Hippocampal Involvement in Visuo-spatial Cognition: Cushing's Disease as a Model for Hippocampal Dysfunction
Brown, Matthew S.
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The majority of research into the role of the hippocampus has focused on its function in men1ory. Recent research, however, has indicated possible hippocampal involvement in forms of visuo-spatial cognition. The present study attempted to elucidate further the possibility of a hippocampal role in visuo-spatial cognition. Elevated levels of the glucocorticoid hormone cortisol have been shown to inflict localized damage (measured by reduction in structure volume) to the hippocampus without confounding diffuse brain damage. Cushing's disease is a highly complex endocrine disorder is characterized by chronic elevation of the corticosteroid hormone cortisol. This chronic exposure to elevated levels of cortisol makes Cushing's disease a good model to study localized hippocampal damage and dysfunction. For this reason. the present study investigated the visuo-spatial deficits in 33 patients with Cushing's disease. Visuo-spatial ability was measured in terms of performance on three neuropsychological measures of visuo-spatial ability: the Block Design, Picture Arrangement and Picture Completion subsets of the W AIS-R. The primary intent of the present study was to demonstrate a hippocampal role in complex visuo-spatial cognition, a cognitive process separate from the already well-established hippocampal role in memory. It was hypothesized that hippocampal formation volumes (HFV) as measured by magnetic resonance imaging would correlate with deficits in the tasks of visuo-spatial ability. Results indicated significant correlations between HFV and deficits on visuo-spatial tasks, providing further evidence for a hippocampal role in visuo-spatial cognition.