Memory consolidation of landmarks in good navigators

Abstract

Landmarks play an important role in successful navigation. To successfully find your way around an environment, navigationally relevant information needs to be stored and become available at later moments in time. Evidence from functional magnetic resonance imaging (fMRI) studies shows that the human parahippocampal gyrus encodes the navigational relevance of landmarks. In the present event-related fMRI experiment, we investigated memory consolidation of navigationally relevant landmarks in the medial temporal lobe after route learning. Sixteen right-handed volunteers viewed two film sequences through a virtual museum with objects placed at locations relevant (decision points) or irrelevant (nondecision points) for navigation. To investigate consolidation effects, one film sequence was seen in the evening before scanning, the other one was seen the following morning, directly before scanning. Event-related fMRI data were acquired during an object recognition task. Participants decided whether they had seen the objects in the previously shown films. After scanning, participants answered standardized questions about their navigational skills, and were divided into groups of good and bad navigators, based on their scores. An effect of memory consolidation was obtained in the hippocampus: Objects that were seen the evening before scanning (remote objects) elicited more activity than objects seen directly before scanning (recent objects). This increase in activity in bilateral hippocampus for remote objects was observed in good navigators only. In addition, a spatial-specific effect of memory consolidation for navigationally relevant objects was observed in the parahippocampal gyrus. Remote decision point objects induced increased activity as compared with recent decision point objects, again in good navigators only. The results provide initial evidence for a connection between memory consolidation and navigational ability that can provide a basis for successful navigation.