No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

Dynamics of social processes in populations, such as the spread of emotions, influence, language, mass movements, and warfare (often referred to individually and collectively as contagions), are increasingly studied because of their social, political, and economic impacts. Discrete dynamical systems (discrete in time and discrete in agent states) are often used to quantify contagion propagation in populations that are cast as graphs, where vertices represent agents and edges represent agent interactions. We refer to such formulations as graph dynamical systems. For social applications, threshold models are used extensively for agent state transition rules (i.e., for vertex functions). In its simplest form, each agent can be in one of two states (state 0 (1) means that an agent does not (does) possess a contagion), and an agent contracts a contagion if at least a threshold number of its distance-1 neighbors already possess it. The transition to state 0 is not permitted. In this study, we extend threshold models in three ways. First, we allow transitions to states 0 and 1, and we study the long-term dynamics of these bithreshold systems, wherein there are two distinct thresholds for each vertex; one governing each of the transitions to states 0 and 1. Second, we extend the model from a binary vertex state set to an arbitrary number r of states, and allow transitions between every pair of states. Third, we analyze a recent hierarchical model from the literature where inputs to vertex functions take into account subgraphs induced on the distance-1 neighbors of a vertex. We state, prove, and analyze conditions characterizing long-term dynamics of all of these models. / Master of Science

Current literature suggests neurological (i.e., insula, amygdala) and autonomic (i.e., respiratory sinus arrhythmia; RSA) markers of language, social, and behavioral challenges in autism spectrum disorders (ASD; Bal et al., 2010; DiMartino, Ross, et al., 2009; Lorenzi, Patriquin, & Scarpa, 2011; Patriquin, Scarpa, Friedman, & Porges, 2011), that hypothetically reflect a defensive neurophysiological circuit (i.e., hyper-arousal within the central and autonomic nervous systems). It is unknown how this neurophysiological state contributes to difficulties in ASD. Therefore, the current study quantified peripheral and central nervous system activity and investigated how this neurophysiological circuit may be related to different social and behavioral patterns that characterize ASD. Participants with (n = 16) and without (n = 30) ASD listened to classical music while brain (via functional magnetic resonance imaging) and autonomic (via pulse oximeter and plethysmogram) data were collected. Results indicated that decreased insula and amygdala activity during physiological hyper-aroused states predicted symptoms associated with ASD, and predicted higher levels of comorbid anxiety, stress, and depression. Contrary to hypotheses, no baseline RSA or amygdala differences were noted between ASD and controls groups, suggesting that adults with ASD may have developed effective coping strategies for reducing physiological threat responses. It will be important for future studies to continue to explore and clarify the neural connections of peripheral nervous system activation in individuals with and without ASD, including extending this research to children. / Ph. D.

Due to its relatively cool, humid summers, southwestern Virginia provides an ideal climate for European earwigs, Forficula auricularia. In 1990 - 1992, nymphs were captured in wooden groove-board traps beginning in late May, adults were captured beginning in mid-June, and disappeared from sampling sites by September or October. Sex ratios were significantly female-biased most of the season, becoming more marked by the fall. The pest status of F. auncularia is exacerbated by its gregarious nature. Gas chromatography-mass spectroscopy and accompanying behavioral bioassays showed that aggregation occurred as a result of a pheromone located on the male cuticle, which is probably a minor component of the hydrocarbon profile. Approximately 88% of the detected volatiles on the cuticle were identified as a series of normal and branched alkanes. Fatty acids and hydrocarbons were also identified in nymphal and adult legs, but these extracts were not attractive. Frass, which also contained fatty acids and hydrocarbons, was attractive, but likely acquired its attractancy through the earwigs' proclivity for consuming carcasses and exuviae. The defensive quinones produced by F aunculana repel conspecifics. A study of the behavioral repertoire of F. aunculana showed that, contrary to previous reports, only nymphs are nocturnal. Many differences in behavior were due to gender, age, and partner age. (e.g., females spent more time feeding than did males, adults fed more when paired with nymphs than when paired with adults). Social behaviors (communal feeding, aggression, contact, and dorsal palpation) comprised <10% of the insect's behavioral repertoire. Since dorsal palpation, a previously undescribed behavior and a form of allogrooming, occurred more frequently during reproductive periods, it may have a sexual significance. Dorsal palpation also may augment the distribution of defensive quinones on the cuticle of F. auricularia. An analysis of nymphal group dynamics demonstrated that as group size increased, nymphs spent significantly less time feeding alone and grooming, but more time resting. Antennal contact rates between group members increased significantly with group size. Detailed observations of the courtship and mating of F. auricularia revealed a complex of sexual behaviors for both males and females. Receptive females were behaviorally active during courtship. The significance of the male cerci was demonstrated by their use in early courtship with displays, and later use as a tactile stimulus for the female; and study of males from which the cerci had been removed, which showed no mating by amputated males. Male forcep length was bimodally distributed and positively allometric, while female forcep length was normally distributed. Males with longer forceps did not have a mating advantage. Further research is needed to identify the chemical composition of the aggregation pheromone, and to quantify any advantages of body and forcep size on mating success. / Ph. D.

Juvenile traumatic brain injuries (jTBIs) lead to significant social impairments, with injuries sustained earlier on in development resulting in more significant deficits than when comparable injuries occur later in life. The prefrontal cortex is most susceptible to injury due to its position within the skull and the prevalence of falls as a cause for jTBIs. As neural growth is an ongoing process during the early years, the behavioral deficits observed are shaped by the various stages of development. Injuries during phases with high levels of synaptic pruning or myelination can lead to maladaptive changes resulting in increased synaptic pruning and decreased myelination, causing myriad of deficits that will sometimes appear after the end of these stages. Developing brains also respond differently to injury than adult brains with secondary injury cascades resulting in more cell death than an adult brain, and with unmyelinated fibers demonstrating an increased sensitivity to excitotoxic cell death. Finally, the development of social behaviors are fine-tuned early on and utilize behaviors, such as play, to aid in the appropriate development of adult social behaviors. Disruptions to normal social development are especially apparent when damage involves the prefrontal cortex, resulting in social deficits that impair function in adulthood. While the network for social behavior and cognition involves numerous regions throughout the brain, the medial prefrontal cortex (mPFC), orbitofrontal cortex (OFC) and amygdala are three regions consistently affected by jTBI damage resulting in deficits in social behavior. Disturbance to these regions appear to play principal roles in social behavior as indicated by the observed deficits following a jTBI. These deficits lead to diminished social relationships at the time of injury and continue across development into adulthood. For this study, animals received a single midline cortical contusion injury which resulted in bilateral damage to the mPFC. To evaluate the premise that the development age at injury impacts the resulting social behavioral outcome, the injury occurred on either post-natal day 17 (PND 17) or 28 (PND 28), which in humans approximates toddlerhood and middle childhood, respectively. Following injury, social behavioral development of play behavior and social preference/memory was assessed at each of three time points: prepuberty (post-natal days [PNDs] 35-41), puberty (PNDs 42-48), and young adulthood (PNDs 56-63), while social dominance and aggression were only assessed during young adulthood. Following completion of the study, the animals’ brains were harvested and the dendritic complexity in the orbitofrontal and remaining medial prefrontal regions were assessed using Golgi-Cox staining. The integrity of myelin on axons between the medial prefrontal region, orbitofrontal region, and amygdala were examined using Luxol-Fast Blue staining. Based upon prior research, it was hypothesized that injury at PND 17 would result in a greater degree of social deficits and increased aggression when compared to injury at PND 28 and sham animals. We additionally hypothesized that male jTBI animals would display increased social deficits and aggression relative to their corresponding female jTBI group. It was also predicted that the development of social behavior, including the presence of deficits, would serve as a predictive factor for social dysfunction in young adulthood. Furthermore, as these injuries would be occurring at times when there are ongoing changes in synaptogenesis and myelination, the social deficits observed would be reflected in the histopathology with PND 17 injured animals demonstrating an overall decrease in dendritic complexity and PND 28 injured animals would display less myelin when compared to sham animals. Finally, it was predicted that these histological changes would be more apparent in male subjects when compared to their respective age-at-injury female jTBI groups. The results of our studies supported some of our predictions. With respect to social behaviors, results showed that the initiation of play behaviors were affected but play engagement behaviors were not impacted by jTBI. More specifically, PND 28 injury increased play initiation behavior in both male and female animals in adulthood while a PND 17 injury delayed the normal developmental pattern in females but had no impact on male animals. Surprisingly, injury had no effect on sociability patterns or social memory abilities across development regardless of when the injury occurred. Furthermore, injury at PND 28 increased social dominance behavior in young adulthood, whereas injury on PND 17 did not. This impact of age at injury was also mirrored in the social aggression results with injuries at PND 28 resulting in an increase in aggressive behaviors. Though it is worth noting that sex moderated this relationship for PND 17 TBI animals. Unexpectedly, an injury at this age decreased aggression in male animals and increased aggression in female animals. However, it was specific to the circumstances in the test, as there was no effect on violent social behavior for either the resident or intruder. Lastly, regarding the predictability of play behavior in social outcome, childhood play attacks predicted resident and intruder offensive behaviors and was moderated by sex and injury. For intruder aggression, PND 28 TBI animals displayed higher intruder aggression levels if they displayed several play attacks in childhood at or above the mean level, but not if they display play attacks rates lower than the mean. For resident aggression, a younger injury in female animals but not male animals decreased aggression behavior across development. Finally, our histological results showed no effect of injury or age of injury on dendritic complexity or myelination. However, effect sizes suggested decreased basal and apical complexity and length in both the OFC and mPFC for jTBI animals, as well as decreases in myelin in the mPFC in PND 28 TBI animals. In conclusion, there was a sex- and age at injury-dependent effects of TBI on the development of social behaviors. Injury at an earlier age resulted in more social deficits in female animals while a similar injury at a later juvenile age was more detrimental to male animals. While these observations were not exactly as predicted, these effects are potentially due to sex-dependent developmental trajectories and social interactions, reflecting the need to examine male and female animal subjects both individually and concurrently.