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Chronobiology is the study of biological rhythms. Biological rhythms are driven endogenously in the form of biochemical or physiological processes and are altered by external cues or stimuli.1 These external environmental cues or stimuli are the zeitgebers, the important one of these cues is daylight. Zeitgebers the stimuli which are capable to entrain/alter circadian rhythms.2 The daily rhythms have been observed not only in mammals but also in plants, fungi, and cyanobacteria.3 Recent studies have shown that the pacemaker for daily rhythms is located in the supra-chiasmatic nucleus (SCN) of the hypothalamus in the brain.4 When the SCN is stimulated by any zeitgeber like light, temperature, etc. from the surroundings, it sets the principal timing cues to synchronize the circadian rhythms of different proteins in brain tissues.5 It has been widely studied that proteins are responsible not only for making cell structures but also involved in physiological functioning. So, depending on time of the day, the physiological functioning is altered which further leads to the alteration of the behaviours.  Chronopsychology Chronopsychology can be defined as the study of behaviors that oscillate rhythmically with time. These behaviors may have circadian (about 24 hours), infradian (more than 24 hours), and ultradian (less than 24 hours) rhythms. Additionally, it has been reported that there are seasonal variations as well as due to altered environmental zeitgebers leading to altered proteins and physiology.6 In this way, the altered profile of proteins and physiological parameters, leads to altered behaviors.7 Studies have indicated that due to significant daily alteration of biological molecules at cellular levels, may lead to daily variation in mood which may be responsible for the development of mood disorders including depression, mild depression, and seasonal affective disorder.8 The gap in psychotherapy? As literature confirms that there are daily alteration of biochemicals including brain proteins which may alter respective physiological activities. So, due to the time-dependent alteration of certain physiological parameters, the linked behaviors may fluctuate at other time points of the day. As studies have shown that various brain neurotransmitters that are involved especially in cognition like dopamine show daily variations.9-10 Due to the daily variation of neurotransmitters, psychological functioning may show daily variations and it is indicated that circadian rthytms disruption may lead to mental health issues.11 Studies have shown that physiological functions like memory performance and learning follow a daily rhythm.12 So, if the disruption of the circadian rhythm leads to mental health issues, that means health issues may have time dependency. As physiological, psychological, and mental health issues have shown daily rhythms, so psychotherapeutic intervention may have a different time-dependent effect. Effective approach As discussed above, physiological parameters may fluctuate during 24 hours of the day due to specific protein levels at the specific time of the day. This variation may lead to altering certain behaviors. So, any psychotherapeutic intervention aimed at managing behavior may produce better outcomes when planned at a certain time slot of the day that needs to be studied. However, studies have shown that different cognitive skills including learning, memory are due to neurotrophic factors that show daily variation with a peak in the morning time slots.13 So, if any psychotherapeutic session aimed for augmenting cognitive skills may be accomplished in the morning time slots for better outcomes. Psychotherapy is aimed at suggesting the client and hyper suggestibility is observed with slow brain waves, especially in the prefrontal cortex. The peak of circadian variation of alpha brain waves (0-12 Hz) is linked with low body temperature14 and circadian rhythms of low body temperature are the evening hours. So, it may be assumed that psychotherapy aimed to increase suggestibility like hypnotherapy should be conducted in the evening hours as compared to morning hours. The suggestions in the mornings may be resisted due to the peak levels of cortisol, as cortisol is linked to distress which makes people more critical and suggestibility may be reduced. The author names this time-based psychotherapeutic intervention as chronopsychotherapy. Therefore, understanding the basic principles of chronobiology can help how biological processes follow rhythms and how this impacts therapeutic intervention. So, it may be concluded that therapeutic intervention either pharmacological or psychological may have different outcomes at different time points of the day that needs to be explored and certain empirical studies should be conducted to validate this concept of chronopsychotherapy.

Chronobiology is the study of biological rhythms. Biological rhythms are driven endogenously in the form of biochemical or physiological processes and are altered by external cues or stimuli.1 These external environmental cues or stimuli are the zeitgebers, the important one of these cues is daylight. Zeitgebers the stimuli which are capable to entrain/alter circadian rhythms.2 The daily rhythms have been observed not only in mammals but also in plants, fungi, and cyanobacteria.3 Recent studies have shown that the pacemaker for daily rhythms is located in the supra-chiasmatic nucleus (SCN) of the hypothalamus in the brain.4 When the SCN is stimulated by any zeitgeber like light, temperature, etc. from the surroundings, it sets the principal timing cues to synchronize the circadian rhythms of different proteins in brain tissues.5 It has been widely studied that proteins are responsible not only for making cell structures but also involved in physiological functioning. So, depending on time of the day, the physiological functioning is altered which further leads to the alteration of the behaviours.  Chronopsychology Chronopsychology can be defined as the study of behaviors that oscillate rhythmically with time. These behaviors may have circadian (about 24 hours), infradian (more than 24 hours), and ultradian (less than 24 hours) rhythms. Additionally, it has been reported that there are seasonal variations as well as due to altered environmental zeitgebers leading to altered proteins and physiology.6 In this way, the altered profile of proteins and physiological parameters, leads to altered behaviors.7 Studies have indicated that due to significant daily alteration of biological molecules at cellular levels, may lead to daily variation in mood which may be responsible for the development of mood disorders including depression, mild depression, and seasonal affective disorder.8 The gap in psychotherapy? As literature confirms that there are daily alteration of biochemicals including brain proteins which may alter respective physiological activities. So, due to the time-dependent alteration of certain physiological parameters, the linked behaviors may fluctuate at other time points of the day. As studies have shown that various brain neurotransmitters that are involved especially in cognition like dopamine show daily variations.9-10 Due to the daily variation of neurotransmitters, psychological functioning may show daily variations and it is indicated that circadian rthytms disruption may lead to mental health issues.11 Studies have shown that physiological functions like memory performance and learning follow a daily rhythm.12 So, if the disruption of the circadian rhythm leads to mental health issues, that means health issues may have time dependency. As physiological, psychological, and mental health issues have shown daily rhythms, so psychotherapeutic intervention may have a different time-dependent effect. Effective approach As discussed above, physiological parameters may fluctuate during 24 hours of the day due to specific protein levels at the specific time of the day. This variation may lead to altering certain behaviors. So, any psychotherapeutic intervention aimed at managing behavior may produce better outcomes when planned at a certain time slot of the day that needs to be studied. However, studies have shown that different cognitive skills including learning, memory are due to neurotrophic factors that show daily variation with a peak in the morning time slots.13 So, if any psychotherapeutic session aimed for augmenting cognitive skills may be accomplished in the morning time slots for better outcomes. Psychotherapy is aimed at suggesting the client and hyper suggestibility is observed with slow brain waves, especially in the prefrontal cortex. The peak of circadian variation of alpha brain waves (0-12 Hz) is linked with low body temperature14 and circadian rhythms of low body temperature are the evening hours. So, it may be assumed that psychotherapy aimed to increase suggestibility like hypnotherapy should be conducted in the evening hours as compared to morning hours. The suggestions in the mornings may be resisted due to the peak levels of cortisol, as cortisol is linked to distress which makes people more critical and suggestibility may be reduced. The author names this time-based psychotherapeutic intervention as chronopsychotherapy. Therefore, understanding the basic principles of chronobiology can help how biological processes follow rhythms and how this impacts therapeutic intervention. So, it may be concluded that therapeutic intervention either pharmacological or psychological may have different outcomes at different time points of the day that needs to be explored and certain empirical studies should be conducted to validate this concept of chronopsychotherapy.

Thermoregulation is an important mechanism to ensure thermal homeostasis. In horses, different housing conditions could influence this mechanism by exposing animals to different microclimates. The circadian rhythm of body temperature is well known. For this reason, we wanted to investigate the daily rhythm of cutaneous (jugular, shoulder, inner thigh and croup) temperature in comparison to rectal temperature in athletic horses kept under two different housing conditions. Ten clinically healthy Italian Saddle horses were divided into two equal groups: the first group was housed in individual boxes, and the second group was kept in paddocks. In all horses, rectal and cutaneous temperature measurements were performed every 4 h for 48 consecutive hours during different seasons (spring, summer, autumn and winter), respectively, by means of digital and infrared thermometers. Ambient temperature, relative humidity and ventilation were recorded simultaneously. A general linear model (GLM) was applied to the recorded temperature values displaying a significant effect of season, time of day, site of recording and housing condition (p < 0.001). No statistical differences were found between the two days of monitoring (p = 0.49). A trigonometric statistical model (single cosinor method) was applied to investigate the circadian rhythm of rectal and cutaneous temperatures in the two different groups. Our results showed circadian rhythmicity of rectal temperature during all seasons and in both groups. Cutaneous temperature shows daily rhythmicity that was different in the various regions and was influenced by housing conditions and seasons. Application of GLM also showed a statistically significant effect of season and site of recording (p < 0.0001) on all circadian parameters and of management condition on amplitude and robustness (p < 0.0001). No statistical differences between the two days of monitoring were observed (p = 0.68). These findings are probably due to the animals’ thermoregulatory mechanisms ensuring heat exchange between the body and the environment, and that was influenced by the microclimate. In particular, the microclimate influenced the thermodispersion disrupting the daily rhythmicity of some body regions, in horses kept in boxes. Only the temperate climatic conditions observed in summer guarantee the expression of the daily rhythmicity of all body surfaces in both management conditions. These results contribute to the knowledge of the mechanisms of homeostasis and control of body temperature in the athletic horse kept in different housing conditions, with a chronophysiological interpretation that completes the proper management of thermal well-being in horses.

A study was undertaken to assess the impact of the timing of grazing on rumen and plasma metabolites and some metabolic hormones in lactating dairy sheep allocated to an Italian ryegrass (Lolium multiflorum Lam) pasture in spring for 4 h/d. Twenty-four mid lactation Sarda ewes stratified for milk yield, body weight, and body condition score, were divided into four homogeneous groups randomly allocated to the treatments (2 replicate groups per treatment). Treatments were morning (AM, from 08:00 to 12:00) and afternoon pasture allocation (PM, from 15:30 to 19:30). Samples of rumen liquor (day 39) and blood plasma (days 17 and 34 of the experimental period) were collected before and after the grazing sessions. Moreover, on days 11 and 35, grazing time was assessed by direct observation and herbage intake measured by the double weighing procedure. Grazing time was longer in PM than AM ewes (P < 0.001) but herbage intake was undifferentiated between groups. The intake of water-soluble carbohydrates at pasture was higher in PM than AM ewes (P < 0.05). The post-grazing propionic and butyric acid concentration, as measured on day 39, were higher in PM than AM ewes (P < 0.05). The basal level of glucose on day 34 and insulin (on both sampling days) were higher in PM than AM (P < 0.05). The opposite trend was detected for non-esterified fatty acids (P < 0.05, day 34) and urea (both days). Pasture allocation in the afternoon rather than in the morning decreased plasma concentration of ghrelin (P < 0.001) and cortisol (P < 0.001), with a smoothed trend on day 34 in the latter variable. To conclude, postponing the pasture allocation to afternoon increased the intake of WSC, favoring a glucogenic pattern of rumen fermentation and a rise of glucose and insulin levels in blood, although these effects were not consistent across the whole experimental period. Moreover, the afternoon grazing decreased the level of cortisol and ghrelin, suggesting a higher satiation-relaxing effect.

Generally, it is assumed that heart-rhythm disorders during hypoxia result from the interplay between the autonomic nervous system (ANS) and the direct effect of hypoxia on cardiorespiratory structures of the central nervous system and on the myocardium. Circadian variability in the ANS may substantially influence the electrical stability of the myocardium, and thus it is associated with the preconditioning protective mechanism. We designed our study using anaesthetized Wistar rats (ketamine/xylazine 100 mg/15 mg/kg, i.m., open chest experiments) to evaluate the effect of preconditioning (PC) induced by 1 to 3 cycles (1 PC–3 PC) of asphyxia (5 min. of artificial hypoventilation, VT = 0.5 ml/100 g of b.w., 20 breaths/min.) and reoxygenation (5 min. of artificial ventilation, VT = 1 ml/100 g of b.w., 50 breaths/min.) on the heart rate (HR) during followed exposure 20 minutes of hypoventilation after adaptation to a light-dark (LD) cycle of 12 hours:12 hours. Hypoxic HR increases were only minimally prevented by 1 to 2 PC pre-treatment, particularly during the dark part of the day. A statistically significant HR increase required 3 PC and was seen only in the light part of the day. We concluded that possible ANS participation in asphyxic preconditioning depends not only on the number of preconditioned cycles but also on the LD cycle, when the ANS participation in preconditioning can be effective only in the light (nonactive) period.

Our goal in this chapter is to familiarize the reader with the nuances of normal sleep and to provide insight into the array of childhood sleep disorders and their diagnosis, management, and treatment. First, we describe the stages of normal sleep, their typical features and signs, and how these change during infancy, through childhood, and into adulthood. Also, summarized are the characteristics and significance of dreams. Then we introduce the notion of sleep hygiene to describe the set of behaviors that influence a person's ability to initiate and maintain sleep. Different approaches to ensure good sleep hygiene can be beneficial, depending on the age of the subject. Quality of a child's sleep can also be influenced by medication, psychological factors, and alterations in the circadian rhythm, and treatment approaches are outlined in each case. We refer to the various medical conditions that can affect sleep, and also describe the dramatic, and sometimes bizarre symptoms of the parasomnias, the most common of which are sleepwalking, night terrors, nightmares, jactatio capitis nocturna, and sleep‐related enuresis. Finally, we recount the cognitive and emotional consequences of sleeplessness in children and adolescents. Case studies are used throughout to illuminate the text.