Neural correlates of topographic mental exploration: The impact of route versus survey perspective learning

There are two major sources of information to build a topographic represent ation of an environment, namely actual navigation within the environment (r oute perspective) and map learning (survey perspective). The aim of the pre sent work was to use positron emission tomography (PET) to compare the neur al substrate of the topographic representation built from these two modes. One group of subjects performed a mental exploration task in an environment learned from actual navigation (mental navigation task). Another group of subjects performed exploration in the same environment learned from a map ( mental map task). A right hippocampal activation common to both mental navi gation and mental map tasks was evidenced and may correspond the neural sub strate of a "dual-perspective" representation. The parahippocampal gyrus wa s additionally activated bilaterally during mental navigation only. These r esults suggest that the right hippocampus involvement would be sufficient w hen the representation incorporates essentially survey information while th e bilateral parahippocampal gyrus would be involved when the environment in corporates route information and includes "object" landmarks. The activatio n of a parietofrontal network composed of the intraparietal sulcus, the sup erior frontal sulcus, the middle frontal gyrus, and the pre-SMA. was observ ed in common for both mental navigation and mental map and is likely to ref lect the spatial mental imagery components of the tasks. (C) 2000 Academic Press.