Bird, C.; (2007) Medial temporal lobe contributions to visuospatial memory and cognition. Doctoral thesis , University of London.

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Abstract

The contributions of human medial temporal lobe (MTL) structures to perceiving and remembering visuospatial features of the environment were investigated from the perspective of human cognitive neuropsychology. The experimental chapters focussed on three main issues: the contribution of the right-sided MTL to spatial awareness the roles of the right MTL and hippocampus in spatial and non-spatial scene perception and memory and the role of the hippocampus in anterograde memory for different types of memoranda. Visual neglect (a failure of spatial awareness), was investigated after lesions of the right medial occipitotemporal lobe. Lesion analyses and diffusion tensor imaging demonstrated that the lesions associated with neglect interrupted a white matter pathway connecting the parahippocampal gyrus with the parietal lobe. The interaction of these areas may be critical to subserve normal spatial awareness. Perception and short-term retention of spatial and non-spatial aspects of visual scenes were investigated using a new task - the 4 Mountains Test. Right MTL damage impaired both spatial perception and memory. Hippocampal damage impaired spatial memory but had little impact on scene perception. Damage to these areas did not affect non-spatial perception or memory, suggesting a role for the hippocampus in the short-term retention of allocentric spatial information. A rather similar pattern of performance was documented in patients with possible Alzheimer's disease. The role of the hippocampus in anterograde memory was investigated in two patients using recognition tests for words, scenes and faces. Receiver operating characteristics analyses were used to assess the contribution of recollection and familiarity to performance. Hippocampal damage impacted upon scene and word recognition but not face recognition. In terms of scene recognition, the hippocampus may be critical to make recognition judgements based on both recollection and highly confident feelings of familiarity.

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