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BACKGROUND: Chronic pain is prevalent among millions of Americans and can negatively impact cognitive processes, mental health, and overall quality of life. Even though pain affects all ethnic and racial groups equally, studies have shown a growing disparity in pain intensity and prevalence of pain conditions among underrepresented minority adult populations across the United States. Hispanics are among the fastest-growing populations in the U.S., yet chronic pain in Hispanic adults and adolescents remains severely understudied. PURPOSE: This study aims to compare pain and related psychosocial factors (pain catastrophizing, anxiety and depression) and Fear of Pain Questionnaire scores (FOPQ) in Hispanic vs. Non-Hispanic White (NHW) youth with chronic pain. Based on prior literature from studies in adults, it was hypothesized that Hispanic youth would report greater pain catastrophizing, anxiety, depression, and higher FOPQ scores when compared to NHW youth. Further, potential differences in relations between anxiety, pain catastrophizing, and physical functioning on depression among Hispanic and NHW youth will be explored. METHODS: Participant data were gathered from the Boston Children’s Hospital Chronic Pain Data Repository. The current study sample included 116 children and adolescents, ages 12-18 years (M = 15.49, SD = 1.71) from Hispanic and NHW backgrounds. Both groups had the same proportion of participants who identified as female (88%), and samples used for analysis were age-and-sex matched. Independent sample t-tests were performed to compare the mean differences in pain catastrophizing, PROMIS anxiety and depression scores, and FOPQ sum score between groups. Bivariate correlations for each group were also compared, and Hayes PROCESS Macro was used to compare the associations between pain catastrophizing, anxiety, and physical functioning on depression, based across patient ethnicities. RESULTS: The results of independent samples t-tests did not reveal any significant differences across groups. However, significant correlations were found. Notably, PROMIS anxiety and depression t-scores were significantly correlated among each independent cohort of Hispanic youth (r = .612, p <.001), non-Hispanic White youth (r = .817, p<.001), and across the full sample (r = .719, p <.001). Pain catastrophizing was also found to be significantly and positively correlated with anxiety (r = .660, p<.001), depression (r = .582, p <.001) and patient FOPQ score (r = .740, p <.001) across both cohorts. From the moderation analysis, the association between pain catastrophizing and depression was found to be statistically significant based on ethnicity of patient [B = .0272, p<.05]. Similarly, ethnicity was found to significantly moderate the association between PROMIS anxiety and depression [B = .0340, p<.05]. CONCLUSIONS: This study is one of the first to explore how pain and psychosocial-related factors compare in an age-and-sex-matched cohort of Hispanic vs. NHW youth with chronic pain. The study is also novel in identifying patient ethnicity as a moderator between anxiety and pain catastrophizing on depression. Obtaining a significant correlation between pain catastrophizing, anxiety, and depression scores for both groups parallels previous findings in adult populations with chronic pain. Contrary to our hypotheses, no mean differences were found in variables associated with pain or psychosocial factors between the two groups, however it is possible that the small sample size used may have obscured group differences. The results highlight the need to increase diversity in research for pediatric populations with chronic pain to help reduce pain disparities among underrepresented minority youth populations.

Social changes associated with aging were assessed in seven captive, socially-housed rhesus monkeys (Macaca mulatta) over a fifteen year period encompassing early, middle, and late adulthood. The changes were evaluated with regard to existing theories about social aging in humans (the theories of social disengagement, activity, continuity, and selectivity). Both quantitative and qualitative measures, as well as analyses of sequential patterns of behavior were used to obtain a complete assessment of changes in social interactions. Analysis of the quantitative measures indicated that highly energetic, non-social behaviors decreased, while affiliative social behaviors either increased or remained stable with advancing age. Tension and agonistic behaviors also decreased. In addition, there were significant changes in the qualitative aspects of social interactions. The time spent in a given affiliative behavior (groom or social contact) increased and negative social interactions decreased across adulthood. The patterns of behavior associated with groom remained highly stable at all points during adulthood, while those associated with passive social contact were more variable. However, these patterns did become less diverse with age. These findings may indicate that groom is used to maintain social ties, while social contact is used for a larger number of social purposes. Although highly energetic activities declined with lower physical stamina in later adulthood, this was not associated with a general decrease in all behaviors. Social interactions were apparently enhanced as evidenced by the increased duration of affiliative behaviors and the decline in negative interactions. These findings do not support the theories of social disengagement or activity, but do provide some evidence to support the selectivity theory. The animals appeared to be maximizing their positive interactions, while minimizing their negative interactions with increased age. In addition, the stability in certain patterns of social behaviors, and the decrease in the diversity of behaviors associated with affiliative interactions further indicates that the establishment and maintenance of social relationships are important during all stages of adulthood, irrespective of advancing age.

Real-time models of classical conditioning were evaluated using simulation and behavioral techniques. Performance criteria included ability to account for aspects of the conditioned response (CR) during conditioning of the rabbit nictitating membrane response (NMR), such as development of CR topography and the dependency of conditioning on the interstimulus interval (ISI) elapsing between onsets of conditioned and unconditioned stimuli (CSs and USs). The models investigated included the Sutton-Barto-Desmond (SBD) model (Moore, Desmond, Berthier, Blazis, Sutton, and Barto, 1986), which predicts CR topography, and the Temporal Differences (TD) model (Sutton and Barto, 1987), which does not. Simulation studies addressed the impact of modifying the TD model to describe topography. The resultant model, called the TD$\sb{RTS}$ model, replicates the learning phenomena described by the TD model but is highly parameter-sensitive. Simulation studies showed the performance of the TD, TD$\sb{RTS}$, and SBD models to be similar in most respects. However, model predictions differ for simultaneous and backwards conditioning protocols involving single and multiple CSs. Behavioral verification of new predictions of the models was carried out using rabbit NMR conditioning. Experiment 1 showed that with fixed-trace-interval conditioning, conditioning increases with CS duration, a result consistent with the SBD but not the TD model. Experiment 1 also showed a novel CS intensity by ISI interaction that none of the models explain. Experiment 2 replicated Experiment 1 and analysed response topography to illustrate problems caused by the CS representation assumed by the models. Experiments 3 and 4 investigated compound conditioning using one CS followed by simultaneous presentation of a second CS and US. Experiments 3 and 4 showed that conditioning to the compound occurred more readily than in controls when the first CS was less salient than the second. Experiment 3 presented weak evidence that the simultaneous CS was inhibitory. Of the models explored, the TD model most fully accounts for the results of Experiments 3 and 4. These computational and behavioral experiments suggested that the models might be better served by alternative CS representations, and highlighted the need for a resolution of issues in simultaneous conditioning. These points and future directions are discussed.

Rats given a footshock 2 min after placement in a box subsequently freeze much more in that box than rats given the shock immediately upon placement. This lack of freezing following the immediate-shock is termed the immediate-shock deficit (ISD), and it is presumed to reflect a learning failure. The purpose of my dissertation was to examine possible mechanisms for the ISD and to further characterize one-trial context fear conditioning. Experiment 1a found the ISD data pattern, but freezing was weak in the delay procedure. Experiment 1b used a smaller box and found enhanced freezing only in the delay procedure. Also, for the delay-shock rats, freezing was distributed on the test day such that freezing increased up to about the time that shock was given on the conditioning day and then decreased. Experiments 2a and 2b used the opioid blocker naloxone to see if the ISD was due to a reduced potency of the immediate-shock brought about by opioid analgesia. The results argued no. Also, for the first time, more freezing and defecation was found in immediate rats than in no-shock control rats. This finding was strengthened by the results of Experiment 3 which measured escape, side preference, side and nose crossings, freezing, and defecation. For each measure, the immediate-shock rats behaved more like the delay-shock rats than no-shock rats. The results of Experiments 2a, 2b, and 3 argue that the ISD is not a complete failure of learning, but instead is only a partial reduction in learning. Experiment 4 found that freezing after experiencing an immediate-shock is not an unconditional effect of shock, but instead reflects learning. Experiment 4 also found that rats shocked 2.5, 15, or 405 s after placement in box freeze less than rats shocked 45 or 135 s after placement. These results suggest that the ISD can be subsumed as a specific instance of a more general interstimulus interval (ISI) effect. Experiments 5a, 5b, and 5c, taken together, determined that an immediate-shock, while only weakly conditioning the context in which it was delivered, could condition other cues that enjoy a more favorable ISI with that shock. This result further suggests that the ISD is not due to any reduced shock potency, but due instead to an unfavorable ISI. The parallel between many of the results found here with those seen in more complex but better studied Pavlovian conditioning models argues that the one-trial context fear conditioning preparation can serve as a simple model system for studying Pavlovian conditioning.

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