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Precision Examination of Real-World Stress and Behavior Using Deep Digital Phenotyping
No full textLife stress has been consistently linked to poor mental health outcomes, but we know comparatively less about the more proximate impacts of life stress on daily affect and behavior. The current dissertation leverages recent advances in digital technology and analytical approaches to examine real-world life stress and its affective and behavioral correlates in a cohort of first-year college students naturally exposed to multifaceted stressors as they transitioned to college life. For a full academic year, participants provided continuous accelerometer data from an actigraphy wristband for the objective estimation of sleep duration and waketime activity. Additionally, participants used their phones to complete daily self-reports of perceived stress sources, affect, behavior, as well as the main events of their day, and completed periodic web-based assessments of global psychopathology symptoms. Similar data was collected in a timely 3-month follow-up study as the same participants underwent a new, unprecedented life transition: the beginning of the COVID-19 pandemic. Following a general review of relevant background literature in Chapter 1, novel insights into real-world life stress drawn from these datasets are offered across three papers presented in Chapters 2 through 4.
Chapter 2 (Paper 1) examines fluctuations in stress, affect, and behavior over the course of the first year of college. Negative emotions, sleep patterns, and academic and social activity varied substantially over the course of the year as well as between individuals. Critically, while academics were a common source of stress for all students, a vulnerable subgroup reporting greater frequency of perceived social stress went on to report the highest global clinical symptoms at the end of the year, suggesting dissociable effects of different stress sources on mental health. Two years later, during the COVID-19 pandemic, the first-year subgroup with highest distress again stood out by frequent social stress and elevated clinical symptoms, suggesting that focus on sustained interpersonal stress, relative to academic stress, may be especially helpful to identify students at heightened risk for psychopathology.
Chapter 3 (Paper 2) introduces a novel individual-level linear model (iLM) to estimate day-to-day associations between perceived stress levels and actigraphy-derived sleep duration within individuals and unbiased by the group. While stress and sleep duration were inversely related in most participants, the iLM revealed that the temporal direction of these associations is person-specific, identifying a variety of individual phenotypes that may account for the diverse group-level findings reported in prior literature: for some, elevated stress in the day was associated with shorter sleep later that night; for others, shorter sleep was associated with elevated stress the next day; others showed both directions of associations, and some showed no association. Paired with intensive longitudinal data, our individual-level model provides a precision framework for the estimation of stable real-world behavioral and psychological dynamics, and may support the personalized prioritization of intervention targets for health and wellbeing.
Chapter 4 (Paper 3) investigates the proximate correlates of academic and social stressful events on daily affect and behavior within individuals. Experiences of stress were characterized from participants’ daily voice diaries narrating the main events of the day, using a combination of human labeling and large language models fine-tuned for sentiment analysis and topic modeling. Multilevel models assessing within-person associations found that days with academic stressful events were characterized by shorter sleep duration and decreased physical activity, as well as by reduced social interaction and increased time spent on schoolwork. Meanwhile, days with social stressful events were not systematically associated to changes in behavior, but they stood out by heightened negative affect, above and beyond the effect of academic events. Our results suggest that academic and social dimensions of life stress may have distinct signatures on daily affect and behavior, which in turn may go on to shape individuals’ long-term wellbeing.
Chapter 5 discusses the main contributions and limitations of this body of work. In all, the current dissertation provides valuable insights into the effects of life stress on real-world emotions, behavior, and overall wellbeing at multiple timescales. Our approach offers a foundation for the characterization of life dynamics at both the individual and the group levels, with potential implications for the development of precision health and wellbeing interventions
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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Examining the Organization and Functions of Parallel Association Networks within Individuals
No full textIn our daily lives, we often recall details of our past experiences, consider friends’ feelings, imagine novel scenarios, and flexibly communicate with others. These impressive cognitive abilities – for memory, social reasoning, prospection and language – are hallmarks of our species. And all have been linked to regions of association cortex in the human brain. Association regions also show disproportionate evolutionary expansion and prolonged postnatal development, making them particularly intriguing targets for understanding how human brains support our advanced cognitive abilities.
Prior work commonly attributed broad swaths of association cortex to large, multi-functional networks. More recently, pairing advances in neuroimaging resolution with precise within-individual techniques has revealed multiple interwoven networks distributed across association zones. This raises the question: could dissociable networks support distinct higher-order functions?
In this dissertation, I explore this question by examining the organization and functions of individually-defined association networks, with particular focus on three distinct networks that differentially support higher-order functional domains. In three central chapters, I describe growing evidence that distributed, parallel networks occupy association zones within individuals and that three of these networks (termed DN-A, DN-B and LANG) differentially support scene construction, social and language comprehension tasks.
Chapter 1 examines how parallel, interwoven networks DN-A and DN-B are differentially recruited by episodic projection and theory of mind task contrasts. Chapter 2 explores the functional properties of the LANG network in relation to DN-A, DN-B and other juxtaposed association networks, including selective response to a language comprehension task. Chapter 3 explores network functions by building on existing neuroimaging data with novel measures of trial-level variation, providing evidence of DN-A’s differentiation from nearby networks and role in scene construction processes.
Collectively, these chapters illustrate functional heterogeneity between parallel, distributed networks. These findings, paired with the networks’ similar spatial motif, also raise the possibility that the multiple networks originated from a singular archetype. The final Discussion presents the Expansion-Fractionation-Specialization hypothesis to account for these observations: evolutionary expansion of human association cortex may have allowed for a prototype distributed network to fractionate into multiple specialized networks. Human development may recapitulate fractionation and specialization when these abilities emerge
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Memory and Executive Function in Aging and AD Multiple Factors that Cause Decline and Reserve Factors that Compensate
No full textAbstractMemory decline in aging results from multiple factors that influence both executive function and the medial temporal lobe memory system. In advanced aging, frontal-striatal systems are preferentially vulnerable to white matter change, atrophy, and certain forms of neurotransmitter depletion. Frontal-striatal change may underlie mild memory difficulties in aging that are most apparent on tasks demanding high levels of attention and controlled processing. Through separate mechanisms, Alzheimer's disease preferentially affects the medial temporal lobe and cortical networks, including posterior cingulate and retrosplenial cortex early in its progression, often before clinical symptoms are recognized. Disruption of the medial temporal lobe memory system leads directly to memory impairment. Recent findings further suggest that age-associated change is not received passively. Reliance on reserve is emerging as an important factor that determines who ages gracefully and who declines rapidly. Functional imaging studies, in particular, suggest increased recruitment of brain areas in older adults that may reflect a form of compensation
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