Insomnia and sleep misperceptionInsomnie et 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);
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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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2021, International Journal of PsychophysiologyCitation Excerpt :A heightened activity in hypothalamic-pituitary-adrenal axis resulting in sympathetic nervous system hyperactivity is widely accepted as the main perpetuating factor in sleep and wake dysfunction in insomnia. This hyperarousal model of insomnia may actually explain, in part, the discrepancy between the subjective and objective sleep measures (Bastien et al., 2014). Polysomnographic studies have reported a correlation between the autonomic nervous system activity and EEG characteristics, demonstrating a link between sleep misperception and increased cortical activity in primary insomnia, being more pronounced in paradoxical insomnia (Maes et al., 2014; Krystal et al., 2002).