Graduate Theses & Dissertations


Comparison of Dehydration Techniques for Acute Weight Management in Rowing
Mild sauna dehydration and fluid abstinence were investigated as weight loss strategies for lightweight rowers. Rowers (N=12) performed a power test, an incremental VO2max test, and a visuomotor battery: once euhydrated, once following sauna dehydration (SAU), and once following fluid abstinence and then sauna dehydration (FA). The percent body mass change (%BMC) achieved, %BMC attributable to sauna dehydration, and %BMC attributable to fluid abstinence were used within linear mixed effects models to predict hydration and performance variables. Sauna and overnight dehydration exerted indistinguishable effects on plasma osmolality, urine osmolality and thirst (p > .05). Fluid abstinence but not sauna dehydration was related to lower power production on the power test (b = 12.14W / 1%BMC, FA = 673.46 ± 79.50, SAU = 683.33 ± 72.08, p = .029), a lower total wattage produced on the incremental VO2max test (b = 4261.51W / 1%BMC, FA = 71029.58 ± 16256.56, SAU = 74001.50 ± 14936.56, p = .006), lower wattages at 2 mmol/L (b = 27.84W / 1%BMC, FA = 180.74 ± 40.27, SAU = 190.82 ± 50.79, p < .001) and 4 mmol/L (b = 20.45W / 1%BMC, FA = 221.90 ± 52.62, SAU = 238.89 ± 40.78, p = .002) blood lactate, and slower movement time on a visuomotor task (b = -38.06ms / 1%BMC, p = .004). Mild fluid abstinence but not sauna dehydration reduces rowing performance when two-hour rehydration is allowed. Author Keywords: crew, fluid, hydration, lightweight, sauna, weight
Impaired contextual fear discrimination learning after long-term amygdala kindling
Cognitive impairments, such as memory loss, are a frequent and devastating co-morbidity associated with epilepsy. The neurobiological mechanisms through which recurrent seizures induce cognitive impairments are not well understood. New neurons born after seizures develop abnormal morphological and functional characteristics that promote network hyperexcitability and hippocampal dysfunction. Previously, we found that kindling dramatically increases the rate of neurogenesis at early stages of seizure development, followed by a long-term suppression at later stages. These changes in the rate of cell proliferation coincides with aberrant modifications in the migration, excitability, and functional integration of these new neurons. It has been suggested that the long-term consequences of seizure-induced neurogenesis contributes to the development of cognitive impairment seen in chronic epilepsy. However, direct experimental evidence has been limited. The present series of experiments sough to determine if blocking aberrant seizure-induced neurogenesis can reduce cognitive deficits associated with chronic epilepsy. Our findings suggest that chronic seizures impair the ability of rats to differentiate between similar contexts. In addition, blocking aberrant seizure-induced neurogenesis through treatment with the cytotoxic agent temozolomide was capable of preventing some of the deficits in context discrimination learning when neurogenesis levels were reduced to non-epileptic control levels. This research provides further support of targeting aberrant neurogenesis as a novel treatment to restore cognitive functioning in individuals living with epilepsy. Author Keywords: Amygdala kindling, Dentate gyrus, Hippocampus, Neurogenesis, Pattern separation, Seizures
Is semantics activated automatically? Evidence from the PRP paradigm
Three experiments examined whether semantics is activated automatically by testing whether Arabic digits (e.g., 4), number words (e.g., four), and non-number words (e.g., rat) activate semantics in the absence of central attention within the Psychological Refractory Period (PRP) paradigm. In all three experiments, subjects performed colour discriminations as Task 1. In Task 2, subjects performed magnitude comparisons on digits (Experiment 1) and number words (Experiment 2) and size comparisons on animal words (Experiment 3). Task overlap was controlled by varying stimulus onset asynchrony (SOA). A distance effect arose in Task 2 and yielded underadditive effects with decreasing SOA for both digits and number words, consistent with these notations activating semantics in the absence of central attention, or automatically. A distance effect also arose for animal words, but it was additive with SOA, inconsistent with non-number words activating semantics automatically. Author Keywords: Automaticity, Central attention, Dual-task, Numerical cognition, Semantics, Word recognition
To Sext or Not to Sext
The risks and benefits of sexting within an intimate relationship were explored. The present study focused on sexual gratification, relationship benefits, and sexual communication as benefits and risky sexual behaviour, unethical forwarding, and infidelity as risks. A cross-sectional online survey of both undergraduate students and a community sample was used. Results indicated that sexual gratification, relationship benefits (sexual and relationship satisfaction, relationship quality, and commitment), and sexual communication are related to sexting. It appears that risky sexual behaviour is not associated with sexting, instead those who sext frequently engage in more safer sex behaviours than those who sext infrequently. Unethical forwarding does not appear to happen very often in the context of intimate relationships. Lastly, the current research indicates that some participants are sexting secondary partners, and many consider sexting secondary partners infidelity. These results show that there are both risks and benefits of sexting, which can be used to develop sext education and therapeutic programs. Author Keywords: infidelity, relationship benefits, Sexting, sexual behaviour, sexual communication, sexual gratification
Perceive Me, Perceive You
The use of threats to feelings of intimacy and belonging, also known as relational aggression, has been previously explained using attachment representations and attributions in childhood. However, the combined role of attachment representations and attributions in explaining relational aggression in adult peer and romantic relationships has been unexplored. This study tested the associations between attachment, attributions, and relational aggression with a specific focus on the mediating role of attributions. A final sample of 258 undergraduate university students completed self-report surveys and vignettes to measure the variables of interest. Results suggested that attachment predicted relational aggression but, with one exception, attributions did not explain unique variance in relational aggression after controlling for attachment. Interestingly, hostile attributions mediated the relationship between dismissing attachment to romantic partners and romantic relational aggression. Therefore, individuals‘ attachment representations directly influenced their levels of relational aggression in relationships regardless of their attributions. Author Keywords: Adulthood, Attachment, Attributions, Mediation, Relational Aggression
What’s the trouble with women? Fostering female engagement in substance abuse programming
Although Canada’s healthcare system is designed for everyone to access services regardless of the person’s gender, age, or income, there are significant barriers for individuals accessing substance abuse services that live in areas outside of urban centres (Adbool, et al., 2017; Hardill, 2011). Women are particularly stigmatized by the lack of anonymity in smaller communities and often avoid engaging in substance abuse programs (Ashley, Marsden, & Thomas, 2003). The aim of the current thesis was to explore RedPath, a grassroots initiative in Port Hope, Ontario, geared to engaging individuals and encourage them to participate in substance abuse programming. This initiative employs a member from the community, called an Activator, who is tasked with engaging their peers. A qualitative study was conducted to explore the role of a hired RedPath Activator in facilitating access of female community members with substance abuse issues to services in the Port Hope community. Her role in supporting women was a specific interest, as the selection of a female Activator was a strategy to support the engagement of women to the program. The data was analyzed using a thematic content analysis approach. The most significant of these themes were (1) barriers and challenges in the community and (2) building trust to facilitate engagement and maintain attendance in the program. Author Keywords: activator, community, mental health, substance abuse, woman, women
Balance is key
While preferences for symmetry are seemingly universal, they can be seen at their most extreme among individuals high in trait incompleteness. As yet, it is unclear why incompleteness yields heightened symmetry preferences. Summerfeldt et al. (2015) speculated that individuals high in incompleteness may develop heightened preferences for symmetry due to its greater perceptual fluency. Accordingly, the aim of the present set of three experiments was to examine this relationship. Implicit preferences for symmetry were measured using a modified version of the Implicit Association Test (IAT) reported by Makin et al. (2012). Experiments 1 (N = 24) and 2 (N = 24) examined whether the general implicit preferences for symmetry and influence of perceptual fluency reported by Makin et al. (2012) extended to a within-subjects design. Experiment 3 (N = 86) examined whether trait incompleteness is related to greater implicit preferences for symmetric stimuli, and whether perceptual fluency affects this association. Results showed that incompleteness and implicit preferences were related, and that incompleteness-related differences in preferences were eliminated when the patterns were equally perceptually fluent, supporting the idea that incompleteness-related preferences for symmetry are linked to perceptual fluency. Implications of these findings are discussed. Author Keywords:
Assessing Emotion Processing Deficits in Youth
It is well-established that alexithymia in adulthood is a critical risk factor for numerous negative mental health and well-being outcomes. Although this area of research has begun to receive interest in earlier developmental stages, significant methodological limitations have been noted with current measures of alexithymia for adolescence. As such, the aim of the current thesis was to provide empirical evidence on the psychometric strength of a new adolescent measure of alexithymia, the Toronto Alexithymia Scale – Adolescent Version (TAS-A). Study 1 examined the construct validity of the TAS-A in relation to self and informant reported emotional intelligence (EI), while study 2 examined the predictive validity of the TAS-A in relation to adolescent problematic gambling and academic achievement. Adolescents completed self-reports of alexithymia, EI, and gambling behaviour, parents completed informant reports regarding their child’s EI, and academic records were obtained. Confirmatory factor analyses revealed significant relationships between adolescent alexithymia, and self and informant reported EI, indicating significant overlap in constructs. Adolescent alexithymia was also shown to be a significant predictor of problematic gambling and academic achievement; however, some interesting gender differences were observed (a pattern of results reported consistently in the adult alexithymia literature). Results are discussed in terms of methodological and clinical implications during the vulnerable developmental transition of adolescence. Author Keywords: adolescence, alexithymia, psychometrics
Using a real-world chopping task to study motor learning and memory
Typically task interference is studied using reaching adaptation tasks (visuomotor rotation and/or force-field learning). Participants in these experiments are already experts at the base task (point-to-point, planar reaching) and their ability to adapt reaching to the imposed perturbation is studied. The pattern of data induced by the perturbation is used to make inferences about the nature and neural correlates of our learning and memory for reaching perturbations, specifically, and motor performance in general. We wanted to see if it is possible to demonstrate this same interference pattern using a novel vegetable-chopping task, where we can easily recreate natural performance settings using a task for which we can easily identify non-experts. Participants performed a chopping task in which they are asked to chop a sweet potato into 5 mm-wide slices, matching the beat of a metronome (120 bpm). Following this initial learning, participants were exposed to an interference condition. Participants then performed trials of the original task again. Interference was inferred if the second performance of the original task was impaired, compared to initial performance. Experiment 1 involved novice choppers, and either the force or frequency of chops was manipulated. Only the altered frequency task produced interference effects. In Experiment 2, competent and expert choppers had to manage either a faster or slower frequency. We found evidence for interference in competents, but not experts. These results support the idea that the vulnerability to interference of motor memory changes with practice, and so any inferences made about memory structure must take into account not only expert performance, but every level of skill. Author Keywords: expertise, interference, motor learning, reaching adaptation
Assessing the Clinical Usefulness of Three Tablet-Based Visuomotor Tasks to Evaluate Closed Head Injury
Evidence suggests that visuomotor system behaviour may be more sensitive to the prolonged effects of mild brain injuries than neuropsychological tests. We evaluated whether participants with a mild closed head injury (CHI) would show lingering visuomotor deficits, but not cognitive deficits, up to three years post-injury compared to participants with an orthopaedic injury and healthy controls. All three groups completed a tablet-based visuomotor assessment tool and a brief neuropsychological test battery. The CHI participants scored comparable to the control groups on the neuropsychological tests, but when assessed for visuomotor function requiring adjustment to a changing stimulus, CHI participants showed poorer performance than the control groups. Combined, these findings add to the evidence that CHI can lead to persistent visuomotor deficits that extend beyond those of neuropsychological tests. Therefore, visuomotor assessment should be included in brain injury and recovery evaluation, and this can be accomplished easily using tablet-based tasks. Author Keywords: closed head injury, neuropsychological assessment, recovery, tablet, traumatic brain injury, visuomotor
Context Fear Memory
Distributing contextual fear episodes makes the memory become HPC-independent, meaning increasingly reliant on non-HPC memory structures. It is unclear, however, whether distribution of the conditioning episodes alone is sufficient or whether a combination of distribution and high conditioning saliency is necessary to make the memory become HPC-independent. To resolve this issue, rats were trained using a distributed contextual fear conditioning protocol in which foot-shocks were manipulated to create a low (0.4mA), intermediate (0.7 mA) and high (1.0 mA) saliency condition. This thesis also aimed to determine brain structures supporting the HPC-independent memory by assessing retention-induced c-fos expression in the basolateral- amygdala, perirhinal and anterior cingulate cortices. The results suggest that HPC lesion rats in the high saliency condition displayed similar level of freezing as control rats, indicating “strongly salient” and distributed episodes creates a HPC independent memory. c-fos expression suggests together, an increased context representation in the perirhinal and anterior cingulate cortices and a strengthened fear representation in the basolateral-amygdala supports the HPC-independent memory. Author Keywords: context fear memory, distributed reinstatements, hippocampus, IEG, rat, saliency
Altered Hippocampal Regulation of Immediate Early Genes after Pentylenetetrazol-Induced Seizures
Seizures induce long-term changes in gene expression in the hippocampus. Experimental evidence has demonstrated a significant effect of epileptic activity on the activity of neurons that participate in complex cognitive and behavioural processes. The present series of experiments involving kindling with subconvulsive doses of PTZ demonstrates a link between seizures and altered immediate early gene expression within the hippocampus and dentate gyrus. In addition, newborn hippocampal neurons were shown to have decreased induction of plasticity-related genes, suggesting deficits in activity-dependent recruitment. These findings may shed light on the mechanisms underlying epileptogenesis and epilepsy-related hippocampal dysfunction in human patients. Author Keywords: hippocampus, IEGs, kindling, neurogenesis, seizures


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