title: Double dissociation between the effects of peri-postrhinal cortex and hippocampal lesions on tests of object recognition and spatial memory: heterogeneity of function within the temporal lobe.
abstract: It is widely believed that declarative memory is mediated by a medial temporal lobe memory system consisting of several distinct structures, including the hippocampus and perirhinal cortex. The strong version of this view assumes a high degree of functional homogeneity and serial organization within the medial temporal lobe, such that double dissociations between individual structures should not be possible. In the present study, we tested for a functional double dissociation between the hippocampus and peri-postrhinal cortex in a single experiment. Rats with bilateral excitotoxic lesions of either the hippocampus or peri-postrhinal cortex were assessed in tests of spatial memory (radial maze) and object recognition memory. For the latter, the spontaneous object recognition task was conducted in a modified apparatus designed to minimize the potentially confounding influence of spatial and contextual factors. A clear functional double dissociation was observed: rats with hippocampal lesions were impaired relative to controls and those with peripostrhinal cortex lesions on the spatial memory task, whereas rats with peri-postrhinal lesions were impaired relative to the hippocampal and control groups in object recognition. These results provide strong evidence in favor of heterogeneity and independence of function within the temporal lobe.
authors.affiliation: Department of Experimental Psychology, University of Cambridge, Cambridge CB2 3EB, United Kingdom. bdw23@cam.ac.uk
authors.forename: Boyer D
authors.initials: BD
authors.lastname: Winters
authors.forename: Suzanna E
authors.initials: SE
authors.lastname: Forwood
authors.forename: Rosemary A
authors.initials: RA
authors.lastname: Cowell
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Saksida
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Bussey
mesh_terms: D000818:Animals; D001931:Brain Mapping; D005106:Exploratory Behavior / Q000187:drug effects / Q000502:physiology*; D006624:Hippocampus / Q000187:drug effects / Q000502:physiology*; D007051:Ibotenic Acid / Q000494:pharmacology; D008297:Male; D018782:Maze Learning / Q000187:drug effects / Q000502:physiology*; D008569:Memory Disorders / Q000209:etiology / Q000503:physiopathology*; D011939:Mental Recall / Q000187:drug effects / Q000502:physiology; D016202:N-Methylaspartate / Q000633:toxicity; D009498:Neurotoxins / Q000633:toxicity; D051381:Rats; D016037:Single-Blind Method; D013702:Temporal Lobe / Q000187:drug effects / Q000502:physiology*
chemical_list: D009498:Neurotoxins; D007051:Ibotenic Acid; D016202:N-Methylaspartate