Circadian rhythms

Early in the course of circadian rhythm research, it became clear that individual animal subjects exhibit multiple rhythms whose peaks or troughs assume a fixed temporal relationship with each other, maintaining a state of internal synchrony. These observations motivated enquiry into what could be the nature of the system underlying such rhythms and inspired one of the pioneer circadian biologists, Colin Pittendrigh to develop the concept of circadian organization. Pittendrigh proposed that multiple oscillators constitute circadian timing systems, and each of themregulates a different rhythm. In this article, we will discuss what the evidence over the years suggests about the circadian organization and how our understanding of this system has matured.     

Circadian rhythms

Circadian (circa = about; dian = day) rhythms are amongst the most widely studied rhythmic behaviors across a wide range of organisms. Clocks driving circadian rhythms are termed circadian clocks and involve a network of functionally conserved genetic elements that mediate various oscillatory, physiological and behavioral phenomena and help tune the organism to remain in-sync with the external world. While some of the characteristic functional properties of circadian rhythms and clocks driving such rhythms have been studied for a long time now, our knowledge of the molecular and genetic architecture of circadian clocks remained elusive until recent years. This is the second article in a series on circadian rhythms and will introduce you to the molecular cogs and wheels of circadian clocks.     

Circadian rhythms

Over the series of articles on circadian rhythms, we saw that living organisms exhibit daily rhythms in multiple behaviours and physiological processes. Although some rhythms may be passive responses to 24 h environmental cycles, many are regulated by endogenous-rhythmgenerating machinery called circadian clocks. We have introduced the concept of circadian clocks, their organization and the underlying molecular mechanisms. In this article, we will dwell upon one of the most fundamental questions pertaining to circadian clocks, ‘Why do we have them?’. The aim of this article is not to provide answers, but to discuss the efforts and strategies used to address this question and critically evaluate explanations proposed till date.     

Circadian rhythms of tonic immobility in the rat: Evidence of an endogenous mechanism

Circadian rhythms of tonic immobility were found in male albino rats raised on a 12-h diurnal light cycle and tested at 6-h intervals. Durations of immobility were twice as long at 2000 h as at 1400 h. These differences persisted when rats were exposed to constant darkness for 10 days, but disappeared when rats were maintained in constant light for the same period. Since endogenous circadian rhythms of certain monoamine levels persist in constant darkness yet disappear under constant light, it is suggested that cycles of tonic immobility in rats are also endogenous. When the diurnal pattern of tonic immobility duration is compared to that of various neurohumors, immobility duration appears to parallel melatonin production and to be opposite in phase to the cycle of serotonin levels. Duration of immobility increased over trials, although the number of inductions required to produce immobility decreased. This suggests that instrumental conditioning may modify the immobility response to some extent.     

Circadian typology and style of thinking differences

The purpose of the present study aims to investigate the relationship between circadian typology and learning–thinking styles conceptualised as a preference toward information processing typical of the right vs. the left cerebral hemisphere. A sample of 1254 undergraduates (380 boys and 874 girls; mean age = 21.86 ± 2.37,) was administered the reduced version of the Morningness–Eveningness Questionnaire (r-MEQ), which detects three chronotypes (morning-, intermediate- or evening-types), and the Style Of Learning And Thinking (SOLAT) questionnaire, conceived as a tool to measure the tendency toward the right-, integrated-, and left thinking. A two-way ANOVA on SOLAT scores with circadian typology and gender, as between-subjects factor, and age as covariant, showed that morning-types scored higher in the left-thinking scale than intermediate- and evening-types, and that evening-types obtained significant higher scores for right-thinking style than intermediate- and morning-types. This circadian typology effect was also confirmed by multiple regression.     

Civic rhythms in an informal,media-rich learning program

Increasingly, adult mentors in informal, media-rich settings, like libraries and museums, seek to integrate both learning and civic engagement opportunities for youth into designed programming. This article illustrates how youth open and sustain opportunities for civic engagement over the course of a six-month, youth-driven program – Metro: Building Blocks (MBB) – housed within a digital media learning lab in an urban public library. Analysis develops the concept of civic rhythms as a means to feel out the social and affective contours of civic engagement that emerge in MBB. To better understand the civic rhythms of MBB, analysis focuses specifically on three rhythmic elements: pulsation, reciprocation, and oscillation. The article concludes suggesting that future research develop principles for designing-in-time that assist researchers and mentors in attuning to the youth-driven rhythms that sustain informal, media-rich programs.     

Circadian Rhythms in Cognitive Processes: Implications for School Learning

Circadian variations have been found in cognitive processes, such as attention, working memory, and executive functions, which may explain oscillations in the performance of many tasks. These cognitive processes improve during the day and decrease during the night and early hours of the morning. Sleep deprivation further decreases these cognitive processes during daytime hours. This review analyses the recent findings on circadian rhythms in cognitive processes, as well as the implications of these rhythms for school learning.     

The rhythms of pedagogy: an ethnographic study of parenting education practices

Educational research is increasingly turning to conceptual frameworks from a range of disciplines in order to enrich understandings of education, pedagogy and learning. This paper draws on the work of Henri Lefebvre, specifically rhythmanalysis, to explore the nature and the function of pedagogy. The context is an ethnographic study of parenting education and pedagogic practices in a child and family service in Sydney. Three features of rhythmanalysis are discussed: kinds of rhythm, rhythms and bodies, and oppositions such as repetition and difference, fast and slow and secret and public. Through these concepts, intricate connections between rhythm and pedagogy are identified, including rhythms as providing a pedagogic imperative, rhythms as content and mechanisms at the heart of pedagogy and rhythms as outcomes of learning. The paper argues that rhythmanalysis opens up possibilities for new questions, different kinds of empirical sensibilities and distinctive accounts of pedagogy and learning in continuing education.     

Immediations and rhythms of speculative design: Implications for value in design-based research

This paper presents data from the first six-months of an ongoing speculative design project in which youth and researchers co-created a videogame club, and later an eSports team, in an urban youth centre in Montréal, Québec. It describes how process philosophy informed researchers’ approach to speculative design, allowing youth and researchers to co-compose a sense of value for the club and the potentials for what they could do together through the club. This speculative process is contrasted with structuralist approaches to design-based research in education, which can overly or pre-determine value and mechanisms of social change, with or without the collaboration of youth and communities.     

对含蓄蕴藉的文外之美的张扬--论王士禛神韵诗的审美追求

王士镇的诗歌以“神韵”说为指导,强调言外之意,含蓄蕴藉,深得诗之本旨和艺术创造的真缔,并与清初变化了的社会心理合拍,受到皇权的关注和眷遇。其神韵诗追求文外之美,冲和淡远,风致清新,继承王、孟一派的家数,含情绵渺而纡徐曲折,惨淡经营却不露斧凿痕迹,音节流利跌宕,词句明隽圆润,令人回味遐想,把我国诗歌的传统精神和古典审美特征张扬到极致,在诗歌史上作出了贡献。     

Dissonance Between Parent‐Selected Bedtimes and Young Children's Circadian Physiology Influences Nighttime Settling Difficulties

Nighttime settling difficulties (i.e., bedtime resistance, sleep‐onset delay) occur in about 25% of young children and are associated with attentional, behavioral, and emotional problems. We examined whether the timing of internal (endogenous) circadian melatonin phase (i.e., dim light melatonin onset; DLMO) and its relationship with parent‐selected bedtimes were related to nighttime settling behaviors. Fourteen regularly napping preschoolers (8 females; 30–36 months) participated in a 6‐day protocol (parent‐report of nighttime settling, actigraphic assessment of sleep onset latency, evening salivary DLMO). Average DLMO clock time was 07:40 p.m. ± 00:48 minutes, occurring 29 minutes ± 32 minutes prior to bedtime (lights‐out). Children with later DLMOs had longer sleep‐onset latencies (r = .62) and poorer success in falling asleep (r = ?.59). Children whose bedtimes were closer to their DLMO had longer sleep‐onset latencies (r = .72) and increased bedtime resistance (r = ?.54). We conclude that dissonance between parent‐selected bedtimes and children's circadian physiology may contribute to the development of nighttime settling difficulties in early childhood.     

生理节律与体育类高考成绩的相关性的研究

通过剖析45名2002年体育高考学生的术科和化高考取得优异成绩时的生理节律，发现生理节律与高考成绩关系密切．学生处在高潮期时易于考出好成绩．体育术科高考成绩主要与体力钟、情绪钟密切相关；化课高考成绩主要与智力钟、情绪钟密切相关．