Author's School

Graduate School of Arts & Sciences

Author's Department/Program

Psychology

Language

English (en)

Date of Award

January 2009

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Chair and Committee

Deanna Barch

Abstract

Individuals with schizophrenia demonstrate cognitive deficits in a number of domains, including episodic memory: EM). Memory for both individual items and associations between items is impaired in schizophrenia, with some indication of a more severe deficit in associative memory. Furthermore, such memory impairments have been consistently linked with abnormalities in brain activation during both encoding and retrieval. However, certain experimental manipulations at the encoding and retrieval stages of EM significantly benefit memory performance in schizophrenia, suggesting that a strategic processing deficit may underlie memory impairment in schizophrenia. Additionally, the provision of beneficial encoding strategies increases encoding-related brain activity in key memory processing regions in schizophrenia participants, although such manipulations have not yet been tested in participants with schizophrenia during retrieval. The goal of the current study was to examine the impact of encoding and retrieval strategies on associative memory function and brain activity in schizophrenia. Behavioral and functional neuroimaging data were collected from 23 DSM-IV diagnosed participants with schizophrenia and 24 demographically equivalent comparison subjects while performing associative memory encoding and recall tasks in the fMRI scanner. Two factors of interest were manipulated and studied: 1) orientation to the semantic relatedness of associative pairs; and 2) provision of memory cues at subsequent recall. Behaviorally, schizophrenia participants: like controls) demonstrated significant memory benefits from both the provision of support for effective encoding: orientation to semantic relatedness) and retrieval strategies: provision of memory cues). In addition, support for the use of an effective encoding strategy was also associated with increased brain activity in a variety of brain areas in schizophrenia participants, whereas the manipulation of retrieval strategies did not serve to increase retrieval-related brain activity among individuals with schizophrenia. Lastly, both groups showed significant associations between inherent semantic processing ability and episodic memory performance. Schizophrenia participants also demonstrated significant associations between semantic processing ability and semantic encoding-related brain activity in prefrontal cortex, whereas controls did not show any such relationships. Overall, these findings suggest that memory performance in schizophrenia can be improved via manipulations at the encoding and retrieval stages, and that brain activity enhancements are observed under supportive encoding conditions as well. These data also provide evidence that individual differences in cognitive abilities among individuals with schizophrenia can significantly affect behavioral and neurobiological responses to strategic memory interventions. Finally, the current findings suggest that individuals with schizophrenia and healthy individuals rely on partially overlapping networks of brain regions to support EM processes under supportive conditions. Although certain deficits in memory performance and brain activation persist, it is clear that orientation to advantageous memory strategies can partially ameliorate EM function among individuals with schizophrenia.

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Permanent URL: http://dx.doi.org/10.7936/K7707ZJT

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