Fournier, Neil

Stress can significantly affect neurobiological processes crucial for learning and memory. While repeated stress enhances fear memory, it impairs memory retrieval. In most studies, however, stress exposure typically preceded fear and extinction learning. Thus, the impact of previously acquired memories formed before exposure to stress is not well understood. The goal of this thesis is to examine how acute stress impacts the ability to retrieve previously acquired fear memories. The results showed that stress impaired recall of recent fear memories, but stress seven days after conditioning did not affect memory retrieval. Analysis of c-Fos expression revealed increased neuronal activity in the medial prefrontal cortex (mPFC) of rats exposed to stress. Additionally, stress exposure decreased mRNA expression of Reelin, a glycoprotein in the mPFC. Notably, administering recombinant Reelin improved fear memory recall. These findings highlight potential pathways for research and interventions on stress-induced memory impairments.

Author Keywords: c-Fos expression, Fear memory, Medial prefrontal cortex, Memory retrieval, Reelin, Stress

Freezing is a debilitating phenomenon that reduces quality of life for people withParkinson's disease (PwPD). This study tests the hypothesis that: 1) freezing is linked to executive dysfunction; 2) freezing is a global motor phenomenon, not limited to gait. We compared 14 PwPD to 16 controls. Several aspects of executive function were measured using pro- and anti-saccade tasks under gap and overlap timing conditions, where the gap effect is defined as the reduction in saccade latency associated with the removal of fixation before target presentation. As predicted, results showed larger anti-saccade gap effects in PwPD with than without FOG, and that the pro-saccade gap effect predicted FOG severity in PwPD with FOG. PwPD also demonstrated impaired performance on reaching and walking tasks designed to elicit freezing. These findings strengthen the evidence that executive dysfunction, measured by saccade tasks, is linked to freezing in PwPD.

Author Keywords: executive function, eye movements, freezing of gait, freezing of upper limbs, Parkinson's disease

Stress during adolescence has profound effects on psychological, behavioral, and neurobiological outcomes in adulthood. This study investigates the impact of adolescent stress on safety learning, anxiety- and depressive-like behaviors, and associated neurocircuitry using a rat model. Adolescent male Long Evans rats underwent an unpredictable intermittent stress regimen, followed by behavioral testing and immunohistological analyses in adulthood. It was confirmed that stress impaired safety learning and increased fear generalization. Behavioral assays revealed heightened anxiety- and depressive-like phenotypes in stressed rats, evidenced by reduced open-arm exploration in the elevated plus maze and increased immobility in the forced swim test, although limited changes in sucrose preference were noted during habituation. Immunohistological findings showed reductions in hippocampal neurogenesis (DCX+ cells) and disruptions in GABAergic interneuron plasticity (PV+/PNN+ populations) within the medial prefrontal cortex. These alterations suggest that adolescent stress leads to long-term changes in brain regions associated with emotional regulation and stress resilience.

Author Keywords: Adolescencent Stress, Anxiety-like Behaviour, Hippocampus, Medial Prefrontal Cortex, Neuroplasticity, Safety Learning

Recently, equine assisted learning (EAL) has emerged as a novel approach to building resiliency competencies in at-risk youth. This mixed-methods study presents evaluation results for an 8-week community-based EAL program with 83 young women (age 13-18 years) with a history of interpersonal trauma. Analyses examined changes in self-reported mental health symptoms (posttraumatic, depression) and resiliency factors (sense of mastery, sense of relatedness, emotion regulation) from pre- to post-test and at 1-month and 6-month follow-ups. Changes in outcomes were also correlated with intervention processes (attendance, session ratings) to see if program experiences were associated with differential outcomes. Results showed that EAL has potential in improving resiliency outcomes, at least for those participants who derived greater satisfaction and value from the sessions. Many improvements were sustained over the long term. Participants' qualitative feedback provided insight into their subjective experiences and highlighted the unique role that horses played in the EAL process.

Author Keywords: Emotion Regulation, Equine Assisted Learning, Experiential Learning, Resilience, Sense of Mastery, Sense of Relatedness

Academic procrastination is analogous to a common cold: pervasive and with no established cure. Students experience repercussions that are not inclusive to academic performance, but rather, are experienced across mental, physical, social and emotional domains as well. While this necessitates treatment, much of the behaviour has yet to be explained. In the current study, a state approach was integrated to explore procrastination in terms of the Yerkes-Dodson paradigm. Procrastination was hypothesized to arise for one of two reasons: students are either too low or too high in anxiety. A sample of 847 Ontario undergraduate students completed measures of procrastination, state-anxiety, personality, and self-regulation. Results suggest 88% of students procrastinate regularly, and contrary to what was hypothesized, procrastination and anxiety were linearly related. Independent t-tests establish that relative to non-procrastinators, procrastinators are significantly more emotionally and biologically dysregulated and less socially integrated. Factor analysis demonstrated three central reasons contributing to procrastination, which were used as the basis to establish types of procrastination: social (n=61), self-doubt (n=70) and low-energy (n=76) procrastinators. Results indicate divergences across procrastination type with respect to personality as well as biological, affective and social domains. Findings also inform that the expression of procrastination, varies across student. Overall, findings suggest that academic interventions should acknowledge and address the variability among procrastinators.

Author Keywords: ACADEMIC PROCRASTINATION, ANXIETY, PERSONALITY, SELF-REGULATION

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