Schizophrenia is most recognizable by positive symptoms of hallucinations and delusions, but the cognitive deficits and negative symptoms contribute more to functional deficits. The delay discounting (DD) task, with choices between a small immediate reward and a larger delayed reward, tapping into both executive function and reward processing, may prove useful in identifying cognitive and reward processing abnormalities relevant to schizophrenia. In the present study, we used the discounting parameter, k, to assess whether patients with schizophrenia preferred more immediate rewards than healthy controls. We used a model fit statistic, R2, as a measure of choice consistency, quantified using a non-linear regression of participants' responses. Using functional magnetic resonance imaging (fMRI), we investigated group differences between patients with schizophrenia and controls in blood oxygen level-dependent (BOLD) responses to DD decisions in general. In addition, we investigated neural responses to delay discounting decisions varying in difficulty. Compared to controls, patients were more inconsistent in their pattern of responses and exhibited greater DD. However, the difference in DD disappeared when analysis was limited to patients who were consistent in their task performance. Controls, matched on performance and demographics to the consistent patients, displayed greater activation in executive function and reward areas in response to task trials compared to control trials. Compared to controls, consistent patients displayed greater activation to the task relative to the control trials in left insular and temporal cortices and in the precuneus. In response to hard DD trials, controls, when compared to patients, showed more activation in areas associated with executive function, such as the inferior frontal gyrus and the dorsal anterior cingulate cortex. In response to both hard and easy trials, controls showed more activation than consistent patients in the inferior parietal lobule and the ventral striatum. Patients unable to perform the task consistently, when compared to controls, showed greater activation to the DD task in the precuneus and posterior cingulate cortex. In general, patients with schizophrenia appear to have regions of hypoactivation contributing to executive function and reward processing deficits, in addition to hyperactivation in areas associated with resting state and conflict monitoring.
|Advisor:||Lahti, Adrienne C.|
|Commitee:||Cook, Edwin W., III, Cox, James E., Visscher, Kristina M., Weller, Rosalyn E.|
|School:||The University of Alabama at Birmingham|
|School Location:||United States -- Alabama|
|Source:||DAI-B 73/10(E), Dissertation Abstracts International|
|Subjects:||Mental health, Medical imaging, Clinical psychology|
|Keywords:||Delay discounting, Executive function, Fmri, Intertemporal discounting, Reward system, Schizophrenia, Subjective value|
Copyright in each Dissertation and Thesis is retained by the author. All Rights Reserved
The supplemental file or files you are about to download were provided to ProQuest by the author as part of a
dissertation or thesis. The supplemental files are provided "AS IS" without warranty. ProQuest is not responsible for the
content, format or impact on the supplemental file(s) on our system. in some cases, the file type may be unknown or
may be a .exe file. We recommend caution as you open such files.
Copyright of the original materials contained in the supplemental file is retained by the author and your access to the
supplemental files is subject to the ProQuest Terms and Conditions of use.
Depending on the size of the file(s) you are downloading, the system may take some time to download them. Please be