The Relationship Between Circadian Rhythm-Homeostatic Dual Processes Model And Chronotype

Chronotype is often used to measure individual differences in circadian rhythms or rest-activity,reflecting individual circadian preferences(i.e.,preference for morning or evening time)or individual entrainment phase(Taylor & Hasler,2018),which usually shows a preference for a sleep-wake habit(Horne & Ostberg,1976).Currently,Chronotype is widely used in the fields of cognitive function(Janku et al.,2020),mental illness(Gershon et al.,2018),metabolic health and epidemiology(Almoosawi et al.,2019),shift work(Torsvall& Akerstedt,1980),academic performance(Goldin et al.,2020),motor performance(Montaruli et al.,2017),and et al.Assessment of chronotype is a central task in circadian biology(Roenneberg,2012).At present,the subjective and objective measurement of chronotype are relatively mature.However,the chronotype measurement is influenced by many factors,such as gender,age,sleep quality,insomnia severity,geographical location,etc.In addition,different chronotype measurement tools have a diverse range of application.Compared with MEQ,MCTQ and actigraphy,rMEQ is more convenient,suitable for large samples,and tends to measure the stable characteristics of time pattern.How to measure accurately and effectively becomes an important essential part of chronotype-related research.The mechanism-related studies of chronotype are increasingly rich,and most of the existing related studies focus on the effect of chronotype on individual daily function,such as cognitive performance,vigilance level,emotion,or physical activity.There is no direct and definite conclusion about the mechanism of chronotype.Previous studies found that functional connectivity between the default network(DMN)and the task positive network(ACN,especially the fronto-parietal control network / central executive network,FPN /CEN)may play an important role in the mechanism of chronotype,so the mechanism of chronotype is to be explored based on functional connectivity between large-scale brain networks.In study 1,we examined the subjective and objective consistency of chronotype measurement and identified the appropriate chronotype measurement tool,and further explore the neural mechanism of chronotype.Previous studies have found that circadian rhythm processes and homeostatic processes regulate chronotype(CS model),and the time of day(TOD)effect may include the role of both processes.Based on the time of day changes that may help to probe the mechanisms of chronotype.To deeply reveal the neural function of chronotype,the circadian rhythm mechanism and homeostasis mechanisms need further exploration.Therefore,the TOD effect,circadian rhythm mechanisms,and homeostasis mechanisms were examined in three experiments in Study 2.Compared with the morningness chronotype participants,the psychological behavior performance of eveningness participants are more impaired,and effective intervention is particularly necessary.Since the chronotype is modulated by the dual process of the CS(CS,C: circadian rhythm,S: homeostasis)model,experimental manipulation of each process separately may show better intervention effects.Study 3examined the intervention effects on the eveningness chronotype participants through the light intervention on the circadian rhythm process and the homeostatic sleep pressure intervention on the homeostatic processes.Study 1 first determined the accuracy and scope of application of the different chronotype measurement tools through experiment 1,and examined that the consistency of subjective and objective measurement was influenced by behavioral and environmental factors(including gender,age,sleep quality,insomnia severity and geographical location).On the basis of experiment 1,experiment 2 used independent component analysis to investigate the relationship between chronotype and resting state functional connectivity between large-scale brain networks,and revealed the neural mechanism of different chronotype.The results of experiment 1 found a significant correlation of chronotype measurement between the questionnaires and the actigraphy on 421 college student participants.Sleep quality was significantly correlated with chronotype,while the insomnia severity index was only associated with the questionnaire measure of chronotype(rMEQ,MSFsc).Stepwise regression models suggest that gender,sleep quality,and geographic location affect the consistency of the questionnaires and actigraphy measurement,with no effect on the insomnia severity index.Compared with other chronotype measurement tools,rMEQ may reflect relatively stable chronotype characteristics.Based on the conclusions of experiment 1,rMEQ measurement may be more suitable in the chronotype mechanism study of Experiment 2.In Experiment 2,56 morningness chronotype paricipants and 77 eveningness chronotype paticipants were selected,and resting-state fMRI data were collected from all subjects.The components of DMN and FPN were determined by independent component analysis,extracting the resting-state functional connectivity(FC)values after Fisher-z transformation of both networks,and subsequenty analyzing the correlation of FC and rMEQ scores.The results revealed a significant correlation between chronotype and DMN-FPN FC,but the morningness and eveningness chronotype participants have different onset sub-regions in the two networks.Morningness chronotype participants’ rMEQ scores were significantly positively correlated with left superior frontal gyrus-left inferior parietal gyrus functional connectivity,more prefer to the morningness chronotype with the stronger functional connectivity,which may reflect more the characteristics of the intrinsic circadian rhythm.The association between the eveningness chronotype and left angular-right middle frontal gyrus functional connectivity was negatively correlated,more biased to the eveningness chronotype with higher functional connectivity,which may be more sensitive to homeostatic processes.Study 2 mainly explored the neural mechanism of chronotype based on the CS model.The TOD includes the joint action of circadian rhythm and homeostatic processes.Experiment 3 explores the TOD mechanism of chronotype,examining the potential effects of the two processes.In experiment 3,196 college students were recruited,including 64 morningness chronotypes and 128 eveningness chronotype participants,all of which completed fMRI scans at random between 7:30 and 22:30.The same fMRI data processing method as in Experiment 2.ANOVA [2(chronotype: morningness /eveningness chronotype participants)*3(TOD: short/medium/long)] was used to test the difference in the resting state functional connectivity of DMN-ACN at different TOD conditions and found differences in DMN-ACN FC between morningness and eveningness chronotype particiapants at different arousal levels(TOD).With the prolonged of the TOD,the functional connectivity of DMN-ACN in the morningness chronotype participants(including right angular-right insular,left angular-right insular)decreases continuously.In contrast,the eveningness chronotype participants’ functional connectivity gradually increases after decreasing.Different chronotypes exhibit different functional connectivity patterns under the same homeostatic sleep pressure.The optimal linear fitting results appeared to have rhythmic fluctuations on morningness and eveningness chronotype participants’ DMN-ACN functional connectivity,suggesting that the effect of TOD may incorporate the role of both circadian rhythm and homeostatic processes.In experiment 4,55 college students were selected according to the rMEQ’ chronotype classification criteria,including 26 morningness and 29 eveningness chronotype participants.All participants were required to complete the tasks and collect resting-state fMRI data at the maximum sleep pressure,ie,the homeostatic process peak time and the daily sleep onset time.Circadian mechanisms of chronotype were examined using the same fMRI data analysis method as in Experiment 2.The results of independent sample t-test found that the DMN-FPN(right angular-right inferior parietal gyrus,left middle temporal gyrus-right inferior parietal gyrus,right angular-right middle frontal gyrus)functional connectivity of morningness chronotype participants is significantly greater than the eveningness chronotype,The functional connectivity of DMN-FPN is closely related to the sleep-wake pattern(Facer-Childs et al.,2019),the results may reflect more the characteristics of the intrinsic circadian rhythm.Experiment 5 screened 55 college students,including 26 morningness and 29 eveningness chronotype participants,and all participants completed various tasks and resting-state fMRI scans at the peak time of body temperature rhythm.The fMRI data processing was the same as in experiment 2,and the independent sample t-test found significant differences in DMN-FPN(left angular gyrus-right parietal inferior margin angular gyrus)functional connectivity between the two groups,which was lower in the eveningness chronotype participants.Decreased functional connectivity of DMN to other networks was associated with increased homeostatic sleep pressure(Tushaus et al.,2017),the results may reveal homeostatic mechanisms of morningness-eveningness chronotype participants.In addition,experiments 4 and 5 also found that the eveningness chronotype of cognitive task performance(3-back)and emotional experience(BDI)were worse.Experiments 6 and 7 of Study 3 intervened the eveningness chronotype participants based on two processes of the CS model.In experiment 6,30 eveningness chronotype participants were selected by rMEQ,and the subjects were required to complete overnight sleep monitoring and task assessments(pre-test)on the first day,90 minutes of blue light each morning and 90 minutes of red light each night for the next three days.On the fourth night,the whole night sleep monitoring was completed,and on the morning of the fifth day,the task evaluation was completed again(post-test).After red and blue light intervention,the results of paired sample t-test found that the eveningness chronotype participants’ cognitive task(Ospan)performance increased significantly,mood(PANAS,BAI,BDI)and sleep quality improved,and even changed the sleep structure(increased sleep duration,shorter sleep latency,decreased sleep disruption,increased sleep efficiency,and increased slow wave sleep duration and proportion).Increased sleep pressure after sleep restriction may modulate individual cognitive activity by regulating long-range potentiation and improve improved-behavioral performance after restorative sleep.Experiment 7 using rMEQ classification criteria to select 29 eveningness chronotype participants,requires the subjects to complete baseline overnight sleep monitoring and task assessment(pre-test)on the first day,the sum of the following three days of daytime nap(up to 30 minutes)and nighttime sleep(no more than 5.5 hours)is no more than 6 hours,and to ban coffee or energy drinks.On the fourth night,the whole night sleep monitoring was completed,and on the morning of the fifth day,the task evaluation was completed again(post-test).Similar to Experiment 6,the results of experiment 7 found that after the intervention to increase homeostatic sleep pressure,eveningness chronotype participants had less insomnia severity index,lower negative mood,improved cognitive task(Ospan)and vigilance task(PVT)performance,however,surprisingly lower positive mood(PANAS subdimension).In addition,sleep architecture also improved after the intervention,with increased sleep duration,shorter sleep latency,decreased wake and interruption duration during sleep,decreased N1 sleep duration and proportion,and increased N3 sleep and REM sleep duration and proportion.In conclusion,this study mainly focuses on the framework system of description-interpretation-intervention of the chronotype.The main contents include the measurement of chronotype,the neural mechanism of chronotype,and chronotype neural mechanism separation and chronotype intervention based on CS model.The main conclusions are as follows:(1)The subjective-objective measurement of chronotype is influenced by many factors(such as gender,sleep quality,and geographical location),among which,rMEQ is more suitable for the stable characteristics of chronotype,among which,rMEQ is more suitable for the stable characteristics of the chronotype.(2)Morningness chronotype and evening chronotype are strongly associated with DMN-FPN functional connectivity,and morningness chronotype with left superior frontal gyrus-left inferior parietal gyrus functional connectivity may mainly reflect the role of intrinsic circadian rhythm;the negative correlation of eveningness chronotype with left angular-right middle frontal gyrus functional connectivity may mainly express homeostasis process components.(3)The daytime effect mechanism of chronotype contains the influence of the circadian rhythm and homeostatic processes.The morningness and eveningness participants’ brain functional connectivity fluctuated rhythmically with time of day.With the increase of homeostatic sleep pressure,the functional connectivity of large-scale brain networks changed significantly,the left/right angular-right insular functional connectivity of the morningness chronotype decreased significantly,and the eveningness chronotype participants showed opposite changes in right angular-right insular functional connectivity.(4)The mechanisms of morningness and eveningness chronotype participants are differently regulated by circadian rhythm and homeostasis,the former is mainly manifested in the functional connectivity of the right angular-right inferior parietal gyrus,left middle temporal gyrus-right inferior parietal gyrus and right angular-right middle frontal gyrus,and the latter is mainly reflected in the left angular-right inferior parietal gyrus.(5)Compared with the morningness chronotype,the eveningness chronotype participants had worse cognitive performance and more serious emotional problems.After the intervention of light and homeostasis sleep pressure,the cognitive ability,emotional problems,sleep quality and sleep structure of the eveningness chronotype were significantly improved.