title: Impaired allocentric spatial memory underlying topographical disorientation.
abstract: The cognitive processes supporting spatial navigation are considered in the context of a patient (CF) with possible very early Alzheimer's disease who presents with topographical disorientation. Her verbal memory and her recognition memory for unknown buildings, landmarks and outdoor scenes was intact, although she showed an impairment in face processing. By contrast, her navigational ability, quantitatively assessed within a small virtual reality (VR) town, was significantly impaired. Interestingly, she showed a selective impairment in a VR object-location memory test whenever her viewpoint was shifted between presentation and test, but not when tested from the same viewpoint. We suggest that a specific impairment in locating objects relative to the environment rather than relative to the perceived viewpoint (i.e. allocentric rather than egocentric spatial memory) underlies her topographical disorientation. We discuss the likely neural bases of this deficit in the light of related studies in humans and animals, focusing on the hippocampus and related areas. The specificity of our test indicates a new way of assessing topographical disorientation, with possible application to the assessment of progressive dementias such as Alzheimer's disease.
authors.affiliation: Institute of Cognitive Neuroscience, University College London, 17 Queen Square, London WC1N 3AR, UK. N.Burgess@ucl.ac.uk
authors.forename: Neil
authors.initials: N
authors.lastname: Burgess
authors.forename: Iris
authors.initials: I
authors.lastname: Trinkler
authors.forename: John
authors.initials: J
authors.lastname: King
authors.forename: Angus
authors.initials: A
authors.lastname: Kennedy
authors.forename: Lisa
authors.initials: L
authors.lastname: Cipolotti
mesh_terms: D000203:Activities of Daily Living / Q000523:psychology; D000368:Aged; D000544:Alzheimer Disease / Q000175:diagnosis / Q000503:physiopathology* / Q000523:psychology*; D000818:Animals; D004185:Disability Evaluation; D018450:Disease Progression; D042241:Early Diagnosis; D005260:Female; D006624:Hippocampus / Q000473:pathology / Q000503:physiopathology*; D006801:Humans; D008568:Memory / Q000502:physiology; D008569:Memory Disorders / Q000175:diagnosis / Q000503:physiopathology* / Q000523:psychology*; D008875:Middle Aged; D008959:Models, Neurological; D009483:Neuropsychological Tests; D009949:Orientation / Q000502:physiology; D013028:Space Perception / Q000502:physiology; D014705:Verbal Behavior / Q000502:physiology