Sleep Science
Gia Merlo, Kathy Berra in Lifestyle Nursing, 2023
Sleep and wakefulness are under homeostatic and circadian alerting control. Homeostatic control refers to the phenomenon that the longer we are awake or not experiencing specific sleep stages, the greater the drive to make up for the lost sleep or sleep stage. This is referred to as “sleep drive.” Circadian control of the sleep–wake rhythm consists of biochemical, physiological, and behavioral processes that encourage wakefulness and is referred to as the “circadian alerting rhythm.” When these two regulatory mechanisms are working in synchrony, patients are able to enter into sleep at regular times each evening, experience deeper stages of sleep (i.e., N3 sleep), and remain asleep until it is time to awake and arise from bed feeling rested. Unfortunately, these two main regulators of sleep can be disrupted by behaviors that increase alertness and wakefulness when sleep is desired. Working with patients to improve their sleep should begin with a brief description of the physiological and psychological factors that cause the initiation and maintenance of sleep and wakefulness: (1) sleep drive, (2) circadian alerting rhythm, (3) physiological arousal, (4) cognitive arousal, and (5) sleep environment, followed by the behaviors that affect these factors. We present each sleep management principle and its associated guidelines below.
The Neurological Examination
Richard A. Jonas, Jane W. Newburger, Joseph J. Volpe, John W. Kirklin in Brain Injury and Pediatric Cardiac Surgery, 2019
The general level of alertness is one of the most sensitive indices of global neurological function. It is dependent on the integrity of several levels of the central nervous system. The level of alertness of the normal infant will vary according to a number of factors including the time of last feeding, environmental stimuli, recent experiences, and gestational age. Prior to 28 weeks gestation it is difficult to identify periods of wakefulness. At approximately 28 weeks there is a distinct change in the level of alertness. Gentle stimuli result in several minutes of alertness and there may be spontaneous periods of wakefulness. By 32 weeks the eyes are frequently open and spontaneous roving eye movements appear. By 36 weeks increased alertness can be observed and vigorous crying appears during wakefulness. By term the infant exhibits periods of attention to visual and auditory stimuli, and it is possible to study sleep-waking patterns in detail.5
The neurobiology of sleep
Philip N. Murphy in The Routledge International Handbook of Psychobiology, 2018
As described above, wakefulness is made possible by the activity of specific brain structures. This activity must therefore be inhibited to allow sleep onset, and a number of mechanisms may be involved. In the anterior part of the hypothalamus, several groups of neurons are selectively active during sleep. Some of these groups are clustered in the median preoptic nucleus (MnPO), which is thought to have an important role in triggering sleep onset. Moreover, an estimated 40% of the MnPO’s neurons use the well-known inhibitory neurotransmitter gamma aminobutyric acid (GABA) (Gong et al., 2004; Gvilia, Angara, McGinty, & Szymusiak, 2005). These neurons are connected to several wake-promoting regions, including the locus coeruleus and the dorsal raphe nucleus; the results of animal studies have confirmed that the MnPO’s neurons can inhibit these structures (Suntsova et al., 2007). These data support the hypothesis whereby the MnPO is responsible for sleep onset (Suntsova, Szymusiak, Alam, Guzman-Marin, & McGinty, 2002). Even though it has been proposed that the MnPO’s only hypnic function is to trigger sleep onset, Benedetto and colleagues found that pharmacological inhibition of this structure not only prevents NREM sleep but also inhibits REM sleep and promotes awakening in sleeping cats (Benedetto, Chase, & Torterolo, 2012). Therefore, it is currently thought that the MnPO promotes both sleep onset and sleep maintenance.
Sleep disruption induces activation of inflammation and heightens risk for infectious disease: Role of impairments in thermoregulation and elevated ambient temperature
Published in Temperature, 2023
Michael R. Irwin
Over the course of the sleep period, humans show a transition from wakefulness to entry into NREM sleep, followed by transition to REM sleep. (Figure 1) At the end of a REM period, a brief arousal or awakening may occur, followed by entry into another NREM sleep period. This cycle from NREM sleep to REM sleep, with each cycle lasting about 80 to 110 minutes, typically repeats four to six times over the course of the night. Additionally, during the early part of the night, sleep architecture reveals that NREM phase is predominated by N3 or SWS, and episodes of REM episodes are short. In contrast, during the latter part of the night, REM episodes are longer and more frequent. Whereas scoring dimensions might suggest that sleep is a quantal behavioral state [37], brain activity shows a continuous progression across the NREM domain from wakefulness to deep sleep. Indeed, spectral analytic methods reveal continuous shifting of mixed EEG frequencies to predominately lower EEG frequencies in the transition from awake to NREM sleep and N3 sleep [39]. Slow-wave activity (SWA), a measure of the density and amplitude of slow waves, is thought to capture the depth of sleep and is markedly increased after prolonged period of wakefulness [40], with potential effects on recovery of immune response following sleep loss [41].
Inhibitory Deficits of Insomnia Disorder: A Meta-Analysis on Event Related Potentials in Auditory Oddball Task
Published in Behavioral Sleep Medicine, 2023
Liyong Yu, Lu Yang, Hao Xu, Guangli Zhao, Zeyang Dou, Yucai Luo, Jie Yang, Qi Zhang, Siyi Yu
A meta-analysis was conducted to gain a general understanding of the N1 component, considering both deviant and standard stimuli. Within each stimulus type, subgroup analysis was conducted based on the sleep stage (wakefulness, NREM, and REM). The results showed that, compared to healthy controls, individuals with insomnia did not exhibit any significant difference in response to deviant stimuli, and a significant level of heterogeneity was observed (Figure 2a). A subgroup analysis of the wakefulness stage in response to deviant stimuli indicated a significantly lower amplitude in individuals with insomnia, with a low level of heterogeneity. In response to standard stimuli, individuals with insomnia did not exhibit any significant differences compared to healthy controls, with a low level of heterogeneity (Figure 2b). The subgroup analysis of the response to standard stimuli across sleep stages showed no significant differences between individuals with insomnia and healthy controls.
The effect of time of day and high intensity exercise on cognitive performances of elite adolescent karate athletes
Published in Chronobiology International, 2022
Syrine Khemila, Mohamed Romdhani, Salma Abedelmalek, Hamdi Chtourou, Mohamed Abdelkader Souissi, Emna BenTouati, Nizar Souissi
An improvement in cognitive performance (i.e., SRT, CRT and MRT) was observed following KST only in the morning. These findings are in line with the results of a recent review study who found that professional athletes’ cognitive function improved after exercise induced fatigue (Gus Almonroeder et al. 2018). In the current study, it could be suggested that Karate athletes are more resistant to physical stress in the morning after the effort compared to the afternoon. However, it is difficult to explain this result. A possible explanation is that alertness and wakefulness are low in the morning. Physical exercise could therefore increase these parameters by its action on hormones that stimulate wakefulness such as cortisol. More physiological variables, such as heart rate, lactate levels, and hormones (e.g., cortisol, adrenalin, and noradrenalin), must also be measured to validate the relationship between cognitive performance and the activation induced by physical exercise.