To elucidate the neural generator of the feedback error-related negativity (fERN), which is an event-related brain potential (ERP) component elecited following negative feedback, this study utilized a converging method approach by applying electrophysiological methods to replicate a reward task modeled after a functional magnetic resonance imaging, single-cell recording, and primate studies that activated the anterior cingulate cortex (ACC) with negative feedback. This study involved two ERP experiments. The first involved a replication of the reward task and the second experiment involved a modification of the reward task that separated the valence and instructional aspects of the feedback stimulus. Experiment 1 demonstrated that methodological issues can arise when using ERP methods to replicate a paradigm used in other neuroimaging techniques. Experiment 2 was conducted to control for these methodological issues. For experiment 2, the reward condition following a switch movement elicited a large N2 component, which consequently overlapped with the fERN. I concluded that if participants are incorrectly expecting negative feedback after switch trials, the `unexpected' positive feedback following the switch trails violated their expectation, thereby eliciting a large N2, and not a fERN. This hypothesis will be tested in several follow up experiments by modifying the paradigm in Experiment 2 so that all the possible combinations of condition mappings can be applied.

A review of extant literature on positive affect suggested that it has two major dimensions: a hedonic dimension related to subjective feelings and reward processing, and a cognitive dimension related to affect-specific changes in perception and cognition. A novel dopaminergic mod el was proposed to provide a unitary account for the effects of positive affect across the two dimensions. The model hypothesized that positive affect is associated with distinct modes of mesocortical and mesolimbic dopa mine transmission, which in turn mediate unbiased, unfiltered and flexible attention. Three separate behavioral tasks on perception, attention, and reward learning were conducted. In line with the hypothesis, positive affect was found to associate with less biased bi-stable perception, faster regain of attention to previously ignored information, and fewer perseverative errors in face of changing reward contingencies.

A review of extant literature on positive affect suggested that it has two major dimensions: a hedonic dimension related to subjective feelings and reward processing, and a cognitive dimension related to affect-specific changes in perception and cognition. A novel dopaminergic mod el was proposed to provide a unitary account for the effects of positive affect across the two dimensions. The model hypothesized that positive affect is associated with distinct modes of mesocortical and mesolimbic dopa mine transmission, which in turn mediate unbiased, unfiltered and flexible attention. Three separate behavioral tasks on perception, attention, and reward learning were conducted. In line with the hypothesis, positive affect was found to associate with less biased bi-stable perception, faster regain of attention to previously ignored information, and fewer perseverative errors in face of changing reward contingencies.

Behavioral Activation theory (Martell, Addis, & Jacobson, 2001) posits that a pattern of excessive use of avoidant coping strategies removes an individual from environmental sources of reward and reinforcement and subsequently leads to the development (or maintenance) of depressive symptoms. This investigation examined this theory by establishing measures of environmental reward as mediators between avoidance and depression, while further demonstrating that there is a strong connection between avoidance and depression independent of anxiety. Reward was measured by both self-report questionnaire (Reward Probability Inventory; Carvalho et al., under review) and daily activity diary ratings (Hopko, Bell, Armento, Hunt, & Lejuez, 2003), which were considered proxy measures for positive reinforcement. Avoidance was primarily assessed with the Cognitive-Behavioral Avoidance Scale (CBAS; Ottenbreit & Dobson, 2004), which distinguishes between cognitive and behavioral avoidance. When anxiety was controlled, reward significantly mediated the relationships between depression and cognitive, behavioral, and total avoidance. However, when structural equation modeling incorporating latent variables for avoidance and reward tested the same model, reward was not a mediator. In post-hoc mediation analyses, gender differences emerged whereby among females, diary-measured reward only mediated the relation between cognitive avoidance and depression when anxiety was controlled, while in males diary reward was a mediator with all three forms of avoidance. This investigation, while producing mixed results overall, provides initial support for the proposed mediating role of reinforcement in the relationship between avoidance and depression and further highlights the relevance of avoidance and reinforcement in the conceptualization of depression.

Food intake is regulated by both appetite and orosensory reward systems. Appetite systems stimulate or reduce hunger, while orosensory reward motivates consumption of high fat sweet foods, resulting in food enjoyment. The majority of advanced cancer patients suffer from malnutrition and wasting, which may be caused by a loss of appetite due to physiological changes or a hindered orosensory reward system due to taste and smell (chemosensory) changes or both. Orosensory reward systems were hypothesized to be impaired in advanced cancer. To understand the influence of chemosensory alterations on food intake and enjoyment, the nature (intensity) of chemosensory alterations in cancer patients and their relationship with ingestive behaviour and quality of life (QOL) were investigated (study 1). Advanced cancer patients (n=192) more frequently self-reported tastes and odours to be heightened rather than diminished (p=0.035). Patients with perceived chemosensory alterations had poorer QOL (p=0.0176) and lower caloric intake (p=0.0018) compared to patients with no alterations. Cannabinoids (e.g. -9-tetrahydrocannabinol, -9-THC) increase food intake by stimulating both appetite and orosensory reward systems as well as potentially enhancing chemosensory function. To palliate chemosensory alterations and poor appetite, advanced cancer patients (n=21, study 2) with these symptoms were randomized to receive either -9-THC (2.5mg) or placebo oral capsules twice daily for 18 days. Compared to patients receiving placebo, -9-THC-treated patients reported that food tasted better (p=0.04), they had improved chemosensory perception (p=0.026), increased preference and intake of high protein foods (p=0.008), and improved appetite (p=0.05), quality of sleep (p= 0.025), and relaxation (p= 0.045). Like cancer patients, tumour-bearing rats appeared to experience a loss of orosensory reward, showing tumour-associated anorexia when fed a rewarding diet to the same degree as on a usual diet (study 3). -9-THC significantly increased caloric intake compared to vehicle for both tumour-bearing (p=0.0146) and healthy rats (p=0.0004), suggesting endocannabinoid-mediated appetite systems are functioning in this tumour model. The findings of this thesis suggest orosensory reward systems to be impaired in advanced cancer, decreasing the liking and motivation to eat. -9-THC treatment may help to palliate perceived chemosensory alterations and loss of appetite and food enjoyment in advanced cancer. / Food Science and Technology

Typescript. / Thesis (Ph. D.)--University of Hawaii, 1971. / Bibliography: leaves [103]-108. / ix, 108 l graphs, tables

Thesis (M.A.)--University of Toronto, 2005.

Thesis (M. Ed.)--University of Adelaide, Dept. of Education, 1990. / Includes bibliographical references (leaves 99-112).

Diss. (sammanfattning) Göteborg : Göteborgs universitet, 2007. / Härtill 4 uppsatser.

Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.