Synaptic alterations in the nucleus accumbens (NAc) are crucial for the aberrant reward-associated learning that forms the foundation of drug dependence. Glutamatergic synaptic plasticity in the NAc has been implicated in several behavioral responses to psychomotor stimulating agents, such as cocaine and amphetamine, yet no studies, at present, have investigated its modulation by ethanol. We demonstrated that both in vitro and in vivo ethanol treatment significantly disrupts normal synaptic functioning in medium spiny neurons (MSNs) of the NAc shell. Utilizing whole-cell voltage clamp recording techniques, synaptic conditioning (low frequency stimulation with concurrent postsynaptic depolarization) reliably depressed (NAc-LTD) AMPA-mediated excitatory postsynaptic currents (EPSCs). Acute ethanol exposure inhibited the depression of AMPA EPSCs differentially with increasing concentrations, but this inhibitory action of ethanol was reversed by a D1-like dopamine receptor agonist. When examined 24 hours following a single bout of in vivo chronic intermittent ethanol (CIE) vapor exposure, NAc-LTD was absent and instead synaptic potentiation (LTP) was reliably observed. We further investigated CIE-induced modulation of NAc-LTD by distinguishing between the two subpopulations of MSNs in the NAc, D1 receptor-expressing (D1+) and D2 receptor-expressing (D1-). We determined that NAc-LTD is expressed solely in D1+ but not D1- MSNs. In addition, 24 hours following a repeated regimen of in vivo CIE exposure NAc-LTD is completely occluded in D1+ MSNs, while D1- MSNs are able to express LTD. Complete recovery of normal synaptic plasticity expression in both D1+ and D1- MSNs does not occur until two weeks of withdrawal from CIE vapor exposure. To our knowledge, this is the first demonstration of a reversal in the cell type-specificity of synaptic plasticity in the NAc shell, as well as, the gradual recovery of the pre-drug exposure plasticity state following extended withdrawal. This study suggests that NAc-LTD is cell type-specific and highly sensitive to both acute and chronic ethanol exposure. We believe these observations also highlight the adaptability of NAc MSNs to the effects of long-term ethanol exposure. A change in these synaptic processes may constitute a neural adaptation that contributes to the induction and/or expression of alcohol dependence. / text

Considerable research has been done on measuring dependence between random variables. The correlation coefficient is the most widely studied linear measure of dependence. However, the limitation of linearity limits its application. The informational coefficient of correlation is defined in terms of mutual information. It also has some deficiencies, such as it is only normalized to continuous random variables. Based on the concept of the informational coefficient of correlation, a new dependence measure, which we call the L-measure, is proposed in this work which generalizes Linfoot's measure for both continuous and discrete random variables. To further elucidate its properties, simulated models are used, and estimation algorithms are also discussed. Furthermore, another measure based on the L-measure, which we call the intrinsic L-measure, is studied for the purpose of studying nonlinear dependence. Based on criteria for a dependence measure presented by Renyi and simulation results in this thesis, we believe that the L-measure is satisfactory as a dependence measure. / Thesis (Master, Mathematics & Statistics) -- Queen's University, 2011-09-30 14:29:35.153

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No description available.

The first aim of this study was to explore the prevalence of Exercise Dependence (ED) in the Norwegian male population. The second aim was to examine what characterize men with high scores on Exercise Dependence Scale–Revised (EDS-R), when it comes to mode of exercise, exercise frequency, exercise intensity, exercise at a competitive level and hours exercising at the gym. To achieve these aims 5000 questionnaires were sent to randomly selected men between 18 and 65 years in Norway, and 1824 returned completed forms. Cases were excluded when data were missing and the final sample consisted of 1546 men. The questionnaire consisted of the Norwegian translated version of the Exercise Dependence Scale- Revised (EDS-R), demographic items and items that inquired about exercise-related characteristics. Results showed prevalence of exercise dependence in the male Norwegian population of 0.4%, and a higher occurrence of exercise dependence symptoms (21.4%). Higher total EDS-R score were found among these sub-groups of men: men engaging in power and weight class sports, exercising frequently, that often exercise with high intensity, exercising at a competitive level, and exercising more than 5 hours a week at the gym. The results offer insight into ED in the Norwegian male population, but more research is needed to further elucidate the phenomenon.

Thesis (Ph. D.)--Westfälische Wilhelms-Universität, 1975. / Vita. Bibliography: p. 241-259.

Thesis (D.A.)--Illinois State University, 1987. / Title from title page screen, viewed August 23, 2005. Dissertation Committee: Janice G. Neuleib (chair), Ronald J. Fortune, Gail E. Hawisher, Elizabeth S. McMahan, Janet M. Youga. Includes bibliographical references (leaves 132-143) and abstract. Also available in print.

Thesis (Ph. D.)--Westfälische Wilhelms-Universität, 1975. / Vita. Bibliography: p. 241-259.

Background: Changes in neuropsychological and emotional systems are associated with substance dependence and reduce the chance of successfully maintaining abstinence after treatment. Impulsivity is strongly associated with substance dependence and is a risk factor for development, a consequence of excessive use and a marker for poor treatment outcomes. The focus of this thesis is impulsivity, as well as emotional and motivational factors, in the context of harmful substance use and dependence. The thesis is formed of two parts; the first (Studies 1 and 2) focusses on the multi-faceted role of impulsivity in substance dependence. The second part (Studies 3 and 4) investigates negative reinforcement and automatic approach and avoidance behaviour in heavy alcohol use. Study 1: A multi-dimensional investigation of impulsivity in abstinent substance dependent individuals using three complementary techniques: self-report, behavioural and neural measures. Results suggest that self-report measures of impulsivity are more sensitive in abstinent individuals than behavioural or fMRI measures. Study 2: An alternative approach to the classification of substance dependent individuals; using Latent Profile Analysis, abstinent substance dependent participants from Study 1 were regrouped based on personality risk factors rather than primary dependence. Important differences were detected within a previously undifferentiated group of abstinent substance dependent individuals; notably the greater incidence of childhood adversity and stimulant dependence history in one group, while the other did not differ from controls. Study 3: A behavioural investigation of the effect of stress induction on automatic approach and avoidance in heavy drinking individuals compared to light drinkers. Results indicated no differential effect of stress. These findings may suggest that the behaviour of older, more established heavy drinkers is comparable to that of alcohol dependent participants and reflects an advanced stage along the spectrum of alcohol use and dependence. Study 4: An fMRI investigation conducted on a subset of participants from Study 3 using neuroimaging paradigms to assess automatic approach and avoidance behaviour in heavy drinking individuals compared to light drinkers. Results can be interpreted to suggest that heavy drinkers approach alcohol in a less controlled manner than light drinkers, and that trait anxiety may be involved in the extent of avoidance behaviour. Conclusions: Although there are more questions raised by this research than are answered, some general conclusions can be drawn. Specifically, impulsivity measures need to be made more appropriate to all stages of substance use and dependence. Furthermore I propose a longitudinal theory of substance use and dependence with different neurocognitive profiles at each stage, as well as individual differences throughout the trajectory. This has implications for future addiction research that should enable better understanding for the benefit of clinical practice and treatment of substance related disorders.