Melbourne School of Psychological Sciences - Theses
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ItemWellbeing and functioning in emerging adulthood: A longitudinal study of determinants and mechanisms( 2018)During the key periods of adolescence and emerging adulthood, individuals can be particularly vulnerable to experiencing suboptimal wellbeing and functioning. With potential long-term impacts on adult trajectories, early wellbeing promotion is critical. This study aimed to further understand wellbeing development across adolescence and into emerging adulthood, by examining the role of a range of individual and environmental characteristics. The individual characteristics examined included temperament, anxiety symptoms, and depression symptoms. Environmental characteristics included parental responses to emotion expression, parental mental health, stressful life events, and maltreatment. The role of emotion regulation strategies were also explored in relation to the characteristics and wellbeing. The study utilised a longitudinal community cohort from the Adolescent Development Study, recruited from schools across Melbourne, Australia. The sample included 245 families who completed questionnaires across three time points. At time 1 (mean age = 12.45), measures of temperament, depression symptoms, anxiety symptoms, parental depression symptoms, parental anxiety symptoms, and parental responses to offspring emotion expression were completed. At time 2 (mean age = 15.01), adolescents completed measures of stressful life events and maltreatment. They completed emotion regulation and wellbeing measures at the final time point (mean age = 18.83). Predictor variables were factor analysed within each domain in order to provide sufficient representation of the structure of the data. A series of path analyses, controlling for gender and SES revealed that temperament traits, neglect, and abuse predicted wellbeing and functioning outcomes. Bootstrap path analyses (using 95% confidence intervals for the indirect effect) revealed significant associations between the emotion regulation strategies of rumination, distraction, mindfulness, cognitive reappraisal, and expressive suppression with the individual and environmental characteristics, and wellbeing and functioning outcomes. Findings suggest that wellbeing development across adolescence and emerging adulthood is associated with individual characteristics (e.g., temperament), as well as environmental experiences that deviate from adaptive ranges (e.g., neglect). The various patterns found in the study reinforce the salience of examining wellbeing as a multifaceted construct, with aspects of wellbeing potentially having different developmental pathways. Furthermore, emotion regulation strategies may be important for wellbeing pathways, with maladaptive strategies (e.g., rumination) being associated with lower wellbeing and adaptive strategies (e.g. mindfulness) associated with higher wellbeing. Therefore, emotion regulation may be a suitable target for optimising youth wellbeing.
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ItemApplications and extensions of the wisdom of crowds effect( 2018)In traditional studies into the wisdom of the crowd - for example the study by Galton (1907b), which inaugurated this field of research - crowd wisdom tends to be represented as a simple aggregate of individual judgments. This thesis aims to extend research into the wisdom of crowds effect through innovations in methodology, and through applications of the wisdom of crowds approach to non-traditional domains. In Chapter 1 I provide a brief introduction to the concept of the wisdom of the crowd. In Chapters 2 and 3 my focus is on methodological extensions to traditional crowd wisdom research. In Chapter 2 I consider crowd wisdom within the context of binary deterministic forecasting, and argue that a methodological approach common in the field of meteorology should be adopted for use by researchers studying crowd wisdom. To that end, I reanalyze the data from a study by Kurvers et al. (2016) and apply some novel aggregation techniques, which I test using the aforementioned methods from meteorology. I also test Lee and Lee’s (2017) model of binary crowd judgments with new datasets, and conclude that their model is highly robust. In Chapter 3 I incorporate cross-validation methods to conduct a meta-analysis of crowd wisdom studies. In the first part of the chapter I systematically vary trial and test set crowd sizes to draw conclusions about which aggregation methods perform best under which circumstances. In the second part of the chapter I conduct a more complex version of the same analysis, in which the forecasts themselves have costs. In Chapters 4 and 5 my focus shifts to extensions of crowd wisdom research into new domains. In Chapter 4 I consider the domain of sports forecasting, with an emphasis on the forecasting of Australian Rules Football matches. I consider betting market odds as a method of aggregating crowd wisdom about sports matches, and test various methods for cleansing the odds of the bookmaker’s overround so as to obtain a purer measure of crowd wisdom. I conduct a literature review of crowd- and non-crowd-based Australian Rules football forecasting methods, and devise and test a model which aims to be a hybrid of the two approaches. In Chapter 5 I consider the domain of political forecasting. Using a dataset of American polls, I conduct a simulation study of pollster herding. From this study I conclude that even an unsophisticated herding strategy suffices for pollsters to boost their individual performance while undermining the wisdom of the “crowd of polls”. I conduct a literature review of poll aggregation in an Australian context and, within the context of a recent Australian election, compare the forecast accuracy of poll aggregation with a novel model which incorporates crowd wisdom in the form of betting market odds. The election results suggest that betting markets do not provide any additional predictive power beyond that which could be obtained from simple poll aggregation. In Chapter 6 I provide a brief conclusion and outline some promising future directions.
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ItemThe behavioural and neural correlates of learning to sing( 2018)Singing is a ubiquitous and enjoyable human activity in which many individuals participate without any formal training. In recent years, increasing attention has been focused on the possibility that singing training and/or singing-based therapies might induce neuroplastic changes in brain structure and function. Music training has become a significant model for investigating neuroplasticity, yet relatively little is known about singing training-induced neuroplasticity. Case studies and a limited number of group studies in stroke-induced aphasia have suggested a link between singing, particularly in the form of Melodic Intonation Therapy, and neuroplastic changes in brain structure and function. In healthy individuals, cross-sectional studies have shown brain and behavioural differences between trained and untrained singers, but singing-induced neuroplasticity in the healthy brain has not been investigated longitudinally to date. This thesis investigates the impact of singing on the brain and behaviour using a series of longitudinal training studies in both healthy individuals and individuals with stroke-induced aphasia. It also explores a number of methodological issues around singing training and imaging protocols that have repercussions for research in this domain. Standardised electronic singing training protocols were developed for use in these studies, based on Melodic Intonation Therapy principles, and the benefits and drawbacks of these protocols are discussed and recommendations made for future research and development. In the first behavioural experiment, the influence of massed and distributed singing practice on singing abilities, pitch discrimination, and mood was explored in healthy adults. The results suggest that distributed practice had a greater effect on pitch discrimination and mood than massed practice, and thus, distributed practice schedules were used in the remaining training experiments. The second experiment comprised the first longitudinal investigation of the relationship between behavioural improvements in singing and putative singing training-induced functional neuroplasticity in healthy novice singers. Training led to significant improvements in pitch accuracy and vocal quality; however, significant functional neuroplasticity at the group level was not observed. The principal finding of this study was that of substantial individual differences in singing abilities and functional activation for singing, both at baseline and after training. Functional neuroimaging data for overt singing obtained during this study were also used to compare sparse temporal sampling and continuous sampling image acquisition protocols. Sparse temporal sampling has been widely adopted in overt singing and language studies, yet the current findings suggest that sparse sampling might not outperform continuous imaging in this context, while also posing significant analysis challenges. Thus, continuous imaging protocols may be appropriate for some overt response studies. Finally, singing-induced neuroplasticity in the context of language rehabilitation was explored in case studies of individuals with aphasia. A robust ABAB design in one case demonstrated convincingly that singing training (based on Melodic Intonation Therapy) led to functional reorganisation of language that was lateralised toward the right hemisphere. In sum, these studies make a significant contribution to our understanding of singing training outcomes and singing-induced neuroplasticity, and they provide a methodological framework for future basic and clinical research in this field.
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ItemThe neuroprotective effects of music training in epilepsy( 2018)Music is central to modern life and ubiquitous in human culture. A unique functional neurobiological property of music is its greater bilateral representation in the brain, which is hypothesised to account for the proposed relative preservation of music functions in the face of neurological injury, particularly the paroxysmal ictal and inter-ictal network disruption associated with focal epilepsy. Furthermore, specialised training in music may enhance this ‘neuroresilience’ of music functions, in addition to potentially protecting the brain against the effects of future neurological disruption on non-music cognitive abilities. The neurobiological mechanisms underpinning music-related neuroresilience and neuroprotection, however, remain unclear. The current thesis therefore explored these two themes of cognitive resilience and the potential neuroprotective effects of music training, through the critical analysis of extant literature describing music and non-music cognitive abilities in non-musicians (Chapter 2) and musicians (Chapter 4) with neurological disorders, a case-control experimental group study investigating music-related resilience and neuroprotection using the neurological model of focal epilepsy (Chapter 3), and a case study describing the unique preservation of music (but not verbal) memory in a musician with bilateral temporal lobe epilepsy (Chapter 5). Chapter 2 comprehensively reviewed 65 studies examining a range of music functions in pre-surgical or post-surgical non-musicians with focal epilepsy. Overall, the findings of this review provided evidence that music cognitive deficits are relatively common in non-musicians with epilepsy, with many domains affected in at least half of the patient cohorts. Considerable variability in impairment was evident, however, with post-surgical epilepsy cohorts tending to exhibit more frequent deficits than pre-surgical patients. This was especially evident for music functions associated with broader, multi-domain networks (e.g., melodic and musical emotion processing) compared to lower-level musical processing (e.g., pitch discrimination). A rightward asymmetry was observed for many music deficits, particularly for the domains of melodic processing and singing. Although these results contradicted the idea of music’s resistance to disease and the benefits of bilateral functional organisation, a number of limitations were identified within this literature, which made the interpretation of the findings challenging. Critically, examination of music cognitive abilities in isolation from non-music functions such as language and verbal memory does not allow for the comparison of the relative neuroresilience of music versus non-music skills. Consequently, the case-control group study presented in Chapter 3 assessed music and non-music cognition in focal epilepsy patients with and without music training, and healthy control participants with and without music training. The results indicated a pervasive pattern of verbal cognitive impairments (e.g., verbal fluency, abstract reasoning, and memory) and select music cognitive difficulties (melodic discrimination and metre identification) in epilepsy non-musicians compared to controls (musicians and non-musicians combined). In contrast, epilepsy musicians displayed preserved verbal cognition on all measures except verbal fluency, and no significant deficits in music cognition. The results were interpreted as a neuroprotective effect of music training in the epilepsy musician group, which benefited cognitive abilities that likely share processing components and neural substrates with the skills required to learn to play an instrument. This includes training-related enhancement of brain regions in fronto-temporo-parietal networks and their underlying structural connections (e.g., superior longitudinal and arcuate fasciculi), which support core cognitive processes such as working memory and executive control. This interpretation was strengthened by the finding that musicians who began training earlier in life (<=7 years old) tended to display greater benefits for verbal cognitive abilities. Furthermore, the overall more pervasive pattern of non-music cognitive deficits in patient non-musicians supported the notion of music’s greater relative resilience to the cognitive consequences of epilepsy. The critical literature review in Chapter 4 extended the findings of Chapter 3, by synthesising the evidence from 87 studies (comprising 99 unique cases) of musicians with either epilepsy, stroke, dementia, herpes simplex virus encephalitis, and patients undergoing surgical resection of brain tumours. The collated findings across populations indicated that impairment was generally more commonly reported for non-music compared to music cognitive functions, and that the frequency of music and non-music impairments varied as a function of disease aetiology. A comparison between epilepsy, stroke, and dementia cases revealed the greatest levels of music and non-music functional preservation in epilepsy musicians. Moreover, epilepsy musicians demonstrated fewer overall deficits in music versus non-music domains, with only select impairments in language, verbal/visual memory, attention, and music reading. These findings reinforced the results from Chapter 3, highlighting the relative neuroresilience of music functions, and the protective effects of music training in epilepsy. Given the more widespread patterns of impairment observed in stroke and dementia cases, however, music training does not appear to provide neuroprotection for untrained abilities (i.e., ‘far’ transfer) in patients with sudden acute neurological insult (stroke) or diffuse and progressive cerebral atrophy (dementia). Finally, Chapter 5 described the case of a particularly interesting musician with bilateral temporal lobe epilepsy and hippocampal sclerosis, who had taken part in the group study from Chapter 3. This musician (BK) exhibited a profound discrepancy between his intact melodic learning and memory skills and severely impaired verbal and visual memory, illustrating the possible upper limits to the potential for music training to compensate for bilateral temporal lobe disruption. BK’s preserved music memory was intriguing, and it was hypothsised that he was engaging the dorsal fronto-temporal circuit implicated in working memory and articulatory rehearsal, to facilitate the encoding, storage, and retrieval of musical information. To investigate this further, BK was assessed on a task of melodic learning with articulatory suppression, involving trials of digit span forward serial recall after the presentation of each of eight short, novel melodic sequences that he was to remember. Comparison with his performance on the same task without phonological interference revealed a disruptive effect of the extraneous auditory information for remembering atonal melodic sequences. This suggested that articulatory rehearsal was an effective encoding strategy for processing and remembering these stimuli, implicating at least partial mediation of BK’s music memory via training-enhanced working memory circuits. These intriguing findings provided further evidence for the beneficial effects of music training-related neuroplasticity for multiple music and non-music cognitive systems, in addition to emphasising the relative resilience of music functions, against the effects of even severe bilateral network disruption. As suggested by Chapter 4, these benefits appear to be unique and specific to epilepsy, and do not provide the same level of cognitive sparing in musicians with non-epileptic bilateral neurological damage. This thesis discusses the above findings in the context of methodological limitations in the music neuroscience literature, including a dearth of group studies comparing musicians and non-musicians with neurological disorders. These findings have critical implications for music education, emphasising the importance of access to music within schools, in light of the evidence that engaging in music learning early in life may be associated with neuroplastic changes that benefit the brain and cognition later in life. In addition, examination of the possible therapeutic effects of music training in individuals with epilepsy may shed further light on the neurobiological mechanisms underpinning music-related neuroplasticity, and how time-sensitive these processes are in relation to the development of seizures.
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ItemExpression of the broader autism phenotype in epilepsy( 2018)Converging evidence from epidemiological, family, and genetic studies supports that epilepsy and autism spectrum disorder (ASD) share underlying mechanisms. However, uncovering these mechanisms has been challenging because of the confounding influence of intellectual disability (ID) in studies of people with co-occurring epilepsy and ASD. To overcome this, this thesis explores whether studying the broader autism phenotype (BAP) in people with epilepsy (PWE) offers an alternative approach to uncovering shared mechanisms of epilepsy and ASD. This was achieved through four studies that examine the profile of the BAP in PWE relative to community members and relatives of individuals with ASD (ASD-relatives). Study 1 consists of a systematic review and meta-analysis of the literature examining facial emotion recognition (FER) and theory of mind (ToM) difficulties—two BAP traits—in PWE and ASD-relatives compared to controls. Results support poorer FER and ToM in PWE and ASD-relatives than controls, with greater difficulties in PWE than ASD-relatives, and limited contribution from secondary effects of seizures (e.g., neural network disruption secondary to repeated seizures, effects of anti-epileptic drugs). These results suggest that reduced FER and ToM in PWE are underpinned by shared mechanisms of epilepsy and ASD interacting with epilepsy-specific mechanisms to cause more severe difficulties. For Studies 2–4, 103 adults with epilepsy without ID (51 temporal lobe epilepsy; 40 genetic generalised epilepsy; 12 unclassified; Mage = 37.4 years, SD = 12.5; MIQ = 104.0, SD = 12.4; 55 females) were prospectively recruited from epilepsy clinics in Melbourne, Australia from 2013 to 2015, as well as 58 local community members (Mage = 39.6 years, SD = 14.6; MIQ = 113.0, SD = 11.6; 38 females). Participants were classified with and without the BAP as a categorical construct by combining data from an interview and validated questionnaire, and individual BAP traits were assessed using targeted measures. Study 2 suggests that compared to published estimates from large population-based samples, the BAP as a categorical construct—a more specific marker of ASD susceptibility mechanisms than individual BAP traits—is more prevalent in PWE (21%) than the general population (6%), commensurate with ASD-relatives (15%). This and evidence that PWE with the BAP have a similar BAP trait profile to community members with the BAP supports that the BAP reflects ASD features in PWE that may be underpinned by shared causal mechanisms of epilepsy and ASD. Studies 3 and 4 assess the extent to which shared mechanisms of epilepsy and ASD or epilepsy-specific mechanisms likely underpin pragmatic language, ToM, and empathy difficulties in PWE. Results suggest that pragmatic language and ToM difficulties are more pervasive in PWE, presenting similarly in PWE with and without the BAP and in community members with the BAP, whereas empathy difficulties are unique to PWE and community members with the BAP. Interpreted using the multiple deficit model (Pennington, 2006), these findings suggest that pragmatic language, ToM, and empathy difficulties reflect ASD susceptibility mechanisms in PWE and that the former two are sensitive to ASD risk factors of lesser effect. Combined, these studies offer initial support for the proposal that studying the causes of BAP traits in PWE can inform on shared mechanisms of epilepsy and ASD independent of ID. Thus studying the BAP offers a new avenue to uncovering shared mechanisms of epilepsy and ASD, which may ultimately have positive therapeutic implications for PWE and individuals with ASD.
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ItemMapping common ground: relationships between sensory-processing sensitivity, introversion-extraversion, openness to experience and intelligence( 2018)Sensory-processing sensitivity encompasses the overlapping characteristics of low sensory threshold, heightened awareness of and reactivity to sensory stimuli, heightened top-down inhibitory processes, and deep processing of sensory information. Both introversion and openness to experience (also encompassing the narrower facet of intellect) have been separately linked to markers of sensory-processing sensitivity, even though introversion and openness/intellect are usually negatively correlated with each other. Introversion and openness/intellect have rarely been included simultaneously in analyses of relationships with sensory-processing sensitivity. Including these two personality factors simultaneously in analyses is important, given the negative bivariate relationship between introversion and openness/intellect can obscure positive relationships with other variables, through statistical suppression effects. The Highly Sensitive Person Scale is a self-report measure of sensory-processing sensitivity of potential utility for further researching relationships between sensory-processing sensitivity, introversion and openness/intellect. However, there is lack of clarity regarding the factor structure of the Highly Sensitive Person Scale, with different studies reporting different factor solutions. There are several methodological issues that may have contributed to these discrepancies, and concerns that neuroticism or negative affect could contribute to spurious factors emerging for this scale. However, no known prior studies have addressed these potential issues. A series of studies were undertaken as part of this thesis, investigating the factor structure of the Highly Sensitive Person Scale, and relationships between these factors and introversion, openness/intellect, and intellectual giftedness. The final study in this thesis then sought to test whether introversion, openness/intellect or cognitive reasoning ability were related to non-invasive, physiological markers of sympathetic and parasympathetic responsivity: low frequency and high frequency heart rate variability. Studies undertaken for this thesis employed robust structural equation modelling techniques with data from a range of new or existing adult samples recruited through the community and online. All analyses controlled for neuroticism or subjective wellbeing, and for other variables where relevant, and included introversion and openness/intellect simultaneously in analyses. Results of these analyses showed that the Highly Sensitive Person Scale is best represented by three factors, Low Sensory Threshold, Situational Sensitivity and Aesthetic Sensitivity. This factor structure was unaffected by neuroticism or emotional wellbeing, and was replicated across three samples. Low Sensory Threshold was consistently, positively related to both introversion and openness/intellect. This relationship was mediated by Situational Sensitivity for introversion and by Aesthetic Sensitivity for openness/intellect. Both introversion and openness/intellect were also positively related to intellectual giftedness, when including both of these personality variables simultaneously in the model. However, contrary to expectations, there were no significant relationships between Highly Sensitive Person Scale factors and intellectual giftedness. Both introversion and openness/intellect were positively related to low frequency heart rate variability during some conditions, and openness/intellect was positively related to high frequency heart rate variability under most conditions. Cognitive reasoning had a positive relationship with low frequency heart rate variability for males, and a negative relationship with high frequency heart rate variability for females. The above findings suggest that heightened sensory-processing sensitivity may be accompanied by feeling potentially overactivated by external stimuli or by a desire to engage with aesthetic or cognitively interesting stimuli. The former is associated with introversion and the latter with openness/intellect. Some highly sensitive individuals may experience both Situational Sensitivity and Aesthetic Sensitivity aspects of sensory-processing sensitivity, given the pattern of relationships found. Common ground shared between introversion, openness/intellect and correlates such as intelligence may have important implications for further understanding these personality variables, especially given the current interest by personality theorists in mechanisms shared by extraversion and openness/intellect. The model of relationships found in this thesis could provide a useful framework for future research, and for practitioners who work in areas relevant to sensory-processing sensitivity.
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ItemAffective functional brain development from late childhood to early adolescence: interactive effects of adrenarcheal timing and parenting, and associations with internalising and externalising symptoms( 2018)Background: The childhood to adolescent transition is a period of marked brain development and increases in mental health difficulties. Both early pubertal timing and adverse parenting styles have been consistently associated with internalising and externalising problems in childhood and adolescence. Moreover, there is some emerging evidence that that the interplay between these factors may be important in predicting risk for such difficulties. However, most of this research has focused solely on the timing of gonadarche (a later stage of puberty), thereby neglecting the potential role of adrenarcheal timing (an earlier pubertal stage) in relation to mental health. Further, little is known regarding potential neurodevelopmental mechanisms underlying these complex associations. Parenting styles and pubertal development have separately been associated with affective neural function, particularly in brain regions important for emotion processing and regulation. Similar aspects of affective neural function have been suggested as important in predicting internalising and externalising difficulties. Thus, investigating interactive effects of parenting and adrenarcheal timing in relation to affective brain function and its development may be a promising way forward in understanding the complex associations between these factors and adolescent mental health. Aims: Broadly, this thesis aimed to examine interactive effects of adrenarcheal timing and parenting styles on internalising and externalising symptoms, as well as affective function and its development over the transition from childhood to adolescence. It further explored the mediating role of affective brain function and its development in linking parenting and adrenarcheal timing to symptom levels during this period. Method: Participants were drawn from a sample of 128 children selected from a larger longitudinal cohort study, and classified as relatively early or late in adrenarcheal timing based upon levels of adrenal hormones in late childhood compared to same-age peers. At two time points (ages 9 and 12), participants completed an affective face fMRI task involving passive viewing of happy, angry, fearful and calm faces. Their parents completed the Alabama Parenting Questionnaire, reporting on five dimensions of parenting (positive and negative), and the Child Behaviour Check-List measuring child internalising and externalising symptoms. Data were subjected to cross-sectional and longitudinal analyses using factorial models. Data analyses were conducted over three stages: first, the interactive effects of parenting and adrenarcheal timing in childhood were examined in relation to concurrent levels of internalising and externalising symptoms, as well as to prospective symptom levels into early adolescence; second, the interactive effects of parenting and adrenarcheal timing in relation to affective brain function, and in turn symptom levels in childhood, were examined; and third, the interactive effects of parenting and adrenarcheal timing in relation to development in affective brain function from childhood to early adolescence, and in turn symptoms in early adolescence, were examined. Results: Findings revealed a number of interactive effects of parenting styles (particularly corporal punishment) and adrenarcheal timing in relation to concurrent internalising and externalising symptoms in childhood, as well as to affective brain function and its development into early adolescence. Notably, in the context of higher exposure to corporal punishment, children with late adrenarcheal timing showed patterns of neural activation in response to affective stimuli that were suggested to be less adaptive. Specifically, in childhood, late developing females whose parents reported higher levels of corporal punishment showed dampened neural activation to positive stimuli in reward circuitry (e.g. insula), and to negative stimuli in regulatory circuitry (e.g. VLPFC, DLPFC, and frontal pole). Further, irrespective of sex, late developing children showed increased superior frontal gyrus activation over the transition from childhood to early adolescence. Moderated mediation models indicated that increased superior frontal gyrus activation over time in late children mediated the relationship between corporal punishment in childhood and later internalising symptoms. Significance: The research conducted in this thesis represents the first investigation of interactive effects of adrenarcheal timing and parenting styles in relation to affective brain function and its development from childhood to early adolescence, and in turn internalising and externalising symptoms during this period. The development of mental health difficulties is thought to result from multiple complex pathways, which may differ across individuals. In line with this notion, the findings of this PhD research illustrate the importance of examining the interplay between environmental and biological factors in order to understand patterns of brain development and mental health during the transition from childhood to adolescence. They also demonstrate the importance of investigating longitudinal patterns of neural and psychological development in order to increase understanding of how individual trajectories may relate to risk of resilience.
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ItemCerebral arterial asymmetries in the neonate( 2018)In spite of the symmetric embryological origins of many paired anatomical structures, the human body is inherently asymmetric. Adult studies reveal leftward asymmetries in the structure and haemodynamics of supra-aortic extracranial and intracranial vessels. At the level of the carotid arteries, these asymmetries are meaningfully related to hand preference. The existence of an arterial correlate of handedness in adults poses a key question. Do lateral biases in blood supply to the brain arise as a consequence of language acquisition and the emergence of manual dexterity, or do they predate these lateralised functions? In essence, is the ground plan of adult arterial asymmetries discernible in neonates? To our knowledge, this is the first time that neonatal cerebrovasculature has been imaged non-invasively at a sufficient level of resolution to accurately measure vessel diameter and corresponding blood flow. A new transcranial Doppler ultrasonography dual-view scanning protocol, with concurrent B-flow and Pulsed-wave imaging, was used to acquire multivariate data on neonatal middle cerebral arterial structure and function. Detailed diametric measurements were taken of the trunk origin and terminus using RadiAnt DICOM Viewer (64-bit) imaging software. Haemodynamic parameters of the Doppler waveform were recorded, including peak systolic and end-diastolic velocity, resistive index, pulsatility index, and blood flow volume. This dissertation documents significant asymmetries in the middle cerebral artery origin and distal trunk of healthy term neonates (n = 97). A systematic leftward arterial dominance was found in vessel calibre and cortically directed blood flow. The arterial asymmetry was also meaningfully related to the supine head orientation bias, an endogenously driven behaviour that reliably predicts future hand preference. By and large the arterio-postural relationship is characterised by larger arterial diameters and higher blood flow volumes in the left hemisphere of right-postured neonates. Deviations from this typical arterio-postural association begin to unfold increasing lateral heterogeneity in head turning behaviour. In left turning newborns, the coherence of the arterio-postural relationship is dependent on the magnitude of arterial asymmetry across the midline of the brain, and maintenance of these larger arterial diameters from the proximal to distal regions of the right trunk. Commensurately asymmetric haemodynamic vulnerabilities were identified. Endothelial wall shear stress was asymmetric across the midline and varied according to geometric and behavioural lateralisation. Shearing asymmetries systematically disadvantaged left hemispheric endothelium with lower left-than-right peak systolic and end-diastolic endothelial shearing forces in neonates with larger left-sided arteries and with right-sided head postures. Unfavourable shearing forces, which are a by-product of the arterial asymmetries described here, might contribute to a greater risk of cerebrovascular pathology in the left hemisphere in neonates and adults. We conclude that arterial structure and blood supply in the brain are laterally asymmetric in newborns, predating the advent of neurobehavioral expressions of cerebral lateralisation, such as language and manual dexterity. The empirical support for an arterial correlate for lateralised cerebral function has key implications for the understanding of the origins of human cerebral organisation from evolutionary and ontogenetic perspectives.
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ItemThe role of biological stress and inflammation in sleep and mental health: a longitudinal perspective among at-risk adolescents( 2018)Objective: A healthy functioning body relies in part on a delicate balance between the immune and neuroendocrine (or immuno-endocrine) systems. Sleep disturbance, anxiety, and depression have each been associated with disruptions to the immuno-endocrine system. Recent literature also suggests that dysregulations of the immuno-endocrine system may precipitate sleep disturbance and mental health issues, suggesting a bi-directional role for immuno-endocrine functioning in sleep and mental health. Poor sleep, mental ill-health, and disturbed immuno-endocrine functioning have each been linked to a range of psychosocial, psychiatric, and medical comorbidities including risk for stroke, diabetes, and cardiovascular disease, greater medical expenses, increased substance use, disruptions to interpersonal relationships, poorer vocational outcomes, increased family violence, and more chronic mental and physical health conditions throughout the lifespan. While associations between sleep, mental health, and immuno-endocrine functioning are well- established in adults, less is known about immuno-endocrine functioning in the context of adolescent sleep and mental health, despite high prevalence rates of poor sleep, anxiety, and depression among youth. Further, targeted, preventative treatment interventions for adolescents at-risk of poor sleep, anxiety, and depression may buffer against the progression of mental health issues, as well as immuno-endocrine system dysregulation. However, no study to date has investigated the longitudinal impact of an early-intervention, psychological treatment intervention on biomarkers of immuno-endocrine health in a sample of at-risk-for- depression adolescents. Further, no study with youth has investigated the potential mechanistic role of immuno-endocrine dysregulation in common disease progressions from anxiety issues to depression onset, poor sleep issues to anxiety onset, or poor sleep issues to depression onset. Therefore, the aims of the current thesis were to investigate these gaps in the literature. Method: As part of a larger, multi-center and comprehensive ‘Sleep and Education: learning New Skills Early’ (SENSE) Study, the current thesis investigated the immuno-endocrine functioning of at-risk adolescent participants (n=122, 73 female) in the SENSE Study. The SENSE Study was a two-year, early intervention, randomized-control trial (RCT) researching the impact of a seven-week cognitive-behavioral and mindfulness-based intervention for adolescents who endorsed sleep disturbances and/or anxiety symptoms, known risk factors for the development of depression. The overarching aim of the SENSE Study was to investigate whether a multicomponent sleep intervention, which combined operant conditioning, stimulus control, sleep hygiene psychoeducation, cognitive therapy, and mindfulness-based techniques, would serve as a preventative measure for at-risk adolescents against the development of depression two years post-intervention. Participants were recruited from schools within the Melbourne metropolitan area and invited to participate if they endorsed elevated anxiety and/or poor sleep symptoms, and had no prior history of major depression. At baseline (Time 1; T1) participants (aged 12 to 16 years, mean aged 12.71 years) provided saliva samples across two consecutive days and completed a range of sleep and mood assessments including semi- structured mental health clinical diagnostic interviews, self-report questionnaires, and wrist- actigraphy (an objective measurement of sleep). Participants were randomized into either a seven-week sleep treatment intervention (n=63) or an active study skills control intervention (n=59). Participants completed the same assessments (excepting saliva sample collection) at post-intervention (Time 2; T2), and were assessed again (including saliva sample collection) at two-years post-intervention (Time 3; T3) when participants were aged between 14 and 18 years (mean aged 16.82 years). Thus, immuno-endocrine data was collected at T1 and T3. The current thesis investigated several cross-sectional and longitudinal associations among measures of sleep and mental health with diurnal levels of salivary C-reactive protein (CRP) and cortisol, biomarkers representative of overall systemic functioning of the immune system (CRP) and the neuroendocrine system (cortisol). This project was also the first to use the cortisol to CRP ratio as a measure of inter-system immuno-endocrine organization in the context of sleep and mental health among a sample of youth and in a longitudinal setting. First, for cross-sectional analyses, it was predicted that greater sleep disturbance and mental health issues would be associated with greater disruptions to the immuno-endocrine system (as indexed by higher morning and evening levels of CRP, lower morning and higher evening levels of cortisol, and less homeostatic cortisol to CRP ratio levels). Second, it was predicted that compared to participants in the control intervention, participants in the treatment intervention would display healthier immuno-endocrine functioning at two-year follow-up. Third, it was predicted that dysregulated immuno-endocrine functioning would aid in the progression of 1) anxiety issues to depression onset, 2) poor sleep issues to anxiety onset, and 3) poor sleep issues to depression onset. Finally, it was predicted that sex would be a moderator in all analyses. Results: First, cross-sectional multivariate regression analyses indicated that participants who self-reported longer sleep onset latency (the period of time attempting to fall asleep) at T1 had more blunted morning cortisol levels at T1, even when controlling for common covariates used in the literature. Sex did not moderate this relationship. Second, one-way analyses of covariance (ANCOVA) were conducted to investigate treatment effects on salivary levels of CRP and cortisol, which revealed no statistically significant effects of treatment conditions on biomarkers measured at T3. Two-way ANCOVAs investigating the effect of treatment and sex were also not significant. Third, longitudinal analyses revealed that participants with greater bedtime variability at T1 were less likely to experience depressive symptoms at T2, and more likely to experience a clinical anxiety episode by T3, although levels of CRP and cortisol did not mediate these paths. Finally, participants with an anxiety disorder at T1 were 4.58 times at risk of developing a depressive disorder by T3, although levels of CRP and cortisol did not mediate this path. Sex did not moderate any longitudinal analysis. However, a higher T1 cortisol to CRP ratio (indicative of elevated levels of cortisol relative to attenuated levels of CRP) significantly predicted the onset of a first-ever depressive disorder by T3, even when controlling for T1 depressive symptoms. Conclusion: The current study adds to the literature on links between sleep, mental health, and immuno-endocrine functioning in youth, a relatively new area of research. Results highlight important methodological considerations that future treatment studies should incorporate, considerations which may encourage benefits to the adolescent immuno-endocrine system. The continuation of immuno-endocrine biomarker assessment among youth populations will advance the knowledge of the potential biological underpinnings of sleep disturbance and poor mental health. Refinement of treatment interventions may pave the way for such underlying mechanisms to be harnessed and recruited along the path to treatment outcome goals. Moreover, that perceived sleep onset latency but not objective sleep onset latency was associated with more blunted cortisol levels suggests that interventions designed to target negative or inaccurate assessments of sleep may buffer against neuroendocrine health consequences. Lastly, the finding that adolescents with a more disorganized immuno- endocrine system (i.e., a higher cortisol to CRP ratio) were more at risk of developing depression is novel, and suggests that the cortisol to CRP ratio could serve as a disease risk biomarker for first-onset depression. Early identification of individuals at high risk of depression may prevent medical and psychiatric comorbidities throughout the lifespan.
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ItemThe role of presentation media in the moral domain( 2018)As the prevalence of text-based and computer-mediated communication has increased, a number of researchers in psychology have identified ways in which medium affects perception and behaviour. Yet, there is very limited research attention by moral psychology researchers on the topic of medium effects. This thesis presents a systematic exploration of the ways in which medium might impact moral outcomes. The first stream of this thesis examined the role of medium in moral outcomes in a specific example of text-based communication, computer-mediated-communication (CMC). I utilised a theoretical framework from the CMC literature, the cues-filtered-out approach, as a means of understanding moral behaviour in the context of CMC. Overall, there was limited support for this theoretical approach; however, both studies in this stream identify ways in which medium affects positive and negative moral behaviours and moral perception. Study 1 demonstrated that listening to the voice of someone who disagrees with your political opinion can lead to more aggression and paradoxically, humanisation, compared to reading an equivalent text passage. Study 2 shows that, under certain circumstances, reading a dating profile can lead to more self-disclosure compared to watching an equivalent video. Study 2 also found that in the text condition some aspect of person perception was exaggerated. In the second stream of this thesis, I took a more basic approach to exploring the effect of presentation medium on moral outcomes. First, in Study 3, I conducted a systematic review of the moral psychology literature that revealed that more than 92% of research on moral judgements relied only on text stimuli. Given that text stimuli lack the rich variety of morally-relevant social and contextual cues available in everyday interactions, I argue that a consequence of this pervasive ecological invalidity may be that moral psychological theories are mischaracterized by an overreliance on cue-impoverished moral stimuli. I address this limitation by developing an ecologically valid and cue-rich, moral video stimulus set with matching text (Study 4). Next, I use this stimulus set to explore the role of medium on moral judgment, perception, and affect (Study 5). I found that judging moral transgressions in a cue-poor medium (i.e., text) results in a pattern of moral judgement and affective responses (i.e., wrongness, moral foundation categorisations, arousal, and humanness) that did not generalise to a more ecologically valid medium (i.e., video). Overall, there is evidence that presentation medium affects a number of morally relevant outcomes (i.e., wrongness, arousal, moral foundation categorisation and humanness), although the size of these effects was smaller than expected (in most cases) and the directionality of some effects was contrary to expectations. Specifically, when content was presented via text (compared to video) judgements were harsher, but (contrary to expectations) the content was less arousing, and there was greater consensus on why a moral transgression was wrong (i.e., moral foundation categorisation). Contrary to expectations, when content was presented via text (compared to video) both perpetrators and victims were also judged as more human. There was no evidence to suggest that the presentation medium of the moral content affected perceptions of causality, blame, nor evoked empathy (cognitive or emotional). Across five studies, I find evidence that the medium by which we communicate or present a stimulus shapes morally relevant outcomes. However, the exact mechanism by which medium affects moral outcomes remains unclear, that is, there was limited support for CMC theories in accounting for medium effects of a positive or negative moral behaviour. Importantly, contrary to dominant rhetoric in the CMC literature and general population, text as a presentation or communication medium does not necessarily lead to more negative outcomes. Instead, I find evidence that text can have positive implications for moral behaviour: facilitating more moral judgment, less antisocial behaviour (e.g., aggression), and more positive moral behaviours (e.g., self-disclosure). Overall, this thesis has identified the importance of presentation medium in moral psychology and identified a fertile ground for future research.