Browsing by Subject "Orbitofrontal cortex"
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Item Subjective response to alcohol in typically developing emerging adults and those with bipolar disorder, associated alcohol use, and orbitofrontal gray matter volume(2019-08-12) Tretyak, Valeria; Fromme, Kim; Lippard, ElizabethCo-occurring alcohol use disorders (AUDs) are highly prevalent in bipolar disorder, though the developmental etiology of this comorbidity remains unknown. A decreased subjective response (SR) to alcohol and differential structure and function of the orbitofrontal cortex (OFC) have been implicated in problematic alcohol consumption in typically developing populations. Differential structure of the OFC has been linked to alcohol use problems in bipolar disorder, yet the underlying mechanisms of this relation are unknown. In this preliminary investigation, SR to alcohol, recent alcohol use, and variation in OFC gray matter volume (GMV)—and associations among these factors—were investigated in 48 emerging adults (24 typically developing, mean age=21, 67% female; 24 bipolar disorder, mean age=21, 75% female). Clinical, behavioral, and structural magnetic resonance imaging data was collected, including Self-Rating of the Effects of Alcohol scale, recent alcohol use, and drinking motives. No significant between-group differences in SR or alcohol use were observed, but a decreased SR to alcohol was associated with greater recent alcohol consumption in both groups (p<.05). Decreased SR to alcohol was associated with lower GMV in OFC in typically developing emerging adults, and greater GMV in OFC in those with bipolar disorder (group by SR interaction p<.001, uncorrected). In both groups, variation in OFC GMV was also differentially related to drinking motives (p<.05). Findings suggest a transdiagnostic association between SR to alcohol and increased alcohol consumption, with differences in OFC structure contributing to this relation. Longitudinal studies are needed to examine how these associations relate to risk/development of AUDsItem Using the neural level of analysis to understand the computational underpinnings of positivity biases in self-evaluation(2012-05) Hughes, Brent Laurence, 1981-; Beer, Jennifer S., 1974-; Gosling, Samuel D.; Neff, Lisa A.; Preston, Alison A.; Swann, Jr., William B.Decades of research have demonstrated that people sometimes provide self-evaluations that emphasize their most flattering qualities. Different theoretical accounts have been offered to explain the mechanisms underlying positively-biased self-evaluation. Some researchers theorize that positively-biased self-evaluations arise from a self-protection motivation because positivity biases increase in situations of heightened self-esteem threat. Alternative views question whether self-protection motivation is a necessary or even dominant source of positivity bias by demonstrating that positively-biased self-evaluations occur even when threat is not heightened, and that a general judgment approach leads to positivity biases in some domains but also to negativity biases in other domains. One reason for this gap in knowledge is that behavioral measures are limited in their ability to resolve whether the processes underlying positively-biased self-evaluation are the same or different depending on contextual motivators. Neuroimaging methods are well suited to examine whether different mechanisms underlie similar behaviors, specifically similar positively-biased responses in different contexts. The four studies presented here explore the neural mechanisms of positively-biased self-evaluation by first identifying a core set of neural regions associated with positivity bias (Study 1A and 1sB), examining whether a heightened self-protection motivation changes the engagement of those neural systems (Study 2), and specifying the precise mechanisms supported by those regions (Study 3). Studies 1A and 1B revealed evidence for a neural system comprised of medial and lateral orbitofrontal cortex (OFC) and, to a lesser extent dorsal anterior cingulate (dACC) that was modulated by positivity bias. Study 2 found that a heightened self-protection motivation changes the engagement of medial OFC in positively-biased self-evaluation. Finally, Study 3 found evidence that medial OFC may support a common mechanism in positively-biased judgment that is implemented differently as a function of the motivational context. Taken together, these studies represent a first step toward developing a neural model of positively-biased self-evaluation. The findings provide some preliminary evidence that positivity biases may represent distinct processes in different motivational contexts. This dissertation sets the stage for future work to examine how specific positively-biased cognitive mechanisms may be supported by specific neural systems and computations as a function of motivational contexts.