Reduced navigation ability has been associated with advanced age in general and particularly with Alzheimer's disease (AD). Navigation difficulties can be devastating to an individual's self-reliance, and such problems can even be dangerous, particularly while driving. Research suggests that such age related difficulties arise specifically from deficits in the ability to create structured cognitive maps of environments from traveling around in them. Theories of how these mental maps are constructed during navigation are sorely needed to design responses to older adults' difficulties with getting lost. Here we test a novel proposal constraining how mental maps are built up from navigation experience and how mental map construction changes with age. Research suggests that spatial representations and spatial memory in general, are organized into chunks; certain locations are grouped together in memory. Several factors, such as temporal and spatial proximity and salient physical features of the environment have been identified as important in determining what locations get chunked together. However, little work has been done to identify specific cognitive and neural mechanisms by which spatial memory is organized. We propose that temporal segmentation of experience into episodes, or events, is an important factor in determining the structure of spatial memory. Therefore, improving temporal encoding could improve spatial memory. In these experiments, participants will view short first person movies of actors navigating through particular environments (e.g., buildings). In some cases, participants will segment the movies into spatial regions or events, and in others functional magnetic imaging (fMRI) will be used to monitor brain activity during movie viewing. After movie viewing, spatial memory for the navigated environments will be measured to test the following hypotheses: 1) Spatial and temporal segmentation during navigation affects later memory for the navigated space. 2) Age related declines in spatial and temporal segmentation mechanisms are associated with poorer spatial memory. 3) Phasic activity in spatially sensitive brain regions is disrupted in older adult, and this disruption is associated with spatial memory impairment. Successful completion of this research will open up a new set of cognitive and neural mechanisms as targets for researchers and clinicians working to address the important problem of age related navigation difficulty. Theoretically motivated measures of structure in spatial memory may prove particularly valuable for diagnosing navigation difficulties associated with early-stage dementia. If age-related navigating difficulties are mediated by temporal segmentation impairments, this will provide a novel target for intervention. PUBLIC HEALTH RELEVANCE: Navigation difficulties associated with normal aging, and especially with age-related dementia, can be devastating to an individual's self-reliance, and such problems can even be dangerous, particularly while driving. This work will examine how the structure of spatial memory is determined and how important aspects of that structure change as we age. Successful completion of this research will open up a new set of cognitive and neural mechanisms as targets for researchers and clinicians working to address the important problem of age related navigation difficulty.