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Food is an essential driver of animal behavior. For social organisms, the acquisition of food guides interactions with the environment and with group-mates. Studies have focused on how social individuals find and choose food sources, and share both food and information with group-mates. However, it is often not clear how

Food is an essential driver of animal behavior. For social organisms, the acquisition of food guides interactions with the environment and with group-mates. Studies have focused on how social individuals find and choose food sources, and share both food and information with group-mates. However, it is often not clear how experiences throughout an individual's life influence such interactions. The core question of this thesis is how individuals’ experience contributes to within-caste behavioral variation in a social group. I investigate the effects of individual history, including physical injury and food-related experience, on individuals' social food sharing behavior, responses to food-related stimuli, and the associated neural biogenic amine signaling pathways. I use the eusocial honey bee (Apis mellifera) system, one in which individuals exhibit a high degree of plasticity in responses to environmental stimuli and there is a richness of communicatory pathways for food-related information. Foraging exposes honey bees to aversive experiences such as predation, con-specific competition, and environmental toxins. I show that foraging experience changes individuals' response thresholds to sucrose, a main component of adults’ diets, depending on whether foraging conditions are benign or aversive. Bodily injury is demonstrated to reduce individuals' appetitive responses to new, potentially food-predictive odors. Aversive conditions also impact an individual's social food sharing behavior; mouth-to-mouse trophallaxis with particular groupmates is modulated by aversive foraging conditions both for foragers who directly experienced these conditions and non-foragers who were influenced via social contact with foragers. Although the mechanisms underlying these behavioral changes have yet to be resolved, my results implicate biogenic amine signaling pathways as a potential component. Serotonin and octopamine concentrations are shown to undergo long-term change due to distinct foraging experiences. My work serves to highlight the malleability of a social individual's food-related behavior, suggesting that environmental conditions shape how individuals respond to food and share information with group-mates. This thesis contributes to a deeper understanding of inter-individual variation in animal behavior.
ContributorsFinkelstein, Abigail (Author) / Amdam, Gro V (Thesis advisor) / Conrad, Cheryl (Committee member) / Smith, Brian (Committee member) / Neisewander, Janet (Committee member) / Bimonte-Nelson, Heather A. (Committee member) / Arizona State University (Publisher)
Created2017
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Description
Aging and the menopause transition are both intricately linked to cognitive changes

during mid-life and beyond. Clinical literature suggests the age at menopause onset can differentially impact cognitive status later in life. Yet, little is known about the relationship between behavioral and brain changes that occur during the transitional stage into

Aging and the menopause transition are both intricately linked to cognitive changes

during mid-life and beyond. Clinical literature suggests the age at menopause onset can differentially impact cognitive status later in life. Yet, little is known about the relationship between behavioral and brain changes that occur during the transitional stage into the post-menopausal state. Much of the pre-clinical work evaluating an animal model of menopause involves ovariectomy in rodents; however, ovariectomy results in an abrupt loss of circulating hormones and ovarian tissue, limiting the ability to evaluate gradual follicular depletion. The 4-vinylcyclohexene diepoxide (VCD) model simulates transitional menopause in rodents by selectively depleting the immature ovarian follicle reserve and allowing animals to retain their follicle-deplete ovarian tissue, resulting in a profile similar to the majority of menopausal women. Here, Vehicle or VCD treatment was administered to ovary-intact adult and middle-aged Fischer-344 rats to assess the cognitive effects of transitional menopause via VCD-induced follicular depletion over time, as well as to understand potential interactions with age, with VCD treatment beginning at either six or twelve months of age. Results indicated that subjects that experience menopause onset at a younger age had impaired spatial working memory early in the transition to a follicle-deplete state. Moreover, in the mid- and post- menopause time points, VCD-induced follicular depletion amplified an age effect, whereby Middle-Aged VCD-treated animals had poorer spatial working and reference memory performance than Young VCD-treated animals. Correlations suggested that in middle age, animals with higher circulating estrogen levels tended to perform better on spatial memory tasks. Overall, these findings suggest that the age at menopause onset is a critical parameter to consider when evaluating learning and memory across the transition to reproductive senescence. From a translational perspective, this study informs the field with respect to how the age at menopause onset might impact cognition in menopausal women, as well as provides insight into time points to explore for the window of opportunity for hormone therapy during the menopause transition to attenuate age- and menopause- related cognitive decline, and produce healthy brain aging profiles in women who retain their ovaries throughout the lifespan.
ContributorsKoebele, Stephanie Victoria (Author) / Bimonte-Nelson, Heather A. (Thesis advisor) / Aiken, Leona S. (Committee member) / Conrad, Cheryl D. (Committee member) / Wynne, Clive DL (Committee member) / Arizona State University (Publisher)
Created2015
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Description

In females, critical hormonal shifts occur during puberty, menstruation, pregnancy, and <br/>menopause. The fluctuating ovarian hormone levels across a woman’s lifespan likely contribute <br/>to inflammatory responses driven by the immune system, which is regulated by a variety of <br/>physiological pathways and microbiological cues. Pregnancy in particular results in drastic <br/>changes

In females, critical hormonal shifts occur during puberty, menstruation, pregnancy, and <br/>menopause. The fluctuating ovarian hormone levels across a woman’s lifespan likely contribute <br/>to inflammatory responses driven by the immune system, which is regulated by a variety of <br/>physiological pathways and microbiological cues. Pregnancy in particular results in drastic <br/>changes in circulating hormone profiles, and involves a variety of physiological changes, <br/>including inflammatory responses of the immune system. There is evidence that these effects are <br/>mediated, in part, by the significant hormone fluctuations that characterize pregnancy and <br/>postpartum periods. This thesis highlights and synthesizes important physiological changes <br/>associated with pregnancy, and their potential implications on cognitive and brain aging in <br/>women. A tertiary model of cognition is presented depicting interactions between hormonal <br/>history, reproductive history, and immune functions. This research is important to create a better <br/>understanding of women’s health and enhance medical care for women throughout pregnancy <br/>and across reproductive hormone shifts across the lifespan.

ContributorsLogan-Robledo, Santiago Rodrigo (Author) / Bimonte-Nelson, Heather A. (Thesis director) / Koebele, Stephanie V. (Committee member) / Simard, Alain (Committee member) / School of Life Sciences (Contributor) / Department of Psychology (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
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Description

The relevance of depression in the clinical realm is well known, as it is one of the most common mental disorders in the United States. Clinical depression is the leading cause of disease for women worldwide. The sex difference in depression and anxiety has guided the research of not just

The relevance of depression in the clinical realm is well known, as it is one of the most common mental disorders in the United States. Clinical depression is the leading cause of disease for women worldwide. The sex difference in depression and anxiety has guided the research of not just recent studies but older studies as well, supporting the theory that gonadal hormones are associated with the mechanisms of emotional cognition. The scientific literature points towards a clear correlative relationship between gonadal hormones, especially estrogens, and emotion regulation. This thesis investigates the neural pathways that have been indicated to regulate mood and anxiety. Currently, the research points to the hypothalamic-pituitary-adrenal axis, which regulates the stress response through its ultimate secretion of cortisol through the adrenal cortex, and its modulated response when exposed to higher levels of estrogen. Another mechanism that has been investigated is the interaction of estrogen and the serotonergic system, which is noteworthy because the serotonergic system is known for its importance in mood regulation. However, it is important to note that the research seeking to determine the neurobiological underpinnings of estrogen and the serotonergic system is not expansive. Future research should focus on determining the direct relationship between cortisol hypersecretion and estrogens, the specific neurobiological effects of serotonergic receptor subtypes on the antidepressant actions of estrogens, and the simultaneous effects of the stress and serotonergic systems on depressive symptoms.

ContributorsArroyo, Mariana (Author) / Bimonte-Nelson, Heather (Thesis director) / Jurutka, Peter (Committee member) / School of International Letters and Cultures (Contributor) / School of Social and Behavioral Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
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Description
Progestogens, such as progesterone (P4), medroxyprogesterone acetate (MPA), and micronized progesterone (mP4), are given to ovary-intact women during the transition to menopause to attenuate heavy uterine bleeding and other symptoms. Both progesterone and MPA administration have been shown to impair cognition in ovariectomized (Ovx) rats compared to vehicle-treated controls. mP4,

Progestogens, such as progesterone (P4), medroxyprogesterone acetate (MPA), and micronized progesterone (mP4), are given to ovary-intact women during the transition to menopause to attenuate heavy uterine bleeding and other symptoms. Both progesterone and MPA administration have been shown to impair cognition in ovariectomized (Ovx) rats compared to vehicle-treated controls. mP4, however, has yet to be investigated for cognitive effects in a preclinical setting. Further, progestogens affect the GABA (-aminobutyric acid) ergic system, specifically glutamic acid decarboxylase (GAD) the rate limiting enzyme necessary for synthesizing GABA. The goal of this experiment was to investigate the cognitive impact of P4, MPA, and mP4, in an ovary-intact transitional menopause model using 4-vinylcyclohexene diepoxide (VCD) and assess whether these potential changes were related to the GABAergic system. One group of rats received vehicle injections, and the remainder of the groups received VCD to induce follicular depletion, modeling transitional menopause in women. Vehicle or hormone administration began during perimenopause to model the time period when women often take progestogens alone. Rats then underwent testing to assess spatial working and reference memory in the water radial-arm maze (WRAM) and spatial reference memory in the Morris water maze (MWM). Results indicate that P4 and MPA improved learning for working memory measure, but only MPA impaired memory retention in the WRAM. For the WRAM reference memory measure, VCD only treated rats showed impaired learning and memory retention compared to vehicle controls; progestogens did not impact this impairment. Although GAD expression did not differ between treatment groups, in general, there was a relationship between GAD expression and WRAM performance such that rats that tended to have higher GAD levels also tended to make more WRAM working memory errors. Thus, while P4 and MPA have been previously shown to impair cognition in an Ovx model, giving these hormones early in an ovary-intact perimenopause model elicits divergent effects, such that these progestogens can improve cognition. Additionally, these findings suggest that the cognitive changes seen herein are related to the interaction between progestogens and the GABAergic system. Further investigation into progestogens is warranted to fully understand their impact on cognition given the importance of utilizing progestogens in the clinic.
ContributorsPena, Veronica Leigh (Author) / Bimonte-Nelson, Heather A. (Thesis advisor) / Conrad, Cheryl (Committee member) / Gipson-Reichardt, Cassandra (Committee member) / Arizona State University (Publisher)
Created2019
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Description
Reproductive hormones are recognized for their diverse functions beyond reproduction itself, including a vital role in brain organization, structure, and function throughout the lifespan. From puberty to reproductive senescence, the female is characterized by inherent responsiveness to hormonal cyclicity. For most women, a natural transition to menopause occurs in midlife,

Reproductive hormones are recognized for their diverse functions beyond reproduction itself, including a vital role in brain organization, structure, and function throughout the lifespan. From puberty to reproductive senescence, the female is characterized by inherent responsiveness to hormonal cyclicity. For most women, a natural transition to menopause occurs in midlife, wherein the endogenous hormonal milieu undergoes significant changes and marks the end of the reproductive life stage. Although most women experience natural menopause, many women will undergo gynecological surgery during their lifetime, which can lead to an abrupt surgical menopause. It is of critical importance to better understand how endogenous and exogenous reproductive hormone exposures across the lifespan influence cognitive and brain aging, as women are at a greater risk for developing a variety of diseases after menopause, including dementia. Using rodent models, this dissertation explores how the etiology of reproductive senescence, that is, whether it is transitional or surgical, influences the female phenotype to result in divergent cognitive outcomes dependent upon a variety of factors, with an emphasis on age at the time of intervention playing a key role in brain outcomes. Furthermore, the impact of exogenous hormone therapy on cognition is evaluated in the context of surgical menopause. A novel rat model of hysterectomy is also presented, with results demonstrating for the first time that the nonpregnant uterus, which is typically considered to be a quiescent organ, may play a unique, direct role in modulating cognitive outcomes. Neurobiological mechanisms associated with reproductive hormones and aging are assessed to better recognize neural correlates underlying the observed behavior changes. The overarching goal of this dissertation was to elucidate novel factors contributing to cognitive aging outcomes in females. Collectively, the data presented herein indicate that the age at the onset of reproductive senescence has significant implications for learning and memory outcomes, and that variations in gynecological surgery can have unique, long-lasting effects on the brain and cognition. Translationally, this series of experiments moves the field forward toward the goal of improving the health and quality of life for women throughout the lifespan.
ContributorsKoebele, Stephanie Victoria (Author) / Bimonte-Nelson, Heather A. (Thesis advisor) / Conrad, Cheryl D. (Committee member) / DeNardo, Dale F (Committee member) / Newbern, Jason M (Committee member) / Reiman, Eric M (Committee member) / Arizona State University (Publisher)
Created2019