Thesis (Ph.D.)--University of Texas at Dallas, 2008. / Includes vita. Includes bibliographical references (leaves 187-189)

published_or_final_version / Psychology / Master / Master of Philosophy

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Selective attention involves focusing on one event among many, and is largely responsible for an organism's ability to respond efficiently to the environment. The location at which attention is focused is a function of an ongoing tension between external cues and internal goals. Control over selective attention is often described as an executive process, attributable to the function of the frontal lobes of the brain. The present experiments investigated the role of the frontal cortex in attentional control, through the study of patients with focal cortical lesions and through functional neuroimaging in neurologically normal subjects. It was found that patients with unilateral surgical resections from the frontal cortex were as efficient as patients with temporal-lobe resections and normal controls at attending selectively to a visual stimulus at one location in the presence of irrelevant distracting stimuli. In fact, those patients whose lesions invaded the anterior cingulate gyrus tended to be less reactive to changes in irrelevant stimuli. However, patients with frontal cortex lesions were mildly impaired in a different task in which they used visual cues to direct attention voluntarily to a different location from one trial to the next. In addition, patients with excisions from the right frontal cortex performed less efficiently with increasing time spent on a task, suggesting an important role for this region in sustained attention. These observations prompted a further study of attention using positron emission tomography in normal subjects. This experiment was designed to identify the brain regions that were more active during trials in which cues could be used to direct attention voluntarily, relative to trials in which uninformative cues were presented. The striatum and extrastriate cortex were the only regions in which blood flow correlated positively with the proportion of trials containing informative cues. The present studies indicate that the frontal

Thesis (PhD) - Swinburne University of Technology, School of Biophysical Sciences and Electrical Engineering, 2004. / A thesis submitted for the degree of Doctor of Philosophy, School of Biophysical Sciences and Electrical Engineering, Swinburne University of Technology - 2004. Typescript. Includes bibliographical references (p. 259-287).

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The principal aim of this thesis was to test the conjecture of Schacter et al. (1995) that the false memory effect in the Deese-Roediger-McDermott (DRM) paradigm is generated by errors in source monitoring and is mediated by frontal lobe circuits. In support of their conjecture, Schacter et al. cited evidence from elderly populations with presumed frontal dysfunction, however this thesis studied children over an age range over which the frontal lobes are believed to be maturing. This thesis represents the first attempt to specifically test Schacter�s hypothesis based on the developmental trajectory of �frontal� functioning. Moreover, the use of a developmental trajectory in such a manner is relatively novel, and a key issue within this thesis is how to operationalise �frontal� functioning in the sense intended by Schacter et al. Extrapolating from Schacter�s conjecture, it was predicted that the strength of the false memory effect is directly proportional to the degree of frontal maturation, as estimated by both chronological age and by performance on a range of neuropsychological tests of �frontal� executive functioning. False memory and executive functioning were compared in children aged 8 to 12 years and in adults using a modified DRM paradigm with a source monitoring extension after Payne et al. (1996). The modified DRM elicited false memory effects comparable to those reported in adolescents by Newstead and Newstead (1998) and in adults by Roediger and McDermott (1995) and by Payne et al. (1996). Three experiments that demonstrate a strong developmental trajectory for false memory effect are reported, but the pattern of results is not consistent with all of the premises of the conjecture. Although false recognition rates increased significantly with age, source monitoring accuracy did not change across the age groups. Consistent with the principal assertion of the conjecture by Schacter et al., age and a general �frontal� factor were found to be significantly related to the size of the false memory effect. In addition, veridical memory performance was always a predictor of false memory performance. The IAR (Underwood, 1965) theory can best account for the significant covariation between veridical and false memory development, as well as being able to account for the dissociation between false memory and source monitoring.

Whereas some researchers claim that the holistic processing of the right hemisphere is essential for contextual integration in language pragmatics (Myers, 2001, Myers, 2005), results of other studies point to involvement of executive processes of the frontal lobes (McDonald & Pearce, 1998; Bernicot & Dardier, 2001). This study examined the role of frontal lobes in language pragmatics by testing performance of young adults and older adults on selected standardized pragmatic inferences called 'implicitures'. Implicitures were first presented free-standing and then embedded in contexts that either supported (enabling contexts) or cancelled (cancelling contexts) their preferred meaning. First, implicitures were examined using behavioral reaction time measures in young adults. The second part of the project addressed the question about involvement of frontal lobes in language pragmatics by testing older adults with varying degrees of frontal function on processing of implicitures. Finally, event-related potential responses to implicitures with and without context in young adults were explored. Results revealed a strong relationship between frontal lobes and performance on implicitures in canceling contexts in older adults. There was no significant effect for free-standing implicitures and implicitures presented in enabling contexts. In addition, an N400 was observed to free-standing implicitures, but implicitures in context elicited a negative component in the later 400 ms window at the anterior sites. These results indicate that frontal lobes are important for pragmatic processing requiring integration of linguistic context with an utterance for the correct interpretation. Consequences of our findings for models of impliciture processing and accounts of neural architecture underlying language pragmatics are considered.