Elsevier

Pathologie Biologie

Volume 62, Issue 5, October 2014, Pages 241-251
Pathologie Biologie

Insomnia and sleep misperceptionInsomnie et mésestimation du sommeil

https://doi.org/10.1016/j.patbio.2014.07.003Get rights and content

Abstract

Sleep misperception is often observed in insomnia individuals (INS). The extent of misperception varies between different types of INS. The following paper comprised sections which will be aimed at studying the sleep EEG and compares it to subjective reports of sleep in individuals suffering from either psychophysiological insomnia or paradoxical insomnia and good sleeper controls. The EEG can be studied without any intervention (thus using the raw data) via either PSG or fine quantitative EEG analyses (power spectral analysis [PSA]), identifying EEG patterns as in the case of cyclic alternating patterns (CAPs) or by decorticating the EEG while scoring the different transient or phasic events (K-Complexes or sleep spindles). One can also act on the on-going EEG by delivering stimuli so to study their impact on cortical measures as in the case of event-related potential studies (ERPs). From the paucity of studies available using these different techniques, a general conclusion can be reached: sleep misperception is not an easy phenomenon to quantify and its clinical value is not well recognized. Still, while none of the techniques or EEG measures defined in the paper is available and/or recommended to diagnose insomnia, ERPs might be the most indicated technique to study hyperarousal and sleep quality in different types of INS. More research shall also be dedicated to EEG patterns and transient phasic events as these EEG scoring techniques can offer a unique insight of sleep misperception.

Résumé

La mésestimation du sommeil est souvent observée chez les individus souffrant d’insomnie (INS). Cependant, l’ampleur de cette mésestimation varie entre les types d’INS. Cet article est composé de sections dédiées à l’étude de l’EEG et sa comparaison avec les rapports subjectifs de sommeil d’individus souffrant soit d’insomnie psychophysiologique ou paradoxale et bons dormeurs. L’EEG peut être étudié soit sans intervention (en utilisant les données brutes) comme dans le cas de la polysomnographie ou l’analyse spectrale, soit en identifiant des patrons d’activation comme pour les patrons cycliques alternants (cyclic alternating pattern) ou encore en décortiquant l’EEG en évènements phasiques ou transitoires (complexes-K et fuseaux de sommeil). On peut également agir sur l’EEG en délivrant des sons et en étudiant leur impact sur les ondes de l’EEG comme dans le cas des potentiels évoqués, et surtout ceux cognitifs. Du peu d’études disponibles utilisant ces différentes techniques/mesures, une conclusion générale peut tout de même être tirée : la mésestimation du sommeil n’est pas facilement quantifiable et sa valeur clinique n’est pas adéquatement reconnue. Alors qu’aucune des techniques/mesures définies ici n’est disponible ou recommandée afin de diagnostiquer l’insomnie, la technique utilisant les potentiels évoqués cognitifs semble la plus appropriée ou juste afin de mesurer l’hypervigilance corticale (hyperarousal) et la qualité du sommeil chez les différents types d’individus souffrant d’insomnie. Finalement, plus de recherches devraient être dédiées à l’étude des patrons EEG et des évènements phasiques du sommeil puisque ces techniques apportent une compréhension différemment unique de la mésestimation du sommeil.

Section snippets

Abbreviations

    CAPs

    Cyclic alternating patterns

    DSM-5

    Diagnostic and Statistical Manual of Mental Disorders – Version 5

    EEG

    Electroencephalogram or electroencephalography

    EKC

    Evoked K-Complex

    EOG

    Electrooculography

    EMG

    Electromyography

    ERPs

    Event-related potentials

    FFT

    Fast Fourier Transformations

    fMRI

    functional Magnetic Resonance Imagery (MRI)

    GS

    Good sleepers

    ICSD

    International Classification of Sleep Disorders

    INS

    Individuals suffering from insomnia

    KC

    K-Complex

    NCAP

    Non-CAP

    NREM

    Non-rapid eye movement

    N1

    Negative wave appearing about

Definition and types of insomnia

An insomnia disorder is defined as a complaint of prolonged sleep latency (labeled “sleep-onset insomnia”), difficulties in maintaining sleep (labeled “sleep-maintenance insomnia”), waking up too early in the morning (labeled “terminal insomnia”), and a mix of different sleep complaints (labeled “mixed insomnia”). In addition, the DSM-5 [6] specifies that to be considered a disorder, insomnia or its perceived consequences cause clinically marked distress or significant impairment of

Sleep diary

A detailed clinical history/assessment of the patient's subjective complaint will significantly benefit complementary data from more systematic sources such neurophysiological and neuropsychological assessments. Sleep diary monitoring is an exceptional tool to document the perceived severity of insomnia. A sleep diary commonly requires self-recording of bedtime and arising time, along with morning estimates of sleep-onset latency, number and duration of awakenings, total sleep time, and several

Polysomnography (PSG)

Insomnia protocols are usually conducted on two or three consecutive nights of PSG recordings. Usual PSG recordings include electroencephalography (EEG), electrooculography (EOG) and electromyography (EMG). PSG has two main objectives:

  • codify the different NREM sleep (stages 1, 2, 3 and 4) and REM sleep (Fig. 1);

  • screen for sleep disorders and quantify their respective severities.

One important limitation of PSG is that it does not provide a valid sample of an individual's typical sleep, and

Event-related potentials (ERPs)

An external physical stimulus or internal psychological event elicits small amplitude changes in the EEG, therefore providing a means to “probe” the extent of information processing within the nervous system during wake and sleep. Contrary to neuroimaging, which has an excellent spatial resolution, event-related potentials (ERPs) have a high temporal resolution (about one tenth of a millisecond). ERP components are classified according to their latencies: early components (<80 ms approximately)

Power spectral analysis (PSA)

PSA consists of Fast Fourier Transformations (FFT) revealing frequencies (measured in Hz) and amplitudes (measured in μV) of the waves constituting the different sleep stages. Averages of different frequency bands are calculated with bands usually defined as follow: slow wave (0–1 Hz), delta (1–4 Hz), theta (4–7 Hz), alpha (7–11 Hz), sigma (11–14 Hz), beta1 (14–20 Hz), beta2 (20–35 Hz), gamma (35–60 Hz) and omega (60–125 Hz). Generally, rapid frequency bands (14–125 Hz) characterize elevated cortical

Cyclic alternating patterns (CAPs)

The various stimuli, both internal and external, present during nighttime require sleepers to monitor them in order to adapt their vigilance consequently. This monitoring is possibly due to continuous fluctuations of the cortical activation levels. These fluctuations can be detected through phasic events which range from slow rhythms without macrostructural perturbation of sleep to fast rhythms that are associated with sleep fragmentation [50].

During NREM sleep, Terzano et al. [51] observed a

K-Complex

The K-Complex (KC) can occur spontaneously (spontaneous KC–SKC) or be evoked by a stimulus (evoked KC–EKC) [64], [65]. The EKC and SKC are virtually identical and seem to be induced by both external and internal stimulation [66], [67], [68]. This transient and phasic phenomenon is characteristic of NREM sleep and occurs every two to three minutes, though the frequency of occurrence varies greatly both within and between normal sleepers. In line with the definition of Rechtschaffen and Kales [69]

Spindles

Sleep spindles consist of an EEG burst, oscillating between 11 and 15 cycles per second (Hz) and lasting at least half a second. Even though they occur during S2 and SWS, they are hallmarks of S2 sleep [87]. Their apparition in the EEG indicates that the person has fallen asleep [69]. Sleep spindles are considered to play a role as sleep-protective mechanisms [69], [87], [88] and are implicated in sensorial treatment inhibition, specifically disengagement of disturbing and/or intrusive stimuli

Conclusion

Although many studies on insomnia have been conducted so far, only a paucity of them directly addresses the question of sleep perception, or misperception. This is rather peculiar as the clinical feature of this disorder is mainly based on the subjective report of sleep difficulties, which are themselves not adequately confirmed by sleep research gold standard, polysomnography. In this paper, we have reviewed the empirical evidence of the presence of neurophysiological characteristics,

Disclosure of interest

The authors declare that they have no conflicts of interest concerning this article.

Disclosure statement: This was not an industry-supported study. This study was supported by the Canadian Institutes of Health Research (CIHR # 49500, 86571). The authors have indicated no financial conflicts of interest. The study was conducted at Laboratoire de neurosciences comportementales humaines du Centre de recherche de l’institut universitaire en santé mentale de Québec, Québec, Canada.

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