Cholecystokinin (CCK) causes panic attacks in humans and increases fear-associated behaviours in rodents by way of CCK-B receptors. The aim of this thesis was to investigate the CCK system behaviourally and anatomically in C57BL6/J mice and to assess the suitability of CCK-IRES-Cre mouse lines for amygdala manipulation. The behavioural results failed to support the startle-activating effect of CCK-4 or the startle-inhibiting effects of CCK-B receptor antagonists, in spite of evidence showing CCK-4 induced activation of c-Fos in the central amygdala. The anatomical results show that CCK-8 expression in the basolateral amygdala (BLA) is comparable to the CCK mRNA expression pattern. These results suggest that viral manipulations in the CCK-IRES-Cre line will induce changes in endogenous CCK systems in the mouse amygdala.

Cholecystokinin (CCK) causes panic attacks in humans and increases fear-associated behaviours in rodents by way of CCK-B receptors. The aim of this thesis was to investigate the CCK system behaviourally and anatomically in C57BL6/J mice and to assess the suitability of CCK-IRES-Cre mouse lines for amygdala manipulation. The behavioural results failed to support the startle-activating effect of CCK-4 or the startle-inhibiting effects of CCK-B receptor antagonists, in spite of evidence showing CCK-4 induced activation of c-Fos in the central amygdala. The anatomical results show that CCK-8 expression in the basolateral amygdala (BLA) is comparable to the CCK mRNA expression pattern. These results suggest that viral manipulations in the CCK-IRES-Cre line will induce changes in endogenous CCK systems in the mouse amygdala.

Thesis (Ph. D.)--Dept. of Psychology. University of Missouri--Kansas City, 2005. / "A dissertation in psychology." Advisor: Diane L. Filion. Typescript. Vita. Title from "catalog record" of the print edition Description based on contents viewed March 12, 2007. Includes bibliographical references (leaves 115-120). Online version of the print edition.

Ecological context, sensory inputs, and the internal physiological state are integrated for an animal to make appropriate behavioral decisions. However, these factors have rarely been studied in the same system. In the African cichlid fish Astatotilapia burtoni, males alternate between four phenotypes. Two are determined by social status and two are identified by the principle body coloration (yellow or blue). When socially dominant (DOM), fish display bright body coloration and a wealth of aggressive and reproductive behaviors. Subordinate (SUB) males decrease predation risk by adopting cryptic coloration and schooling behavior. Yellow males are more conspicuous than blue males, and DOMs and more conspicuous than SUBs, which means that yellow DOMs are most likely to be seen by predators. We therefore hypothesized that DOMs, yellow DOMs in particular, would show enhanced startle-escape responsiveness to compensate for their increased predation risk. Indeed, behavioral responses to sound clicks of various intensities showed a significantly higher mean startle rate in DOMs than SUBs. When testing the same males after social change, yellow DOMs respond at a higher rate than yellow SUBs but blue males do not show plasticity. Electrophysiological recordings from the Mauthner cells (Mcells), the neurons triggering startle, were performed in anesthetized animals and showed larger synaptic responses to sound clicks in DOMs, consistent with the behavioral results. In addition, the inhibitory drive mediated by interneurons presynaptic to the M-cell was significantly reduced in DOMs. Using behavioral tests, intracellular recordings, and single-cell molecular analysis, immunohistochemistry and in-situ hybridization, I show here that serotonin modulates this socially regulated plasticity via the 5-HT receptor subtype 2 (HTR2A). Specifically, SUBs display increased sensitivity to pharmacological blockade of HTR2A compared with DOMs in both startle-escape behavior and electrophysiological properties of the M-cell. These receptors, however, are not expressed in the Mauthner neurons, but in the inhibitory interneurons that regulate the Mcell’s membrane properties. I show a role for 5-HT in modulating startle plasticity and increase our understanding of the neural basis of behavioral plasticity. More broadly, this study provides an integrative explanation of an ecological and social trade-off at the level of an identifiable decision-making neural circuit. / text

Thesis (Ph.D.) - University of Queensland, 2005. / Includes bibliography.

High-hostiles exhibit exaggerated physiological responses to stressors as seen by increased cardiovascular reactivity (BP & HR) (Rhodes, Harrison, & Demaree, 2002; Demaree & Harrison, 1997). This exaggerated physiological response style is associated with cardiovascular disease and premature death (Everson et al., 1997). This experiment hypothesized that diminished regulatory control would also be evident in the Acoustic Startle Response (ASR). In this experiment, high- and low-hostile undergraduate men (N = 40) were exposed to a series of startle probes before and after a cold pressor (CP). Startle responses were measured using electromyography (EMG) recorded over the orbicularis occuli. Cardiovascular measures of blood pressure and heart rate were also taken. A 2 X 2 mixed factorial ANOVA was performed with Group (high and low hostile) as the fixed factor, Condition (pre and post CP) as the repeated measure, and peak magnitude EMG (mV) of startle responses as the dependent variable. For startle responses, significant main effects for Group and Condition indicated that high hostiles had larger startle responses than low hostiles and startle responses decreased after the cold pressor (CP). A significant Group X Condition interaction effect was found. Post-hoc analyses revealed no significant group differences before the CP. After the CP, high-hostiles had significantly higher startle responses than-low hostiles. High-hostiles' startle responses did not change significantly after the CP, whereas low-hostiles' startle response magnitude decreased significantly after the CP. Low-hostiles HR increased significantly after the cold pressor and both groups SBP decreased significantly after the cold pressor. / Master of Science

Defence sounds are widespread and diverse amongst insects. Despite their ubiquity and variability, hypotheses explaining their functions and evolutionary origins have been understudied. My thesis focused on these topics using silk and hawkmoth Bombycoidea caterpillars as a model system. In Chapter Two I investigated why defence sounds have evolved in some caterpillars but not others by testing the hypothesis that large body size is a factor in the evolution of defence sounds. To test this hypothesis, I followed the development of defence sounds in four Bombycoidea species from hatching to pupation. I predicted that early instars would not produce defence sounds, and that within sound producing instars defence sounds would be more likely to occur in larger caterpillars. Results showed that defence sounds were absent in the first and second instar, and that they developed in the third through to the fifth instar in all species. Moreover, the onset of sound production occurred when all species were the same relative size (~1.12 g, ~26.37 mm), despite the fact that the species differed in their final instar size. I concluded that early instar caterpillars do not make defence sounds, and that there is a critical size when defence sounds develop. I further tested the hypothesis that smaller caterpillars do not have enough energy to make defence sounds, by analyzing the relationship between size and several temporal characteristics of the sounds. I predicted that smaller caterpillars would signal less than larger caterpillars, and produce shorter signal units and trains, with lower duty cycles. Results partly supported the hypothesis, showing that in two species there was a positive relationship between size and the number of units produced within two seconds following an attack, the mean number of units per train, and the mean duration of the units in one species. I also tested the hypothesis that sounds of small caterpillars are not in the hearing range of predators. I predicted that there would be a relationship between caterpillar size, and the sound pressure levels and dominant frequencies of the sounds. Results showed no significant relationships with dominant frequencies or sound pressure levels and size. I concluded that the caterpillars made sounds that were within the hearing range of major predators from the onset of sound production. In Chapter Three I followed the other antipredator defences of the four species throughout development. I investigated whether the frequency of defences changed with instar. I found that the caterpillars employed up to seven different secondary defences throughout development. In one species the frequency of dropping and major thrashing increased in the late instars, and in a different species the frequency of regurgitation increased. I concluded that in some cases defence sound production accompanies other secondary defences that increase with the size of caterpillars during development. In Chapter Four I tested the hypothesis that the defensive whistle of the walnut sphinx caterpillar, Amorpha juglandis (Sphingidae: Sphinginae), functions to startle birds. I predicted that the birds would startle to the sounds, and habituate upon repeated exposure within a trial. Results showed that play-back recordings of the whistles elicited a startle response in captive red-winged blackbirds (Agelaius phoeniceus) and caused them to hesitate and/or flee from prey. I concluded that the whistles function as a startle display. Together, the experiments conducted within my thesis addressed important outstanding questions regarding the evolutionary origins of defence sounds in caterpillars, and their functions in predator-prey interactions.

This thesis reports on research examining the habituation of emotional variables to filmed violence. The following subjective emotional variables were assessed: positive feelings, anxiety, disgust, entertainment and anger. In addition, an objective measure of emotional response was recorded physiologically, using the startle eyeblink response. The mediating influence of personality, individual differences and contextual features on an individuals’ perception of and reaction to filmed violence were also explored. Study one was exploratory in nature served to identify and select the film stimuli to be employed in the subsequent studies. The primary aim of the study was to allow for the identification of violent stimuli considered to be most socially and culturally relevant. The present research builds on existing scientific literature which has began to appreciate that differences in the context of a portrayal holds important implications for its impact on viewers. Thus, a secondary and more specific desire of study one was to obtain an evaluation of the contextual features of the violent film segments. A sample of 30 participants viewed and rated the film stimuli on the variables of realism, fantasy and violence. From this exploratory study four violent film stimuli were subsequently employed. Study 2 used the eyeblink startle response proposed by Vrana, Spence and Lang (1988) to explore the habituation of emotional variables to a realistic depiction of filmed violence. Emotional response was assessed both objectively, using the eyeblink startle response and subjectively through individuals self-reports. In addition the study investigated the significance of individual differences as mediators of emotional response. Questionnaire and physiological data were obtained from 30 participants. Overall, repeated exposure to filmed violence resulted in a decline in both objective and subjective emotional response. Differences were identified in the manner in which men and women responded to the film. Women reacted initially and over time with more intense physiological and psychological reactions to the violent film than males. Specifically, men displayed more curiosity and reported greater entertainment and positive feelings in response to the film, whilst women found the violence more disgusting and reported higher levels of anger and anxiety. It was found that the eyeblink startle magnitude paralleled the subjective emotional processing of the violent film, thus providing further confirmatory evidence of its validity in the investigation of emotional reactions to a stimulus. Personality factors were found to mediate emotional response to filmed violence, with neuroticism most powerfully implicated. High levels of neuroticism were found to be associated with greater anger and anxiety and less positive feelings whilst viewing violent film. A high score on extraversion was correlated with higher levels of anger and lower levels of curiosity and entertainment. Whilst the aims of study 3 were identical to that of study 2, a variation in the contextual feature of the violent film stimuli under investigation was the distinguishing and pertinent feature. Study 2 provided data on the habituation of emotional response to a realistic depiction of filmed violence. Study 3 was concerned with emotional response over repeated exposure to a fantasized violent depiction. Therefore, allowing for a comparison regarding the effects of context on emotional response. The results of study 3, with respect to habituation of emotional response, personality and individual differences, were similar to that obtained in study 2. A comparison of the two studies, however, revealed that individuals responded significantly different to the contextual features of the violent portrayal. Compared to the fantasised portrayal the realistic film stimulus was reported to be more digusting, anxiety provoking and less entertaining. In addition, and not surprisingly respondents reported that the realistic portrayal resulted in the production of more anger and less positive feelings.

The emotion hypothesis of startle eyeblink modification posits that potentiated eyeblinks are observed in response to fear/disgust (aversive) pictures and eyeblink inhibition occurs in response to pleasant (appetitive) pictures due to the degree to which the stimuli match with the aversive startle probe. Stimuli high in arousal elicit exaggerated responses. Four studies sought to investigate the effect of angering pictures on the startle eyeblink response. Three potential hypotheses were posed: 1) given anger's high levels of arousal and negativity, eyeblinks will be potentiated like those to fear/disgust pictures; 2) given anger's arousing and appetitive qualities, eyeblinks will be inhibited like those to pleasant pictures; 3) anger's arousal, negativity, and approach qualities will balance each other out causing eyeblinks resembling those in response to neutral pictures. Study 1 supported the third hypothesis in that eyeblinks to angering and neutral pictures did not differ, despite angering pictures being rated higher on arousal and anger and lower in valence. These results replicated in Study 2 with a different set of angering pictures. Also, Study 2 demonstrated that dysphoric participants exhibited potentiated eyeblinks during angering pictures much like eyeblinks during fear/disgust stimuli, whereas non-dysphoric participants did not. Ratings of pictures on arousal, valence, and anger did not differ between groups. Constructive patriotism related to inhibited eyeblinks during angering pictures. Study 3 found that dysphoric participants rated angering pictures higher in fear than did non-dysophoric participants, suggesting that the potentiated eyeblinks observed in Study 2 were a result of greater perceived fear. Study 4 again showed that eyeblinks during angering and neutral pictures did not differ, and that constructive patriotism related to inhibited eyeblinks. Taken together, results are consistent with the third hypothesis and suggest that angering stimuli elicit eyeblinks much like those to neutral stimuli due to the competing influences of arousal, valence, and motivation on the startle eyeblink reflex.

Lifespan theories of emotion suggest that the ability to regulate emotion improves with age. The supporting evidence, however, is indirect: older adults pay less attention to negative events, remember less negative information, and report fewer experiences of negative emotion. Few studies directly measure emotion regulation by explicitly instructing older adults to modulate their feelings while exposed to emotion-evoking stimuli. The purpose of this thesis was to directly compare younger and older adults in their ability to modulate feelings to investigate whether aging results in decline, stability, or improvement in emotion regulation and also to examine potential mechanisms underlying regulation skills. The study employed a startle modulation paradigm to measure both emotional reactivity and regulation. Two experimental tasks (Stroop colour-word interference, reversal learning) were also administered to explore the relationship between emotion regulation and two theoretically-relevant processes: (a) cognitive control and (b) modification of learned emotional associations. There were three main findings: (1) emotional reactivity was preserved in older adults. Both age groups showed emotion-modulated startle (negative > neutral) during the pre-regulation viewing period; (2) age-related decline in emotion regulation was evident on an objective measure of emotion regulation (startle eyeblink reflex) but not on a subjective measure (self-ratings). Specifically, for older adults, startle eyeblink was not enhanced or attenuated following increase and decrease instructions, respectively. In contrast, both groups showed similar modulation of valence and arousal ratings by regulation instruction (increase > look > decrease); (3) for older adults, reversal learning performance correlated positively with the degree of reappraisal-related startle attenuation in the decrease condition, suggesting a possible mechanism for impaired down-regulation. These findings suggest that even when emotional reactivity is similar, older adults are less effective at modulating their physiological responses.