Preserved capacity for scene construction and shifts in perspective after hippocampal lesions

The hippocampus has long been recognized as important for the formation of long-term memory. Recent work has suggested that the hippocampus might also be important for certain kinds of spatial operations, as in constructing scenes, shifting perspective, or perceiving the geometry of scenes and their boundaries. We explored this proposal using a task similar to one used previously that related hippocampal activity to scenes and their boundaries. In our study, participants viewed scenes from above that displayed walls and towers. After viewing each scene, participants saw a scene from ground level and judged whether it was the same as or different from the scene just presented. The number of towers and walls in each scene was manipulated so that it was possible to assess how the structure of the scene affected performance. Patients with hippocampal lesions performed similarly to controls in all task conditions and had no special difficulty as a function of the layout of a scene and its boundaries. In contrast, a patient with large medial temporal lobe (MTL) lesions was impaired. Taken together, our findings suggest that the hippocampus is not needed for scene construction, shifts in perspective, or perceiving the geometry of scenes. The impairment associated with large MTL lesions may result from damage in or near parahippocampal cortex.