The superior cervical ganglion (SCG) is the largest of the sympathetic chain ganglia which control a number of autonomic cardiovascular reflexes via neural activity in the postganglionic nerve trunk. In addition to the large principal neurons, these ganglia contain a minority population of smaller cells, the small intensely fluorescent or SIF cells, so named because of their intense fluorescence following treatments which reveal the presence of endogenous catecholamines (mainly dopamine in the rat). The physiological functions of the SIF cells are largely unknown and various roles have been proposed including (i) dopaminergic interneuron, which modulates ganglionic transmission, (ii) endocrine function, since many of them have a close association with the vasculature and (iii) chemosensory function, similar to that of the arterial chemoreceptors which sense blood gases and pH. Understanding the physiological role of SIF cells has been hampered by their small size, sparse distribution and relative inaccessibility, all of which render microelectrode electrophysiological studies difficult. In this thesis these limitations were overcome by use of (i) dissociated cell cultures of the rat SCG, in which growth conditions favoured SIF cell survival but not that of the principal neurons, and (ii) the novel high resolution patch clamp/whole cell recording technique which is ideal for the study of the electrophysiology of small cells. The ionic currents, which underlie many basic electrophysiological processes, were characterized in 5-16 day old cultures of SIF cells obtained from the SCG of neonatal rats. The main methodology consisted of whole cell recording under voltage clamp conditions, which permit the study of membrane ionic currents. Five main ionic currents were identified in all of the SIF cells ( > 100) studied: (i) a fast transient inward Na+ current, sensitive to the well-known blocker of voltage-gated Na+ channels i.e. tetrodotoxin or TTX; (ii) the delayed rectifier outward K+ current that is found in a variety of cell types; (iii) a Ca2+- activated outward K+ current, sensitive to Ca2+ channel blockers; (iv) a transient inward Ca2+ current which appears to be carried by N-type Ca2+ channels and (v) a slower, sustained inward Ca2+ current which appears to be carried by L-type Ca2+ channels. In addition a third type of outward K+ current, the fast transient K+ current or lA, was found in SIF cells obtained from 3-7 day old rats, but not from 1 day old rats. It therefore appears that this lA current, which is known to modulate firing frequency in neurons develops rapidly in vivo during the first postnatal week. This broad repertoire of ion channels in SIF cells suggests several possible sites for modulation by various agents including neurotransmitters, neuromodulators, or other chemosensitive agents. Since SIF cells were recently proposed to have arterial chemoreceptor function similar to glomus cells, the effect of one such stimulus, i.e. an acidic (intracellular) pH, was tested. It has recently been suggested that a decrease in intracellular pH is part of the pathway responding to extracellular stimuli in the glomus cell (Stea, Alexander and Nurse, in press). Acidification of the SIF cell's cytoplasm with the K+/H+ ionophore nigericin resulted in a suppression of both the fast inward Na+ current as well as the outward K+ current. However, these effects do not appear to beunique to SIF cells and therefore the possibility of a chemoreceptor role m the cardiovascular system requires further study. In summary, the characterization of the various ionic currents in SIF cells resulting from this thesis provides the necessary background which should eventually resolve not only the question of the physiological role of SIF cells in autonomic ganglia, but also help to understand the underlying mechanisms responsible for SIF cell function. / Thesis / Master of Science (MS)

Autism Spectrum Disorders (ASD) are an urgent health concern as new reports indicate approximately 1 in 110 children are affected by ASD (Centers for Disease Control and Prevention, 2009). Although children with ASD struggle with social interactions, quantitative meta-analyses have revealed that traditional social skill interventions only produce minimal effects (Bellini, Peters, Benner, & Hopf, 2007). Due to these minimal effects, this study diverged from the common understanding of social skill deficits and introduced an autonomic nervous system circuit as one root of social behavior problems. Children with ASD show a "fight-flight" (i.e., sympathetic) state at baseline and to unfamiliar individuals (e.g., Bal et al., 2010). Research indicates, however, that music has the ability to calm cardiovascular functioning (Iwanaga, Kobayashi, & Kawasaki, 2005) and improve social behaviors in children with ASD (Whipple, 2004). This study recruited participants (N = 23) between 4-7 years old with a previously diagnosed ASD. Each participant was assigned to a Music group, n = 11, or an Audiobook group, n = 12. The 90-minute experimental session consisted of a receptive vocabulary assessment and psychophysiological monitoring during a baseline video, social engagement task, listening period, and a recovery video. A soothed autonomic state was measured by increased high frequency heart rate variability and decreased heart rate. Results indicated a significant soothing effect for the Music group. Moreover, the Music group evidenced a significant increase in social attention (e.g., joint attention and sharing emotions) relative to the Audiobook group. Mediation analyses may reveal partial mediation for the soothed autonomic state on the relationship between group and social attention improvements. Thus, these results suggest that social skill interventions may not be targeting a core element of social deficits (i.e., over-aroused autonomic state). / Master of Science

The autonomic specificity of emotion is intrinsic for many major theories of emotion. One of the goals of this study was to validate a standardized set of music clips to be used in studies of emotion and affect. This was accomplished using self-reported affective responses to 40 music pieces, noise, and silence clips in a sample of 71 college-aged individuals. Following the music selection phase of the study; the validated music clips as well as film clips previously shown to induce a wide array of emotional responses were presented to 50 college-aged subjects while a montage of autonomic variables were measured. Evidence for autonomic discrimination of emotion was found via pattern classification analysis replicating findings from previous research. It was theorized that groups of individuals could be identified based upon individual response specificity using cluster analytic techniques. Single cluster solutions for all emotion conditions indicated that stimulus response stereotypy of emotions was more powerful than individual patterns. Results from pattern classification analysis and cluster analysis support the concept of autonomic specificity of emotion. / Master of Science / [Appendix B: Beck Depression Inventory, p. 61-64, was removed Oct. 4, 2011 GMc]

The present study investigated the effects of meditative practices on the regulation of autonomic function. 74 subjects (38 women; 36 men) comprised from a range of experienced and non-experienced meditators, engaged in a series of psychophysiological tasks designed to generate specific autonomic states. Regression analyses revealed that experienced meditators, as predicted, displayed greater suppression of myocardial reactivity during a highly reflexive and stressful task. Meditative practice also predicted a rise in electrodermal activity during a relaxation task, contrary to expectations. These results support the concept that meditative practices may alter aspects of autonomic function. Further, these results inform an emerging mind-body paradigm and illustrate the potential consequences of meditative practices in specific disease states and prevention. / Ph. D.

The dynamic behaviors of a complex organism are explained via voluntary and involuntary action. One underpinning of this system is organized and facilitated by the autonomic nervous system, integrating information from conscious and non-conscious centers in a seemingly hierarchical fashion. As a result, voluntary actions have the ability to inhibit reflexive actions via an inhibitory circuit. 111 subjects performed four diverse autonomic tasks consisting of voluntary and involuntary combinations. Analysis supports the proposed hierarchical model. Each task evoked specific autonomic states. Voluntary tasks influenced autonomic actions more than involuntary tasks. And working memory capacity mediated voluntary control. / Master of Science

The present study investigated autonomic nervous system (ANS) patterning during experimentally manipulated emotion. Film clips previously shown to induce amusement, anger, contentment, disgust, fear, and sadness, in addition to a neutral control, were presented to 34 college-aged subjects while electrodermal activity, blood pressure and electrocardiogram (ECG) were recorded as was self-reported affect. Mean and mean successive difference of inter-beat interval were derived from the ECG. Pattern classification analysis revealed emotion-specific patterning for all emotion conditions except disgust. Discriminant function analysis was used to describe the location of discrete emotions within a dimensional affective state space, for both self-report and ANS activity. Findings suggest traditional dimensional emotion models accurately describe the state space for self-reported emotion, but may require modification in order to accurately describe the state space for ANS activity during discrete emotions. Proposed modifications are consistent with the adoption of a discrete-dimensional hybrid model as well as current trends in emotion theory. / Master of Science

Heart rate variability (HRV) has been used to evaluate cardiac autonomic function by measuring variations in electrocardiographic R-R intervals between cardiac cycles. HRV was first used to associate decreases in autonomic nervous system (ANS) control with an increased risk of mortality in coronary heart disease and in the diagnosis of diabetes (1). Current clinical research interest has extended to investigate uses of HRV to evaluate changes in the cardiovascular system due to disease, aging, physical activity, and cardiac rehabilitation treatment (2, 5). HRV scores are derivatives of R-R intervals and these may be represented as a function of either time or frequency domain parameters. Time domain analysis is the simplest and includes: the standard deviation of R-R intervals and the number of adjacent RR intervals that differ by >50ms (dRR50). Frequency domain measures involve more elaborate calculation and have been applied in studies to evaluate sympathetic and parasympathetic autonomic balance. The latter include: Low Frequency Power (LF), High Frequency Power (HF), and LF/HF ratio. HRV has been measured in a variety of ways, the most common being a continuous 24-hour collection of R-R data. In recent years, several investigators have sought to assess HRV by utilizing brief collection periods. Controversy exists about the potential of these short-term sampling intervals to yield reproducible and meaningful measurements of HRV. Many confounders such as respiration, stress, and body positioning can influence HRV, which is why a longer collection period has been accepted as the standard for providing a stable index of ANS function. However, short sampling periods would be useful to evaluate HRV when faced with time constraints. The purpose of the current study was to evaluate the reproducibility of HRV using 8-hour daytime measures with the Polar R-R RecorderTM (Polar Electro Oy, Kempele, Finland) and with short sampling duration of 512 cardiac cycles, using the Schiller AT-10TM device (Schiller AG, Baar, Switzerland). Methods: 10 apparently healthy adult volunteers participated in the study, which was conducted at the Sleep Disorders Clinic in Christiansburg, VA. Each subject performed two HRV trials with the Cardiovit AT-10TM device using recordings of 512 cardiac cycles. Within one or two days following the Schiller, the same subjects wore a Polar R-R RecorderTM device to obtain an 8-hour recording of HRV during waking hours; 24-hour urine samples were collected on the same day. Urine was analyzed for catecholamine levels, including norepinephrine and epinephrine in order to evaluate sympathetic nervous system globally. Each subject recorded their personal impressions of unavoidable physical activity and daytime stress demands on the day of the 8-hour recording and urine collection. This entire protocol was repeated one week later. On one of the days of the short sampling recording, VO2pk also was evaluated for each subject using a ramp protocol on the cycle ergometer and a metabolic cart. Results: The correlation analysis for the HRV response variables using the Schiller method indicated a high-to-very high correlation between trials within a day for the time domain measures (r = 0.75-0.99). The frequency domain measures, however, were low-to-moderately correlated (r = 0.24-0.66) between trials within a day for the Schiller method. Correlations between days for HRV response variables using the Schiller method were similarly low for both time (r < 0.5) and (r < 0.4) frequency domain measures. Correlation coefficients between days for the HRV response variables using the Polar method were moderate (r = 0.59-0.67) for the time domain and only low-moderate for the frequency domain measures (r = 0.37-0.69). However, an important finding was that Polar R-R data for two of the subjects contained excessive signal artifact, which affected the fidelity of the HRV scores. When these two cases were excluded from the group analyses, the resulting correlations were high-very high for all time and frequency domain measures (r = 0.70-0.93). The means for each response HRV time and frequency domain variable between the Polar method and Schiller method were significantly different (P < 0.05). Additional correlational analyses did not reveal any systematic associations between HRV measures and simple markers of sympathetic activity (urinary NE or E) and aerobic fitness (VO2pk) in this small sample of subjects. Conclusions: Due to this important change in reproducibility with the Polar method, the consequence of artifact-free recordings is unmistakable. Within the limitations of this small study sample it is concluded that, while HRV in apparently healthy adults may not be measured reliably with brief data collection periods, longer daytime sampling periods of 8 hours (e.g. Polar device) yields acceptable reliability for both time and frequency domain parameters of HRV. / Master of Science

There is clear evidence that the autonomic nervous system (ANS) is lateralized at both the peripheral as well as the central levels of the nervous system. Both the vagus and the sympathetic ganglia asymmetrically innervate the sino-atrial node and the myocardium of the heart. This lateralization has also been observed in afferent as well as efferent projections to nuclei in the brainstem, hypothalamus, and amygdala. Where laterality has not been as clear is in regions of the frontal lobe dedicated to the regulation of autonomic nervous system responses. This study addressed that issue via the implementation of lateralized autonomic response-evoking tasks. With the use of cardiovascular and electrodermal measures, the present study indexed autonomic responses to lateralized stimuli. This study also explored the role of lateralization within sex as well as in relation to reported gender identity. The findings lend support to the right hemisphere as serving a dominant role in regulating sympathetic nervous system activity, while lending less conclusive support for lateralization of parasympathetic nervous system regulation. Men demonstrated greater lateralization for sympathetic nervous system responses across several different metrics of autonomic indices. The exploration of gender variables in relation to lateralization of autonomic responses was generally not supported. / Master of Science

Anxiety and its cognitive component of worry have been related to exaggerated cardiovascular reactivity and delayed recovery to laboratory stressors, and to increased risk of cardiovascular disease. Previous research on the anxiety-cardiovascular system relationship, including data from Knepp and Friedman (2008), are included to support this project. Two experiments were completed during the course of this study. The first consisted of two peripheral-based body positioning tasks. The second experiment used an active versus passive sympathetic stress task paradigm (mental arithmetic, hand cold pressor). Subjects were nonsmokers free of cardiovascular and neurological disease. Trait worry was examined through the Penn State Worry Questionnaire (PSWQ). Blood pressure recordings and cardiac recordings through ECG and ICG were done in each experiment during seven epochs: an anticipatory baseline with three baselines preceding and three recovery periods following each task. Repeated measures analysis was run on all cardiovascular measures. In the first experiment, high worriers had worsened blood pressure reactivity to task. The second experiment found that high worriers had increased stroke volume across all epochs. There were mixed findings in the studies relating to subjects acclimated to the laboratory experience. Future directions of research relating anxiety, worry, and cardiovascular risk factors are discussed. / Ph. D.

Ego-resiliency (ER) is a trait that describes the ability to cope with stress, while effortful control (EC) is an individual difference related to the ability to optimally inhibit negative emotion through attentional mechanisms. ER has been linked to flexible cardiovascular responding without accounting for autonomic nervous system origins of physiological responses. Similarly, EC tends to be associated with increased cardiac vagal control. However, differences in the autonomic characteristics of these constructs remain unclear. In the current study, it was hypothesized that compared to low-scorers, individuals who score high on ER and EC will each have greater vagal control and less sympathetic control over interbeat intervals (IBI) changes during laboratory stressors. Subjects engaged in a mental arithmetic, speech preparation, and verbal fluency task to elicit cardiovascular activation along a continuum of threat. Electrocardiography and impedance cardiography were collected before, during, and after these tasks to assess changes in autonomic functioning. Results from multiple regression analyses indicated that high levels of EC predicted increased vagal control over IBI recovery and less sympathetic reactivity of IBI reactivity. Contrary to predictions, ER showed an opposite pattern of autonomic regulation across stressors. / Master of Science