TY - JOUR T1 - 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 JF - The Journal of Neuroscience JO - J. Neurosci. SP - 5901 LP - 5908 DO - 10.1523/JNEUROSCI.1346-04.2004 VL - 24 IS - 26 AU - Boyer D. Winters AU - Suzanna E. Forwood AU - Rosemary A. Cowell AU - Lisa M. Saksida AU - Timothy J. Bussey Y1 - 2004/06/30 UR - http://www.jneurosci.org/content/24/26/5901.abstract N2 - 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. Figure 1. Illustration of the phases of the spontaneous object recognition task as run in the Y-shaped apparatus. The nearest wall of the apparatus appears transparent for illustrative purposes. The guillotine door is shown raised. At the beginning of each phase, the rat is released from the start box when the experimenter manually raises the guillotine door. In the sample phase, the rat is exposed to identical versions of the same object, one at the end of each exploration arm. At the end of the sample phase, a variable retention delay is imposed. After the retention delay, the rat is reintroduced to the apparatus, which now contains an identical copy of the sample object at the end of one exploration arm and a novel object at the end of the other arm. Normal rats spend more time exploring the novel object. ER -