Schematic representations of local environmental space guide goal-directed navigation

To successfully navigate to a target, it is useful to be able to define its location at multiple levels of specificity. For example, the location of a favorite coffee mug can be described in terms of which room it is in, or in terms of where it is within the room. An appealing hypothesis is that these levels of description are retrieved from memory by accessing the same representation at progressively finer levels of granularity first remembering the general location of an object and then zooming in. Here we provide evidence for an alternative view, in which navigational behavior is guided by independent representations at multiple spatial scales. Subjects learned the locations of objects that were positioned within four visually distinct but geometrically similar buildings, which were in turn positioned within a broader virtual park. They were then tested on their knowledge of object location by asking them to navigate to the remembered location of each object. We examined errors during the test phase for confusions among geometrically analogous locations in different buildings that is, navigating to the right location in the wrong building. We observed that subjects frequently made these confusions, which are analogous to remembering a passage's location on the page of a book but not remembering the page that the passage is on. This suggests that subjects were recalling the object's local location without recalling its global location. Further manipulations across seven experiments indicated that geometric confusions were observed even between buildings that were not metrically identical as long as geometrical equivalence could be defined. However, removing the walls so that the larger environment was no longer divided into subspaces abolished these errors. Taken together, our results suggest that human spatial memory contains two separable representations of where an object can be found: (i) a schematic map of where an object lies with respect to local landmarks and boundaries; (ii) a representation of the identity and location of each local environment. (C) 2016 Elsevier B.V. All rights reserved.