bluuebunny/crossref_metadata_2025 huggingface dataset:
Teaching College Composition with Computers
Authors: BERNHARDT STEPHEN A. , WOJAHN PATRICIA G. , EDWARDS PENNY R.
Published: March 2007

To understand the ways that teachers adapt writing instruction to a microcomputer classroom, the researchers observed and recorded activities minute-by-minute in four classes for a full semester of introductory composition. Two experienced teachers each taught two classes: one traditional class and one class that met for half of its time in a microcomputer classroom. This report contrasts their classes, calling attention to (a) the time pressures created by teaching with computers, (b) issues in training students to be proficient at word processing and revising, (c) ways a microcomputer classroom can foster workshop approaches to teaching writing, (d) the need for carefully structured classroom activities, and (e) the importance of teachers sharing with students common values for learning with computers in a group setting.
Interactive Written Discourse as an Emergent Register
Authors: FERRARA KATHLEEN , BRUNNER HANS , WHITTEMORE GREG
Published: March 2007

Text transmitted electronically through computer-mediated communication networks is an increasingly available yet little documented form of written communication. This article examines the syntactic and stylistic features of an emergent phenomenon called Interactive Written Discourse (IWD) and finds that the concept of “register,” a language variety according to use, helps account for the syntactic reductions and omissions that characterize this historical juxtaposition of text format with real-time and interactive pressures. Similarities with another written register showing surface brevity, the note taking register, are explored. The study is an empirical examination of written communication from a single discourse community, on a single topic, with a single recipient, involving 23 experienced computer users making travel plans with the same travel advisor by exchanging messages through linked computers. The study shows rates of omissions of subject pronouns, copulas, and articles and suggests that IWD is a hybrid, showing features of both spoken and written language. In tracing variable use of conventions such as sentence initial lower case and parentheses, the study shows that norms are gradually emerging. This form of written communication demands study because, as capabilities expand, norms associated with this medium of communication may come to influence or even replace those of more traditional writing styles.
Bilingual Minorities and Language Issues in Writing
Authors: VALDÉS GUADALUPE
Published: March 2007

This article takes the position that teaching writing effectively to diverse students of non-English background will require an examination of existing views about the nature of writing and a critical evaluation of the profession's ability to work with bilingual individuals of different types. In order to explain this view, the article is divided into three parts. Part 1 describes the nature of bilingualism, identifies the population of students who can be classified as American bilingual minorities, and suggests that existing compartmentalization within the composition profession cannot address the needs of this particular population. Part 2 of the article reviews trends in current scholarship in second-language writing and points out that most of this research has focused on ESL students rather than on fluent/functional bilinguals. Finally, Part 3 lists and discusses a number of research directions in which the involvement and participation of mainstream scholars would be most valuable. In presenting an outline of questions and issues fundamental to developing effective pedagogical approaches for teaching writing to bilingual minority students, this final section argues that involvement in research on non-English-background populations of researchers who generally concentrate on mainstream issues would do much to break down the compartmentalization now existing within the English composition profession. It further argues that by using bilingual individuals to study questions of major theoretical interest, the profession will strengthen the explanatory power of existing theories about the process and practice of writing in general.
Students' Strategies for Writing Instructions
Authors: DONIN JANET , BRACEWELL ROBERT J. , FREDERIKSEN CARL H. , DILLINGER MIKE
Published: March 2007

A“cognitive discourse analysis” was employed to analyze instructions for using a word processor written by eighth-grade students. The approach analyzes text structure in order to specify underlying semantic and conceptual knowledge structures. Our analyses revealed that the written instructions produced by the student writers were deficient in providing a reader with the information necessary for performing the task in two distinct ways. First, the group of students as a whole presented insufficient content information in their texts, particularly with respect to the subprocedures required to use the word processor. Second, the organization of students' texts did not parallel the hierarchical structure of the procedures described. These results suggest the importance of looking at writing from the point of view of the knowledge structures being expressed.
Records as Genre
Authors: SCHRYER CATHERINE F.
Published: March 2007

This study reworks the concept of genre from rhetorical, dialectical, and dialogic perspectives. From these perspectives, genre is redefined as a stabilized-for-now or stabilized-enough site of social and ideological action. This definition is then applied to a specific literacy practice—medical record keeping—evolving in a specific context—a veterinary college. Data were gathered during a 6-month ethnographic study of the college. The larger research project focused on the teaching and learning practices that constituted literacy, i.e., the ways of speaking, reading, writing, and listening characteristics of veterinary medicine. The project consisted of interviews, observation, and document collection. Triangulation was achieved both within and between methods. Data were analyzed using Glaser and Strauss's “grounded theory” techniques. When the concept of genre is applied to medical record keeping, the complexity of this literacy practice becomes apparent. A specific record-keeping system—the Problem Oriented Veterinary Medical Record (POVMR) system—was the site of intense controversy at the college. The system articulated a set of values that one group of faculty and clinicians espoused and another group rejected. The system itself was embedded in the exam structure of the college, and a good deal of evidence emerged that the POVMR itself was promoting certain types of literacy abilities and making others less likely.
Learning to Read Biology
Authors: HAAS CHRISTINA
Published: March 2007

This longitudinal study examines the reading processes and practices of one college student, Eliza, through eight semesters of undergraduate postsecondary education. Specifically, the study traces the development of this student's beliefs about literate activity—focusing not only on changes in her reading and writing activities per se, but also on her views about those activities, her representations of the nature of texts, and her understanding of the relationship between knowledge and written discourse within her disciplinary field of biology. Multiple data sources—including extended interviews, reading/writing logs, observations and field notes, texts, and read-and-think-aloud protocols—were used to explore Eliza's rhetorical development over her 4 college years. Results of various analyses together suggest that Eliza's conceptions of the function of texts and the role of authors—both as authors and as scientists—grew in complexity. A number of possibly interrelated factors may account for Eliza's expanding notions of authors and of texts: increased subject matter knowledge, instructional support, “natural” development, and mentoring in an internship situation.
The Emergence of Genres
Authors: CHAPMAN MARILYN L.
Published: March 2007

This article examines the writing and drawing produced by a group of children during “writing workshop” time throughout their first-grade year. The purpose of the study was to obtain insight into the general question: Do genres “emerge” in ways analogous to other aspects of writing development? While the study is limited to a specific group of first-grade writers, it provides insights which suggest that genre may indeed be “emergent.” Emergence is supported by evidence of the following: Quantitative and qualitative changes in the organization of texts, with genres appearing as adaptations rather than fixed forms or generalized verbal products; an interplay among drawing, talking, reading, and writing in the construction of genres; the influence of the specific recurring social context of Writing Workshop and the genres surrounding and embedded in it; and the impact overall of the socialization into literacy occurring within this specific classroom community.
Context and Rhetorical Reading Strategies
Authors: HASWELL RICHARD H. , BRIGGS TERRI L. , FAY JENNIFER A. , GILLEN NORMAN K. , HARRILL ROB , SHUPALA ANDREW M. , TREVINO SYLVIA S.
Published: March 2007

The authors twice replicated C. Haas and L. Flower's 1988 think-aloud reading study, which found that graduate students used “rhetorical” reading strategies to interpret a passage, whereas first-year college students used such strategies hardly at all. Rhetorical reading strategies use suppositions about the social, cultural, and historical context of the writing. The main intent of the replications was to see whether different outcomes might be found if the passage read dealt with a topic more familiar to first-year students. With the original passage, the results roughly supported Haas and Flower. But with the more familiar topic, the undergraduates generated substantially more rhetorical comments than they did with the Haas and Flower passage. Personal narrative and value-laden commentary were also measured, with older students far outproducing first-year students. The caution for researchers and teachers is to avoid hasty assumptions about underlying language competence without considering contextual factors.
Motivational Orientations of Adult Education Participants: a Factor Analytic Exploration of Houle's Typology
Authors: Boshier Roger
Published: March 2007

To test Houle's typology of "motivational orientation" in a New Zealand context, and to develop a factor analytically based mea sure of motive for attendance, 233 adult education participants selected at random from three institutions completed a 48 item Education Participation Scale. A factor analysis and promax/ varimax rotation yielded 14 first-order factors which were subse quently intercorrelated, factor analysed and rotated to yield second and then third-order factors. The meaning of the resultant factors is discussed. In developing a model of adult education participa tion, it is proposed that participants are basically "being" or "deficiency" motivated. The concept of homeo and heterostasis is discussed. Education Participation Scale factors purporting to measure these different types of motivation are identified. Partici pation is shown to stem from motives moie complex than those originally identified by Houle.
The Relationship Between Dogmatism Scores and Performance Ratings Among Adult Educators
Authors: Funk C. Dennis , Carter G.L.
Published: March 2007

As a part of a larger research undertaking concerned with identify ing variables which contribute to high performance among adult educators, particularly Extension personnel, this study was ad dressed to an examination of the relationship between dogmatism (open-closed-mindedness) and job performance. Data were col lected by mail questionnaires from 486 out of 503 (96.6%) county Extension workers with major responsibility for adult education programs in agriculture in five states. Dogmatism was measured by the Rokeach Dogmatism Scale (Form E) included in the ques tionnaire. Performance was determined by supervisor ratings using the paired comparison technique.

The data revealed a slight negative relationship (gamma = -.19) between dogmatism and performance. This relationship was affected by the age and level of education of the respondents. Open-minded agents tended to be rated higher in performance than the close-minded.
The Effectiveness of Taped Reading Instruction in Increasing the Reading Rate and Comprehension of Undereducated Adults
Authors: Bryant Antusa S. , Bryant Benjamin F. , Christiansen Dagny , Fischer Lucille
Published: March 2007

This study analyzed reading rates and reading comprehension as they relate to two methods of reading: 1) silent and 2) aural- silent using a tape recorder. Adults (N = 100) who were either grade school or high school dropouts were administered two com parable selections from which to read and to answer questions. From one selection, Ss read silently; and from the second, they read silently as they listened to the selection recorded at approxi mately 127 wpm. When the two methods were compared, taped instruction resulted in statistically significant (p < .05) improve ment of both speed and comprehension. However, there were indications that 127 wpm was too slow for Ss reading above the 8th grade level and resulted in dysfunction in both rate and com prehension.
Adult Education in the People's Republic of China
Authors: Lucas Christopher J.
Published: March 2007

Adult education in China today is utilized as an instrument for the consolidation and perpetuation of the Communist social revolu tion. Pursuant to the fundamental ideological, political, and eco nomic objectives of the Chinese government, considerable experi mentation is underway to devise more adaptive teaching-learning modes for adults. The major thrust is to create a largely informal, non-schooled, and de-centralized educational system coordinated with, but not necessarily dependent upon, formal institutionalized schools. Significant progress has been made in adapting curricula and instruction to the unique needs of mature learners with respect to fostering literacy, teaching occupational skills, and inculcating prevailing social norms. Further study is required to ascertain the possible applicability elsewhere of these recent Chinese educational innovations.
The Common Concern: Controlling the Professionalization of Adult Education
Authors: Wilson Arthur L.
Published: March 2007

Using the findings from a study of the adult education handbooks, the purpose of this paper is to present an argument that university researchers in the field of adult education have relied upon a natural science model of empirical analysis to develop the knowledge base of adult education in order to control the development of the field as a profession. This professsionalization process depends upon using scientifically-derived knowledge to standardize professional practice and the training of practitioners in order to develop a market share in a service economy.
Gay Discourse In Adult Education: A Critical Review
Authors: Hill Robert J.
Published: March 2007

This paper explores the dual roles, both emancipatory and oppressive, that adult education plays within the gay and lesbian community. The paper argues that heterosexism, a widely shared system that assumes compulsory heterosexuality for everyone, results in domination of lesbian and gay people. Theoretically, the paper locates heterocentricity within the larger field of education. An extensive literature review is used to demonstrate that mainstream adult education reproduces heterocentric assumptions, social relations, and beliefs, at the expense of gay resistance discourse. Libratory, popular adult education within the gay and lesbian community is contrasted with more mainstream adult education practices, purposes, and programs.
Neither Polemical nor Visionary: Language, Professionalization, and the Representation of Women in the Journals of Adult Education, 1929-1960
Authors: Thompson Melody M. , Schied Fred M.
Published: March 2007

Using Critical Language Study as the method of analysis, this paper explores the ways in which (a) the language used in early adult education journals to structure the professionalizing field mirrored and perpetuated hierarchical gender relationships of the larger society, and (b) descriptive and prescriptive leadership discourse made it difficult for readers to view women as leaders or potential leaders of the field. We argue that androcentric linguistic conventions limited the visibility of women as leaders and that the use of exclusionary language intensified as the field became more aware of and responsive to its marginality in relation to the larger educational field. Finally, we suggest an incompatibility between the field's changing values and an acceptance of women as leaders, and further suggest that this incompatibility may have contributed to the invisibility of women as leaders in histories of adult education.
Learning, Culture, and Learning Culture
Authors: Jacobson Wayne
Published: March 2007

Though adults have long faced the experience of learning to function in new cultural contexts, very little is understood about the processes of this sort of learning. This paper approaches learning culture from the position that cultural knowledge is best understood in terms of situated cognition. Contexts do not simply provide useful information in support of thinking and learning, but are inseparable from cognitive processes. Viewing culture in this way carries specific implications for understanding how a new culture is learned and how it might be taught. In particular, processes of learning culture can be seen to parallel processes of gaining practitioner knowledge, while processes of teaching culture can be modeled on the notion of cognitive apprenticeship.
Observing Other Teachers Teach: The Effect on Adolescent Teaching Behavior
Authors: Bloch Marianne N.
Published: March 2007

Low-income adolescents were instructed to observe videotapes of two teachers consistently modeling effective teaching of young children in a structured teaching task. Simultaneously the subjects incidentally observed systematic differences in the inquiry- and directive-oriented teaching styles and novel behavior being modeled. As a result of observation, the subjects imitated aspects of the incidentally observed inquiry teaching style modeled as well as important aspects of the effective teaching behavior they were instructed to observe. Factors affecting subjects' selective imitation of the two models' styles were examined. The most significant factors examined were subjects' perceptions of their own teaching style and their perceptions of the teaching models' effectiveness.
Relations between Sexual Attitudes, Gender, and Sexual Behaviour Concepts of Older Adolescents
Authors: Gfellner Barbara M.
Published: March 2007

A cognitive developmental model of sexual behaviour understanding was used to evaluate sexual attitudes in relation to sexuality development. Relations were established between sexual concept development and sexual attitudes among older adolescents. Gender differences were supported in sexual concept development and sexual attitudes and a differential alignment was found for sexual concepts and gender in relation to sexual attitudes. The multidimensionality of sexual attitudes was supported and results suggested the utility of differentiating General Permissiveness from Premarital Permissiveness in the study of sexual attitudes and adolescent sexuality development.
A Model of Parenting Style, Adolescent Individuation and Adolescent Self-Esteem
Authors: Bartle Suzanne E. , Anderson Stephen A. , Sabatelli Ronald M.
Published: March 2007

A hierarchical model of adolescent personal adjustment is presented, which suggests that family system-level relationships affect individuation levels of off-spring, which in turn affect personal adjustment. This model was tested using perceived parenting style as the first tier variable, ani inidicator of individluation as the second tier variable, and self-esteem as an indicator of personal adjustment. Results gave limited support to the model using this sample of adolescent males and females. Interesting differences were noted itn tile intdividuation process for males and females and the differential effects of mothers' and fathers'parenting style. It was emphasized that future research in t/zis area should more carefully examine the inter-dependence between sex of the child, the parenting style of each parent, and adolescenit inidividuation when examininig the mediators of adolescent development and adaptation.
Gender-Role Orientation of Adolescent Females
Authors: Mullis Ronald L. , McKinley Kathleen
Published: March 2007

The purpose of this study was to examine the effects of gender-role orientation on self-esteem and locus of control of female adolescents. A total of 87 junior high school females and 48 senior high school females completed the Bem Sex-Role Inventory, the Texas Social Behavior Inventory, and the Nowicki-Strickland Locus of Control Scale for Children. Gender-role orientation was related to self-esteem but not to locus of control. Adolescents classified as androgynous or masculine had higher self-esteem than adolescents classified as feminine and undifferentiated. Differentialpatterns of gender-role orientation effects were found for junior high school females when compared to senior high school females. Implications of these findings and directions for future research are discussed.
The Development of a Stress Response Scale for Adolescents
Authors: Curtis Steven , Adams Gerald R.
Published: March 2007

A Stress Response ScaleforAdolescents (SRSA) was developed to measure self-perceived stress responses of adolescents between 14 and 21 years of age. Study 1 involved item selection, scale construction, item reduction, and estimations of reliability and validity. Study 2 tested the ability of the scale, through role enactment methodology, to distinguish differences in stress responses between those in a high stress versus low stress condition. Study 3, used role enactment methodology to test the potential for the scale to detect changes in stress response levels when individuals were taken from a low to high or a high to low stress condition. Finally, Study 4 assessed individual differences in stress responses in a test anxiety context. Thefinal version of this instrument includes 19 stress response items. Thefour studies suggest promiseforfurther development of a self-report stress response scale.
Friendship Characteristics of Adolescents Referred for Psychiatric Treatment
Authors: Claes Michel
Published: March 2007

This study was carried out with 256 adolescents: 56 subjects referred to adolescent psychiatric outpatient clinics and a control group of 209 adolescents from two public high schools in Montreal. Subjects were divided into two age groups: 12 through 14-year-olds and 15 through 17-year-olds. A questionnaire examining the various characteristics ofthefriendship networkand the affective nature offriendships was given to all subjects. The basic hypotheses that guided the present study are confirmedfor the older referred subjects. We notice that in comparison to the control group in high school, the group of referred adolescents between the ages of 15 and 17 years possesses a more restrictedfriendship network Their relationships are poorer in terms of attachment with close friends and are marked more often by conflictual experiences. The severity of diagnosis is comparable between age groups but the older adolescents have an older psychiatric history. A hypothesis of deterioration offriendship relations was proposed for the referred subjects. The results obtained support a model that suggests that problems in friendship relations and the deterioration of these relations in the course of adolescence constitutes, among other symptoms, the expression of more fundamental psychological difficulties that have driven the referred adolescents to a psychiatric outpatient clinic.
Communities as Contexts for Adolescent Development
Authors: Blyth Dale A. , Leffert Nancy
Published: March 2007

Research on the relation between context and adolescent development has been driven by an awareness of increases in problem behaviors during adokscence and an interest in the role of contextualfactors that may affect adolescent outcomes. The present study focused on cross-sectional views of changes in youths over time and compared 12 different conmnunities as experienced by 9th through 12th graders, using the community as the main unit of analysis. The analyses demonstrated that very different percentages of youths in different types of community experience community strengths. In addition, similar types of youths (i.e., vulnerable, average, and high-asset youths) are affected differentially by the overall health of the community. In particular, vulnerable youths, those with few personal assets, benefit from living in healthier communities and these effects are visible across all types of communities. Analyses also revealed grade differences among different types of youths.
Autonomy, Relatedness, and Male Adolescent Delinquency
Authors: Kuperminc Gabriel P. , Allen Joseph P. , Arthur Michael W.
Published: March 2007

This study explored adolescents'developmental strivings for autonomy and relatedness as motivations in socialproblem-solving competence, and the relevance of those strivings to explaining variation in delinquent activity. Eighty African American and Caucasian male adolescents (11 through 18 years of age) at high riskfor delinquency provided their likely strategies for resolving hypothetical interpersonal dilemmas. Strategies reflecting relatedness striving and autonomous-related reasoning were correlated positively with social problem solving and academic competence. Acts of delinquency were more frequent among adolescents whose strategies showed little relatedness striving, combined with lackof understanding that relationships can support bothautonomy and relatedness. These findings support the view that motivations to establish autonomy while maintaining relationships characterize important dimensions of adolescent social competence and may help enhance knowledge of adolescent problem behaviors. Recommendations for prevention and intervention efforts include increased attention to providing settings that facilitate positive expressions of developmental needs for autonomy and relatedness.
Dimensions of Religiosity as Mediators of the Relations Between Parenting and Adolescent Deviant Behavior
Authors: Litchfield Allen W. , Thomas Darwin L. , Li Bing Dao
Published: March 2007

Data from over 1,500 American adolescents-collected in two separate projects, both longitudinal-were used to examine the interrelations among three dimensions of adolescent religiosity and the degree to which those mediated the effects of parental behavior on adolescent deviant outcomes. The findings lend support to this special issue theme that various dimensions of parent/child interaction have independent effects on adolescent characteristics (religiosity and deviance). Generally, the three religiosity dimensions functioned as intervening variables between parental behaviors and deviance, with adolescents' expectations of future religious activity reducing subsequent deviance more than either public or private adolescent religiosity. The patterns of findings imply that out ofparent/child relationships and theirpublic andprivate religious activity, adolescents construct a view of what will be theirfuture patterns of religious activity. They then tend to participate or not in deviant behavior consonant with their future religious orientation.
Structural Equation Modeling of Group Differences in CES-D Ratings of Native Hawaiian and Non-Hawaiian High School Students
Authors: Mcardle John J. , Johnson Ronald C. , Hishinuma Earl S. , Miyamoto Robin H. , Andrade Naleen N.
Published: March 2007

This report uses different forms of latent variable structural equation models (SEMs) of group differences in self-reported Center for Epidemiologic Studies Depression (CES-D) inventory results among a sample of Hawaiian and non-Hawaiian high school students.The models examined are organized progressively by increasing complexity, including mean differences models in the ANOVA tradition, mean differences combined with path analysis models, extensions to confirmatory factor analysis models, and common factor differences in multiple group models.Within each type of analysis, SEMs are defined and fitted to real CES-D data, and broad issues of group differences and invariance are considered.The substantive results indicate a high degree of invariance between Hawaiian and non-Hawaiian students within the same high schools on self-ratings of depression from the CES-D scale.These analyses illustrate theoretical and practical issues about common features and relationships among standard analysis of variance approaches and contemporary structural equation methodology.
Adolescent Social Initiative
Authors: Barber Brian K. , Erickson Lance D.
Published: March 2007

This article reports on an investigation of adolescent social initiative, a particular form of adolescent social competence. Specifically, the study explored the extent to which variations in this form of social competence can be understood as a function of the history of interpersonal relationships in the lives of adolescents. The sample (N = 750) consisted of two age cohorts (ages 11-13 and 14-17) that were assessed annually for 3 consecutive years (1995-1997) by way of a mailed self-report survey. Findings indicated that positive aspects of the parent-adolescent relationship (support, behavioral control) measured 2 years previous predicted adolescent social initiative directly or indirectly through the quality of interpersonal relationship with best friend, school officials, and community adults measured 1 year previous to the assessment of social initiative and/or through adolescent individual characteristics (self-esteem, antisocial behavior) measured concomitantly with social initiative. Although significant variance in the change in social initiative across the 3-year period was accounted for in both cohorts, a larger set of predictors was associated with social initiative among the younger cohort, suggesting that the social identity of younger adolescents was still dependent on their recent experiences in a variety of social relationships, whereas the parental relationship was the primary predictor for the older cohort.
The Long Branch of Phase-Environment Fit
Authors: Obeidallah Dawn A. , Hauser Stuart T. , Jacobson Alan M.
Published: March 2007

Based on the stage-environment fit perspective (Eccles & Midgley), we hypothesized that diabetic adolescents who experience a developmental match would be more likely to experience optimal psychosocial outcomes. Three questions were addressed: Are there links between developmental match and adolescents’psychosocial outcomes, and if so, do such links differ by diabetic status? What are the long-term implications for later psychosocial outcomes of developmental match, and do such links differ by diabetic status? Do adolescents differentially perceive community support as a function of their developmental match and diabetic status? We assessed diabetic and nondiabetic adolescent boys and girls from a larger longitudinal study of chronic illness. Family characteristics were observed in a revealed difference task. Results suggested that even after controlling for psychosocial factors during adolescence, the benefits of developmental match (and the costs of developmental mismatch) could be observed during young adulthood. In addition, preadolescents with diabetes perceived their community as more supportive than any other group of adolescents. Results are discussed within a developmental contextual perspective, with particular attention to the experiences of diabetic adolescents.
Sleep Initiation and Initial Sleep Intensity: Interactions of Homeostatic and Circadian Mechanisms
Authors: Borbély Alexander A. , Achermann Peter , Trachsel Lorenz , Tobler Irene
Published: March 2007

Sleep initiation and sleep intensity in humans show a dissimilar time course. The propensity of sleep initiation (PSI), as measured by the multiple sleep latency test, remains at a relatively constant level throughout the habitual period of waking or exhibits a midafternoon peak. When waking is extended into the sleep period, PSI rises rapidly within a few hours. In contrast, sleep intensity, as measured by electroencephalographic slow-wave activity during naps, shows a gradual increase during the period of habitual waking. In the two-process model of sleep regulation, it corresponds to the rising limb of the homeostatic Process S. We propose that PSI is determined by the difference between Process S and the threshold H defining sleep onset, which is modulated by the circadian process C. In contrast to a previous version of the model, the parameters of H (amplitude, phase, skewness) differ from those of threshold L, which defines sleep termination. The present model is able to simulate the time course of PSI under baseline conditions as well as following recovery sleep after extended sleep deprivation. The simulations suggest that during the regular period of waking, a circadian process coun teracts the increasing sleep propensity induced by a homeostatic process. Data obtained in the rat indicate that during the circadian period of predominant waking, a circadian process prevents a major intrusion of sleep.
Effect of Melatonin Infusion Duration and Frequency on Gonad, Lipid, and Body Mass in Pinealectomized Male Siberian Hamsters1
Authors: Elliott Jeffrey A. , Bartness Timothy J. , Goldman Bruce D.
Published: March 2007

The goal of this study was to discriminate between two hypotheses regarding how the circadian rhythm of pineal melatonin (MEL) production transmits photoperiodic informa tion : (1) A circadian rhythm of sensitivity to MEL regulates the hormone's effect; (2) the duration of the MEL signal, rather than its circadian timing, is the critical parameter of the MEL rhythm. The experiment examined the response of pinealectomized (PINX) male Sibe rian hamsters to 10-hr (short-day-type) versus 6-hr (long-day-type) duration MEL infusions (10 ng/infusion) in cycles with period lengths (T) of 18, 24, 36, and 48 hr. After cannula implantation, animals were moved from LD 16:8 to LD 10:14 (lights-on from 0500 to 1500 hr, EST), where the timed infusions began. Additional T 24 cycles included as controls employed 18-hr MEL, 18-hr saline (SAL), and 10-hr SAL infusions. Body weight and food intake were measured weekly. After 6 weeks, animals were killed; blood samples were taken for radio immunoassay (RIA) of serum follicle-stimulating hormone (FSH) and prolactin (PRL); and terminal body, epididymal white adipose tissue (EPIWAT), and paired testis weights were recorded. Six-hour MEL infusions failed to induce short-day-type effects, regardless of the period (T) of the infusion cycle. In contrast, compared to SAL and 6-hr MEL infusions, 10-hr MEL resulted in decreases in body, EPIWAT, and testis weights in T 24, but not in T 36 or T 48. In T 18, testis, body, and EPIWAT mass were decreased, but not to the same extent as in T 24. Similarly, daily 18-hr MEL infusions (T 24) were less effective as a short-day stimulus than were 10-hr MEL infusions. The effectiveness of 10-hr, but not 6-hr, MEL infusions in T 18 and T 24 is consistent with the duration hypothesis and argues against the circadian hypothesis. Neither hypothesis could have predicted that all infusion cycles of T ≥ 36 hr, regardless of the infusion durations, would fail to elicit short-day-type responses. This out come suggests a need for relatively frequent (T < 36 hr) MEL stimulation in addition to the requirement for adequate duration of each MEL infusion.
Relationship between Phase Resetting and the Free-Running Period in Djungarian Hamsters
Authors: Puchalski Wolfgang , Lynch G. Robert
Published: March 2007

A data set of 293 phase shifts was analyzed in order to determine the relationship between phase resetting and the free-running period (τ) in Djungarian hamsters. Phase shifts in response to a 15-min light pulse were assigned to one of two groups (τshot, <24 hr; τ long, >24 hr), and two phase response curves (PRCs) were constructed. The two PRCs differed predominantly in the advance region, which extended so far into the subjective day of PRClong that a dead zone was lacking. The functional significance of PRC differences was assessed by computer simulations of entrainment to varying skeleton photoperiods and entrainment to a 12-hr skeleton photoperiod with varying τ's. Results from these simulations confirmed the theoretical predictions by Pittendrigh and Daan: Stability of entrainment under varying photoperiods depended on the ratio of the PRC slopes at the phases illuminated by light (SE/S M). This ratio was always larger than 1 for PRClong. It approached 0 for PRCshort as soon as the evening light illuminated the dead zone; this occurred for entrainment to very short photoperiods. Stability of entrainment to lights-off was in general better for PRClong than for PRCshort, especially if PRClong was used in combination with τlong This suggests that it can be advantageous for stability of entrainment to lights-off to express a τ > 24 hr in combination with a PRC lacking a dead zone. Stability of entrainment under varying τ's was not much different for PRClong or PRC short. However, stability of entrainment deteriorated for PRC long in combination with short τ's, whereas it deteriorated for PRCshort in combination with long τ's.
The Effects of Temperature on the Circadian Rhythms of Flashing and Glow in Gonyaulax polyedra: Are the Two Rhythms Controlled by Two Oscillators?
Authors: Von der Heyde Frank , Wilkens Andreas , Rensing Ludger
Published: March 2007

Circadian rhythms of flashing and glow were recorded simultaneously in Gonyaulax polyedra by determining maximum and minimum light emission at each measured interval of 28 sec. In constant light, the two rhythms in some cases showed different period lengths (τ), the glow rhythm being up to 1 hr shorter than the flashing rhythm. Lower temperatures shortened the τ of the glow rhythm more than that of the flashing rhythm. The amplitude of the flashing rhythm decreased when the temperature was increased from 15°C to 25°C, whereas that of the glow rhythm was increased. These results may indicate that the two rhythms are controlled by two separate oscillators.
Entrainability of Circadian Activity of the Mosquito Culex pipiens pallens to 24-Hr Temperature Cycles, with Special Reference to Involvement of Multiple Oscillators
Authors: Chiba Y. , Uki M. , Kawasaki Y. , Matsumoto A. , Tomioka K.
Published: March 2007

Entrainability of the circadian rhythm of mosquito flight and locomotor activity was investigated by giving a 24-hr temperature cycle (28°C for 16 hr, 23°C for 8 hr) to the free-running rhythm or by shifting the temperature cycle. The phase angle difference between the entrained rhythm and the temperature cycle depended on the free-running period, but not on the circadian phase at which the temperature cycle started. The rhythm transients (advancing or delaying) to entrainment depended on phase, but did not depend on either the phase or the free-running period for their average speed. We postulate that flight and locomotor activity in the mosquito may be controlled by two circadian oscillators moving in different directions in response to the temperature cycle. It is likely that at least one of the oscillators is diphasic.
Light-Induced Phase Shifts in tau Mutant Hamsters
Authors: Shimomura Kazuhiro , Menaker Michael
Published: March 2007

Phase shifts produced by single 1-hr light pulses were compared in homozygous tau mutant and wild-type hamsters after several different kinds of pretreatment regimens. There was a dramatic increase in the magnitude of phase delays in the mutant hamsters as they were kept for progressively longer times in constant darkness (DD), and a smaller increase in the magnitude of phase advances. Under the same conditions a small increase in the magnitude of phase delays and no significant increase in phase advances occurred in the wild-type hamsters. After only 7 days in DD the phase response curves (PRCs) of mutant and wild-type hamsters were both type 1 and were indistinguishable from each other, whereas after 49 days in DD the PRCs of mutant hamsters had become type 0. Mutant hamsters were entrained to eight different T-cycles (1 hr of light per cycle), released into DD, and given a phase delaying light pulse 7 days later. T-cycles which entrained the animals so that the 1 hr of light fell between 6 and 9 hours after the onset of activity suppressed the amplitude of phase delays, whereas T-cycles which entrained the animals so that the 1 hr of light fell at other times did not suppress phase delays. The implications of the data for entrainment theory and the mechanism of action of the tau gene are discussed.
Naps as Integral Parts of the Wake Time within the Human Sleep-Wake Cycle
Authors: Aschoff Jürgen
Published: March 2007

Thirteen subjects lived singly in an isolation unit without temporal cues for an average time span of 32 days. They signaled the times when they woke up, took a meal, and retired, noting in their diaries what kind of sleep (nap or main sleep) they were going to have. In five subjects the free- running circadian rhythms remained internally synchronized. The other eight subjects became internally desynchronized, with different periods in the sleep-wake cycle and in the rhythm of body temperature, or developed a "circa-bi-dian" rhythmicity (i.e., a state of the circadian system in which the temperature rhythm regains synchrony with the sleep-wake cycle in a 2:1 ratio). The duration of naps was positively correlated with the duration of wake time (after subtraction of the nap), as well as with the duration of wakefulness preceding the nap. In contrast, the duration of main sleep was negatively correlated with the preceding wake time. It is concluded that naps are integral parts of the wake time, and that they follow the rules known from intermeal intervals and the perception of long time intervals such as 1 hr.
Light Treatment for Sleep Disorders: Consensus Report
Authors: Eastman Charmane I. , Boulos Ziad , Terman Michael , Campbell Scott S. , Dijk Derk-Jan , Lewy Alfred J.
Published: March 2007

The unhealthy symptoms and many deleterious consequences of shift work can be explained by a mismatch between the work-sleep schedule and the internal circadian rhythms. This mismatch occurs because the 24-h zeitgebers, such as the natural light-dark cycle, keep the circadian rhythms from phase shifting to align with the night-work, day-sleep schedule. This is a review of studies in which the sleep schedule is shifted several hours, as in shift work, and bright light is used to try to phase shift circadian rhythms. Phase shifts can be produced in laboratory studies, when subjects are kept indoors, and faster phase shifting occurs with appropriately timed bright light than with ordinary indoor (dim) light. Bright light field studies, in which subjects live at home, show that the use of artificial nocturnal bright light combined with enforced daytime dark (sleep) periods can phase shift circadian rhythms despite exposure to the conflicting 24-h zeitgebers. So far, the only studies on the use of bright light for real shift workers have been conducted at National Aeronautics and Space Administration (NASA). In general, the bright light studies support the idea that the control of light and dark can be used to overcome many of the problems of shift work. However, despite ongoing practical applications (such as at NASA), much basic research is still needed.
Twelve-Hour Phase Shifts of Hamster Circadian Rhythms Elicited by Voluntary Wheel Running
Authors: Gannon Robert L. , Rea Michael A.
Published: March 2007

Running in a novel wheel can serve as a nonphotic zeitgeber to entrain or phase shift circadian rhythms in hamsters. In this study, hamsters were entrained to a light:dark schedule of 14:10 h but had no access to running wheels. At four different phase points of the light cycle, hamsters were transferred to constant darkness and provided with running wheels. All hamsters began running shortly after transfer and were allowed to continue running at their own volition. Approximately 20% of the hamsters transferred at zeitgeber time (ZT) 23 (ZT 12 = lights out) ran more than 4 h after transfer and showed phase advances of the circadian activity rhythm by as much as 15 h, while hamsters that ran less than 4 h on average did not phase shift. A similar result was observed for hamsters transferred at ZT 2. Hamsters transferred at ZT 5 and 8 also did not phase shift if they ran less than 4 h, although the relation between longer runs and phase shifts became less evident. A sustained run in excess of 4 h appeared to be associated with large phase advances. These results show that under certain conditions, a single sustained bout of wheel-running activity is capable of phase shifting the circadian pacemaker by more than 12 h.
Synchronization of Circadian Rhythms of House Sparrows by Oral Melatonin: Effects of Changing Period
Authors: Heigl Sabine , Gwinner Eberhard
Published: March 2007

House sparrows (Passer domesticus) whose circadian rhythms of locomotor activity and feeding had been abolished by pinealectomy were held in constant dim light and periodically exposed to melatonin in the drinking water. By alternating 8 h of melatonin water with variable phases of tap water, rhythms with periods (T) ranging from 21 to 27 h were produced. When melatonin was administered in rhythms with periods of 23,24, and 25 h, feeding and locomotion behavior of most birds were rhythmic and synchronized with the exogenous melatonin rhythm. The rest phase coincided approximately with the phase of melatonin availability. Under melatonin cycles < 23 h and > 25 h, fewer birds had synchronized rhythms. Nonsynchronized birds were either arrhythmic or they expressed free-running rhythms. Under melatonin rhythms with periods between 23 and 26 h, the phase-angle difference between defined phases of the behavioral rhythms and the melatonin rhythm became more positive with increasing T. These data are consistent with the hypothesis (a) that periodic exogenous melatonin can substitute, at least to a certain degree, for the endogenous plasma melatonin rhythm normally resulting from the periodic melatonin secretion by the pineal gland, and (b) that this melatonin rhythm acts on another oscillator, possibly the SCN, as part of the overall circadian pacemaking system.
Nonphotic Phase-Shifting and the Motivation to Run: Cold Exposure Reexamined
Authors: Mistlberger Ralph E. , Marchant Elliott G. , Sinclair Sherrill V.
Published: March 2007

Circadian rhythms in rodents can be phase shifted by appropriately timed activity. This may be dependent on motivational context; running induced by a novel wheel is effective, whereas running induced by cold has been inferred to be ineffective. This issue was reexamined using a different cold exposure procedure. On the first day of constant dark, 6 h before usual dark onset, Syrian hamsters were exposed to cold (±4°C) in their home cages, or were confined to novel wheels for 3 h. Activity rhythms were significantly phase advanced by 92 ± 10 min following cold exposure and 86 ± 17 min following novel wheel running, compared to 13 ± 18 min in a control condition. Most hamsters exhibited eating, drinking, and modest levels of wheel running (1367 ± 292 counts/6 h) during and for 3 h after cold exposure. Phase shifts following cold were not affected by food and water deprivation but were significantly attenuated by locking the wheel for 6 h beginning at cold onset (24 ± 12 min). These data indicate that cold-induced running, even at modest levels, is an effective nonphotic Zeitgeber and do not provide support for a hypothesis that motivational contexts determine the phase-shifting value of physical activity.