrhage, presence of intraventricular hemorrhage, total hemorrhage volume, and history of alcohol abuse. Seizures after intracerebral hemorrhage may theoretically be harmful as they can lead to sudden blood pressure fluctuations, increase intracranial pressure and neuronal injury due to increased metabolic demand. Some recent studies suggest that acute symptomatic seizures (occurring within seven days of stroke) are associated with worse functional outcome and increased risk of death despite accounting for other known prognostic factors such as age and baseline hemorrhage volume. However, the impact of seizures on prognosis is still debated and it remains unclear if treating or preventing seizures might lead to improved clinical outcome. Thus, the currently available scientific evidence does not support the routine use of antiseizure medication as primary prevention among patients with intracerebral hemorrhage. Only prospective adequately powered randomized controlled trials will be able to answer whether seizure prophylaxis in the acute or longer term settings is beneficial or not in patients with intracerebral hemorrhage

Spotlight on Sleep Stage Classification Based on EEG

The recommendations for identifying sleep stages based on the interpretation of electrophysiological signals (electroencephalography [EEG], electro-oculography [EOG], and electromyography [EMG]), derived from the Rechtschaffen and Kales manual, were published in 2007 at the initiative of the American Academy of Sleep Medicine, and regularly updated over years. They offer an important tool to assess objective markers in different types of sleep/wake subjective complaints. With the aims and advantages of simplicity, reproducibility and standardization of practices in research and, most of all, in sleep medicine, they have overall changed little in the way they describe sleep. However, our knowledge on sleep/wake physiology and sleep disorders has evolved since then. High-density electroencephalography and intracranial electroencephalography studies have highlighted local regulation of sleep mechanisms, with spatio-temporal heterogeneity in vigilance states. Progress in the understanding of sleep disorders has allowed the identification of electrophysiological biomarkers better correlated with clinical symptoms and outcomes than standard sleep parameters. Finally, the huge development of sleep medicine, with a demand for explorations far exceeding the supply, has led to the development of alternative studies, which can be carried out at home, based on a smaller number of electrophysiological signals and on their automatic analysis. In this perspective article, we aim to examine how our description of sleep has been constructed, has evolved, and may still be reshaped in the light of advances in knowledge of sleep physiology and the development of technical recording and analysis tools. After presenting the strengths and limitations of the classification of sleep stages, we propose to challenge the "EEG-EOG-EMG" paradigm by discussing the physiological signals required for sleep stages identification, provide an overview of new tools and automatic analysis methods and propose avenues for the development of new approaches to describe and understand sleep/wake states

Relationship Between Epilepsy and Dreaming: Current Knowledge, Hypotheses, and Perspectives

The interactions between epilepsy and sleep are numerous and the impact of epilepsy on cognition is well documented. Epilepsy is therefore likely to influence dreaming as one sleep-related cognitive activity. The frequency of dream recall is indeed decreased in patients with epilepsy, especially in those with primary generalized seizures. The content of dreams is also disturbed in epilepsy patients, being more negative and with more familiar settings. While several confounding factors (anti-seizure medications, depression and anxiety disorders, cognitive impairment) may partly account for these changes, some observations suggest an effect of seizures themselves on dreams. Indeed, the incorporation of seizure symptoms in dream content has been described, concomitant or not with a focal epileptic discharge during sleep, suggesting that epilepsy might directly or indirectly interfere with dreaming. These observations, together with current knowledge on dream neurophysiology and the links between epilepsy and sleep, suggest that epilepsy may impact not only wake- but also sleep-related cognition