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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

published_or_final_version / abstract / toc / Clinical Psychology / Master / Master of Social Sciences

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This thesis includes several studies investigating the right medial temporal-lobe contribution to memory for the location of objects in an array. Three arrays of toy objects were constructed and shown to be comparable in difficulty on the basis of tests with undergraduate students. These arrays were then employed as the test material for examining memory with tasks of immediate or delayed recall within a single trial, in addition to learning-to-criterion across multiple trials. Normal control subjects and patients with unilateral resection from the anterior temporal lobe were tested. The patients had undergone either selective amygdalo-hippocampectomy or anterior temporal lobectomy that either spared or largely invaded the hippocampal formation. The only groups showing impairment were those with large resections from the right hippocampal region; this deficit was noted on immediate recall, delayed recall, and incremental learning of the spatial arrays. In 75 of the patients tested, postoperative magnetic resonance scans were used to measure the extent of tissue remaining in the medial temporal-lobe structures; from multiple regression analyses, the extent of right hippocampus remaining was found to be the best predictor of array-learning performance. The notion that the hippocampus encodes spatial information in a map-like or allocentric manner (O'Keefe and Nadel, 1978) was explored by requiring normal control subjects and patients with unilateral temporal-lobe lesions to reconstruct the spatial arrays from a vantage-point other than that from which they had previously viewed the arrays. Contrary to prediction, the allocentric manipulation failed, in general, to elicit any additional impairment. Taken together, the results indicate that damage limited to the medial-temporal region in the right hemisphere is sufficient to disrupt memory for the location of objects. Within this region, the hippocampus appears to be the most critical structure for building, over suc

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