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Major depressive disorder is a devastating disease characterized by intense and prolonged sadness and feelings of hopelessness and worthlessness. While developments in drug therapy have provided some insight into the mechanisms underlying depression, investigations employing animal models have provided another strategy for studying the neurobiology of depression. The first generation of these models evolved to evaluate the therapeutic potential of novel drugs, and included the reserpine reversal test, forced swimming test, and the brain-stimulation reward (BSR) procedure. The rationale in the case of the latter was that since one of the core symptoms of depression is a decreased capacity to experience pleasure, interventions that relieve these symptoms in humans will enhance reward transmission; in animals, this was interpreted from decreases in thresholds for BSR. In the first experiment, we evaluated the effects of paroxetine, an antidepressant of the selective serotonin reuptake inhibitor class, on BSR thresholds and observed only modest decreases in thresholds. These results mimicked the minimal mood altering effects that antidepressants are reported to have in "normal" individuals. Next, as a means of inducing a depressive state in rats, the chronic mild stress (CMS) procedure, developed to model anhedonia, a core symptom of depression, was employed in the subsequent experiments. Its consequences were measured on several indices of depressive behaviours, sucrose consumption (1 and 24h intake and preference), BSR thresholds, and the forced swim test. Genetic variation was considered by comparing male and female rats of two outbred strains. While CMS produced little change in BSR thresholds, its effects on sucrose consumption were varied; in male rats, we observed an initial reduction in 1h sucrose intake in Long Evans exclusively, while a CMS-induced reduction on the 24h intake measure was evident in both strains of female rats, with a greater effect in the Sprague-Dawley group. In evaluating the effects of CMS on forced swimming behaviour, we saw no group or strain difference in the female rats and a notable strain difference in male rats. Long Evans animals with a history of stress significantly reduced the duration of the test engaged in escape-type behaviours on the second exposure to forced swim, as would be expected in animals experiencing learned helplessness, a behaviour characteristic of depressed individuals. (Abstract shortened by UMI.)

The perception of an event as being potentially harmful or stressful to the individual sets off a cascade of responses, including the activation of neurons located in the hypothalamus. Despite the extensive efforts in understanding the various neurochemical systems regulating this cascade of events, many questions remain unanswered concerning the underlying mechanisms involved. Evidence from our laboratory suggests involvement of bombesin (BB; a peptide of amphibian origin), in the mediation and/or modulation of the stress response. Two BB-like peptides have been identified in mammals, gastrin-releasing peptide (GRP) and neuromedin B (NMB). Experimental evidence acquired thus far seems to suggest the potential involvement of BB-like peptides in the mediation of the stress response as well as other related responses, such as fear and anxiety. However, very few experiments have focused on determining the specific roles of NMB and GRP in mechanisms underlying the integration of stress and/or anxiety responses. Thus, the overall objective of this thesis is to clarify the intrinsic role of each of these peptides in the hope of gaining a better understanding of the underlying mechanisms mediating stress-related responses. This extensive research project provides new evidence suggesting that both endogenous BB-like peptide systems, GRP and NMB, are significantly involved in the modulation/facilitation of stress-, anxiety- and/or fear-related behaviors. Their intrinsic roles appear to be different; whereas NMB seems to mediate both anxiety and fear, GRP seems to selectively alter more robust stress-related behaviors, such as fear. This thesis project provides important additional support for the involvement of this family of peptides in stress related responses. It also provides interesting insight into the different mechanism(s) of action that might underlie stress, anxiety and/or fear. This new evidence should help in the development of more specific, and therefore efficient, therapeutic agents in the prevention and treatment of stress-related disorders.

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The purpose of this study was to explore how asking for general music preferences compares to asking for music preferences that relate to the intended objective (in this case, relaxation), and to determine if one of these types of preferred music was more effective than the other in eliciting relaxation. Participants, who were undergraduate non-music majors (N = 71), took part in a music listening study in which their perceived relaxation and galvanic skin response (GSR) levels were recorded. Participants were placed in one of three groups: the participant-selected preferred music group (PM), the participant-selected preferred relaxing music group (PRM), or the unfamiliar, non-preferred music group (NPM). Results indicate that participants in the PM and PRM groups experienced significant increases in perceived relaxation and significant decreases in GSR levels, but there was not a significant difference between the two groups in the amount of change. Therefore, preferred music and preferred relaxing music appear equally effective in increasing relaxation responses. These findings provide support for the continued use of patient-preferred music in music therapy settings and offer alternative suggestions for assessing music preferences. / A Thesis submitted to the College of Music in partial fulfillment of the requirements for the degree of Master of Music. / Summer Semester 2015. / July 13, 2015. / galvanic skin response, music preference, music therapy, relaxation / Includes bibliographical references. / John Geringer, Professor Directing Thesis; Jayne M. Standley, Committee Member; Dianne Gregory, Committee Member.

The current studies focus on individual difference predictors of the phenomenon inattentional blindness (IB; when observers fail to notice a salient but unexpected event when attention is occupied by another task). Study 1 (conducted on Mechanical Turk) explicitly examined unexpected object salience as the moderator between the potential relationship between working memory capacity and IB. Salience was varied in two ways: 1) the color of the unexpected item (gray vs. red) and also the distance of the unexpected item from fovea (near vs. far). A second lab-based study explored the degree to which attentional control is an important individual difference predictor of IB, with the idea that individuals more susceptible to attention capture will be more likely to notice the unexpected event, and individuals who are better able to filter irrelevant information will miss it more. Study 2 tested this hypothesis by examining the relationship between four classic measures of attentional control (measuring implicit capture of attention using reaction time) and IB (measuring explicit detection of an unexpected object using participant report). Contrary to hypotheses, working memory capacity was not a significant predictor of IB, even in instances in which the unexpected object was highly salient (Study 1). Moreover, Study 2 found no relationship between classic measures of implicit capture (based on RT) and explicit capture (participant report of noticing an unexpected event). Instead, age, processing speed, and conscientiousness demonstrated predictive ability in distinguishing noticers and non-noticers. Results suggest that attentional control (measured via working memory capacity or classic measures of attention capture) is unrelated to explicit detection of an unexpected stimulus. / A Dissertation submitted to the Department of Psychology in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Summer Semester 2015. / July 17, 2015. / Attentional Control, Attention Capture, Distraction, Inattentional Blindness, Selective Attention, Working Memory / Includes bibliographical references. / Walter Boot, Professor Directing Dissertation; Betsy Becker, University Representative; Neil Charness, Committee Member; Jonathan Folstein, Committee Member; Arielle Borovsky, Committee Member.

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