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

This study examined the effects of genetic background on the acoustic startle response (ASR) and its modulation by prepulse inhibition (PPI) by comparing nine inbred strains of mice. The ASR, a jerk-like motor reflex, is elicited by bursts of noise or tones with sound pressure levels of 80-90 dB and greater. PPI is a type of modulation of the ASR, requires no training, and results in observable response in both mice and humans. Data were obtained from nine inbred mouse strains, sixteen per strain, which were shipped at approximately 3-5 weeks old from The Jackson Laboratory. In general, ASRs were generally smaller when the startle stimulus was less intense. PPI was relatively weak for the 4 kHz prepulse, and stronger with prepulses of 12 kHz and 20 kHz. However, means varied widely across strains for both ASR and PPI, suggesting a strong influence of genetic background on these behaviors. In addition to genetic influences, peripheral hearing loss and central auditory processing factors must be taken into consideration.

Infrared thermal imaging of the periorbital regions of the face shows promise as an input signal modality for an alternative communication system for individuals with conditions that preclude speech or voluntary movement, such as total locked-in syndrome. However, it was unknown if the startle response triggers a change in the skin temperature of these regions; such a change could generate false positives in a thermography-based access system. This study presents an examination of the temperature characteristics of the periorbital regions of 11 able-bodied adult participants before and after an auditory startle stimulus. The results show that the startle response has no substantial effect on the mean temperature of the periorbital regions. This indicates that thermography-based access solutions would be insensitive to startle reactions in their user, an important advantage over other modalities being considered in the context of access solutions for individuals with a severe motor disability.

Infrared thermal imaging of the periorbital regions of the face shows promise as an input signal modality for an alternative communication system for individuals with conditions that preclude speech or voluntary movement, such as total locked-in syndrome. However, it was unknown if the startle response triggers a change in the skin temperature of these regions; such a change could generate false positives in a thermography-based access system. This study presents an examination of the temperature characteristics of the periorbital regions of 11 able-bodied adult participants before and after an auditory startle stimulus. The results show that the startle response has no substantial effect on the mean temperature of the periorbital regions. This indicates that thermography-based access solutions would be insensitive to startle reactions in their user, an important advantage over other modalities being considered in the context of access solutions for individuals with a severe motor disability.

This study investigated the electromyogram eyeblink startle response in relationship to individual differences in dimensions of attention and arousability as assessed by the Cognitive Failures Questionnaire (Broadbent, Cooper, Fitzgerald & Parkes, 1982) and the Arousal Predisposition Scale (Coren, 1990). Individuals (n=48) fulfilling the cutoff criteria of the questionnaires compiled three groups: High Arousal/High Cognitive Failures, High Arousal/Low Cognitive Failures and Low Arousal/Low Cognitive Failures. The eyeblink startle response was examined in two conditions, one in which participants were instructed to attend to loud, startling acoustic stimuli and a second in which they were instructed to ignore the startling stimuli by mentally counting backwards by threes. It was hypothesized that groups would differ from each other in both amplitude and latency of their startle response. More specifically, if top-down controlled attentional processes mediated the startle response under such conditions, it was expected that those with less distractibility would exhibit less startle during the ignore task than those who were more distractible. If arousal level mediated the startle response, it was expected that those with high arousability would exhibit increased overall startle response. If the ignore condition was more arousing, it was expected that those with high arousability would exhibit more startle during the ignore condition than those with low arousability. It was expected that the startle response between men and women would differ significantly. Furthermore, it was hypothesized that those participants reporting high distractibility would demonstrate a larger Stroop Effect than those reporting low distractibility. Results indicated that for mean startle response amplitude there was a significant Attention Group X Condition interaction but not an Arousal Group X Condition interaction. Post hoc tests did not reveal one condition to be greater in mean amplitude than another. When including sex as a factor, for mean onset latency there was a significant Attention X Gender interaction and a significant Arousal X Gender interaction. High arousal and high distractible men also showed significantly more significantly more startling than low distractible men and low distractible women. There were no significant differences of the Stroop Effect found between high and low distractible participants. Taken together, it appears that controlled top-down processing can influence the startle response when manipulations of the direction of attention are given. It also appears that men are more extreme in their responsivity than women. Implications for future research are discussed. / Master of Science

Millions of people suffer from tinnitus, a disorder for which there is currently no effective treatment or cure. My dissertation work provides insight into the neural correlates of this pervasive hearing disorder and examines how a newly emerging therapy, transcranial magnetic stimulation (TMS), affects the central auditory system in the generation of the tinnitus percept. This work has a multifold focus of: i) developing and modeling the function of a miniature magnetic coil that can be used for TMS in rodents, ii) establishing a reliable mouse model of tinnitus that can be used for assessing TMS treatment-induced changes, iii) measuring the behavioral alterations and neural changes induced by TMS throughout the auditory system in mice with tinnitus, and iv) to assay underling molecular changes in the auditory cortex (AC) related to TMS and tinnitus. Chapter 1 gives an overview of the current research on tinnitus and TMS. Chapter 2 establishes a reliable neural and behavioral assay of verifying tinnitus in a mouse model and provides further evidence that the underlying hyperactivity associated with tinnitus is initiated in the brainstem following reduced afferent input. The remainder of the dissertation examines the modulation of tinnitus in the auditory central nervous system using a miniature TMS coil. Chapter 3 of the dissertation details the creation and evaluation of a rodent-sized TMS coil, which could increase the overall effectiveness and applicability for human treatment. TMS is currently an FDA approved treatment of depression and has been shown to decrease tinnitus perception in human clinical trials, albeit with variable results. There have been few published studies of tinnitus modulation by TMS using animal models and therefore little is known about the molecular and neural bases of this potential tinnitus treatment. TMS is thought to be therapeutic because the magnetic flux generated from the electromagnetic coil induces an electric field in the brain, altering ion flow and subsequently neural function, as the excitation and inhibition of cortical networks become synchronized to the magnetic pulse. Chapter 4 demonstrates that TMS with our custom-designed miniature rodent coil can successfully reduce behavioral evidence of tinnitus in a mouse model, mainly through activating inhibitory networks in the AC. It also shows that presynaptic activity is altered in the upper layers of the AC responsible for intralaminar processing and sound perception. Finally, chapter 5 describes an in-depth proteomic analysis of over 3000 proteins from the AC, which shows that TMS and noise-induced tinnitus alter the expression of several key proteins and pathways that play a critical role in cortical excitatory and inhibitory activation. The results of this work are also important because they are the first animal model to demonstrate neural changes during TMS-treated tinnitus, creating a paradigm that can be used for optimizing parameters to improve clinical outcomes in human trials.

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.

Toxoplasma gondii infection is common in humans and is a significant risk factor for developing the disease schizophrenia. Genetic risk factors are likely required for the disease of schizophrenia to develop. Nurr1 – heterozygous (+/-) mice and wild-type (+/+) mice were evaluated using immune activation of astrocytes within the prefrontal cortex, dopamine levels within the striatum, and measuring the acoustic startle response reaction time by using prepulse inhibition (PPI). T. gondii infected heterozygous (+/-) mice exhibited increased GFAP expression within the prefrontal cortex. Dopamine levels within the striatum were measured and T. gondii infected wild-type (+/+) mice exhibited increased dopamine levels. The acoustic startle response reaction time was measured using PPI and T. gondii infected mice exhibited slower reaction times when compared to controls. These data demonstrate that the Nurr1 (+/-) genotype predisposes mice to T. gondii-induced alterations in behaviors that involve dopamine neurotransmission and are associated with symptoms of schizophrenia.

Women are twice as likely as men to suffer from depression and anxiety disorders and have an increased risk of onset during periods associated with hormonal changes, such as the postpartum period and the menopausal transition. Furthermore, some women seem more sensitive to normal hormone fluctuations across the menstrual cycle, since approximately 3-5% suffers from premenstrual dysphoric disorder (PMDD). Why these disorders are so common in women has not been established but there is a probable involvement of the ovarian hormones. The aim of this thesis was to investigate the effect of the ovarian hormones on the female brain during different reproductive states using psychological tests known to affect brain activity in different ways. Paper one examined the effect of the ovarian hormones on prepulse inhibition (PPI) on the acoustic startle response (ASR) and comprised cycling women and postmenopausal women. The cycling women had lower levels of PPI compared to postmenopausal women and postmenopausal women with moderate estradiol levels had lower PPI compared to postmenopausal women with low estradiol levels. Paper two examined the effect of anticipation and affective modulation on the ASR in women with PMDD and healthy controls. Women with PMDD have an increased modulation during anticipation of affective pictures compared to healthy controls during the luteal phase of the menstrual cycle. Paper three examined brain activity during response inhibition among women with PMDD and healthy controls by the use of a Go/NoGo task and fMRI. Women with PMDD displayed a decreased activity in the left insula during follicular phase and an increased activity during the luteal phase compared to controls. Paper four comprised women in the postpartum period and non-pregnant controls to examine brain activity during response inhibition. While this study revealed decreased activity at 4 weeks postpartum compared to 48 hours postpartum we cannot ascertain the role of the ovarian steroids, since none of the significant brain areas correlated with ovarian steroid or neurosteroid serum concentrations. The results of this thesis demonstrate that the ovarian hormones, or at least various hormonal states, have a probable impact on how the female brain works.

Title from PDF of title page. / Document formatted into pages; contains 18 pages. / Thesis (Au.D.)--University of South Florida, 2003. / Includes bibliographical references. / Text (Electronic thesis) in PDF format. / ABSTRACT: This study examined the effects of genetic background on the acoustic startle response (ASR) and its modulation by prepulse inhibition (PPI) by comparing nine inbred strains of mice. The ASR, a jerk-like motor reflex, is elicited by bursts of noise or tones with sound pressure levels of 80-90 dB and greater. PPI is a type of modulation of the ASR, requires no training, and results in observable response in both mice and humans. Data were obtained from nine inbred mouse strains, sixteen per strain, which were shipped at approximately 3-5 weeks old from The Jackson Laboratory. In general, ASRs were generally smaller when the startle stimulus was less intense. PPI was relatively weak for the 4 kHz prepulse, and stronger with prepulses of 12 kHz and 20 kHz. However, means varied widely across strains for both ASR and PPI, suggesting a strong influence of genetic background on these behaviors. / ABSTRACT: In addition to genetic influences, peripheral hearing loss and central auditory processing factors must be taken into consideration. / System requirements: World Wide Web browser and PDF reader. / Mode of access: World Wide Web.