Melbourne School of Psychological Sciences - Theses
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ItemEarly neuropsychological change in possible dementia of the Alzheimer type( 1996)Early detection of dementia of the Alzheimer type (DAT) is vital in understanding the natural course of the disease, which in turn guides the development of potential pharmacological treatment and management strategies. However, early detection of DAT has traditionally proved difficult. The study described in this thesis comprehensively examined neuropsychological function over a 24 month period in patients with early dementia, using as comparison groups individuals with isolated memory complaints (questionable dementia, QD), and normal controls. The neuropsychological battery utilised included standard measures of cognition, such as the WAIS-R and WMS-R, and experimentally-derived computerised tests of memory. The same pattern of neuropsychological change was exhibited by patients with early DAT and by QD subjects who later fulfilled standard criteria for the disease. In both groups pronounced impairment of recent memory preceded deficits in language and visuospatial function. The progression of cognitive deterioration observed in DAT is likely to reflect the spread of neuropathology throughout the cortex. In view of these findings, the selection of appropriate neuropsychological measures for the detection and staging of early DAT is discussed. One computerised measure, the paired associate learning test, was found to be particularly efficacious in the prediction and early detection of DAT. The QD group performed at a similar level to normal controls when first assessed using the paired associate learning subtest. However, over the course of the study, 43% of the QD subjects exhibited significant deterioration in scores on this measure. All subjects who deteriorated on the computerised paired associate learning task met standard criteria for DAT at the conclusion of the study. Diagnosis of probable DAT was not predicted by any other demographic or psychometric variable. These findings are discussed in terms of the special sensitivity of the associate learning paradigm to the neuropathology of Alzheimer's disease.
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ItemNeuropsychological evidence for cognitive impairment in obsessive-compulsive disorder: relationship with clinical symptomatology( 1999)Neuropsychological studies of obsessive-compulsive (OCD) disorder yield diverging results. Purcell, Maruff, Kyrios & Pantelis (1998a; 1998b) examined cognitive function in a group of patients with OCD, and found specific deficits in spatial working memory, spatial recognition memory, and motor execution. However, no relationships were identified between cognitive impairment and obsessive-compulsive (OC) symptoms. The present study investigated the nature of cognitive impairments in a large sample of patients with OCD and explored the relationship between cognitive impairments, obsessive-compulsive symptoms, and treatment outcome. Study 1 showed that patients with OCD exhibit specific impairments in spatial working memory, spatial span, spatial recognition, attentional set shifting, and motor slowing. This study replicated earlier findings by Purcell et al. (1998a; 1998b) and is consistent with a neurobiological model of OCD which implicates dysfunction in frontal and subcortical brain regions. Study 2 found that levels of OC symptoms in the entire group were not correlated with cognitive impairments. However, when patients were classified according to their predominant symptom subtype, cognitive impairments were greatest in those classified as ‘checkers’. This suggests that cognitive impairment is related to type of obsessive-compulsive symptoms. To determine whether cognitive impairment was secondary to OC symptoms, neuropsychological assessment was repeated in a subgroup of patients with OCD who had significantly reduced symptom levels following cognitive-behavioural group treatment. Despite the symptom reduction, no improvement in cognitive function was found, apart from on one measure of spatial working memory. Results suggest that cognitive impairment in OCD may be more basic to the disorder, rather than arising as a consequence of the obsessive-compulsive symptoms per se. These results expand the body of research exploring neuropsychological function in OCD, and provide the first exploration of the relationship between cognitive impairment, OCD subgroups, OC symptoms, and treatment outcome.