Investigations in Discourse Processes

This protocol is designed to acquire a better understanding of the underlying cognitive mechanisms involved, and the roles of the prefrontal cortex and normal aging, on various aspects of discourse processing. For Phase 1 of the investigations, two investigations will be conducted: Study 1 will compare the performance of patients with prefrontal cortical damage with age-matched healthy controls; Study 2 will compare the performance of young healthy subjects with older healthy subjects in various aspects of on-line discourse processing. The primary focus of our investigations will be on the cognitive mechanism of suppression, which allows selection of appropriate meanings when information is ambiguous. A secondary focus will be on the cognitive processes involved in comprehending explicit and implicit information in stories and appreciating their thematic aspects. In addition, we are interested in learning how individuals comprehend visual (pictorial) versus propositional (textual) representations of relational language concepts (e.g., more/less, front/back). From a cognitive neuroscience perspective, our interests are in investigating the roles of both the prefrontal cortex (i.e., prefrontal lateral and orbitomedial areas of either hemisphere) and the normal aging process in these aspects of discourse processing. We predict that: (1) patients with frontal lobe lesions will have difficulty in suppressing mental activation of inappropriate meanings of ambiguous text at various points during ongoing processing; (2) aging reduces the efficiency of suppressing contextually inappropriate meanings of ambiguous text; (3) prefrontal cortex damage will have deleterious effects on processing implied information in stories and appreciating their thematic aspects, and (4) prefrontal cortex damage will impair visual rather than propositional representations of relational language concepts. Phase 2 of the investigations is designed to extend study into other aspects of text processing as well as expands to the study and analysis of discourse production. Our specific intents are to (1) investigate the processing and use of context when encountering garden path phenomena in text; (2) understand the nature of breakdowns in discourse production during story tell/retell using sequential pictorial stimuli that probe for temporal sequencing of events, cohesive ties, cause/effect relationships, anaphoric reference, inference, and gist; (3) understand what role the prefrontal cortex plays in its ability to formulate a coherent representation in narrative text inferencing tasks. Our findings will be of value in contributing to knowledge about the neural representation of the cognitive mechanisms underlying various aspects of discourse processes; advancing clinical measurements that can pinpoint breakdowns in these processes as they occur in real time, and understanding the effects of normal aging on discourse processes.