Why senior adults get lost more frequently than younger adults.

Strang et al. identify the brain area whose degeneration with aging underlies the loss of our navigational abilities:

Highlights

•Grid-cell-like representations in human entorhinal cortex are compromised in old age 

•This effect is predominantly driven by a lack of representational stability over time 

•Path integration ability in old age is associated with grid-cell-like representations

Summary

A progressive loss of navigational abilities in old age has been observed in numerous studies, but we have only limited understanding of the neural mechanisms underlying this decline. A central component of the brain’s navigation circuit are grid cells in entorhinal cortex, largely thought to support intrinsic self-motion-related computations, such as path integration (i.e., keeping track of one’s position by integrating self-motion cues). Given that entorhinal cortex is particularly vulnerable to neurodegenerative processes during aging and Alzheimer’s disease, deficits in grid cell function could be a key mechanism to explain age-related navigational decline. To test this hypothesis, we conducted two experiments in healthy young and older adults. First, in an fMRI experiment, we found significantly reduced grid-cell-like representations in entorhinal cortex of older adults. Second, in a behavioral path integration experiment, older adults showed deficits in computations of self-position during path integration based on body-based or visual self-motion cues. Most strikingly, we found that these path integration deficits in older adults could be explained by their individual magnitudes of grid-cell-like representations, as reduced grid-cell-like representations were associated with larger path integration errors. Together, these results show that grid-cell-like representations in entorhinal cortex are compromised in healthy aging. Furthermore, the association between grid-cell-like representations and path integration performance in old age supports the notion that grid cells underlie path integration processes. We therefore conclude that impaired grid cell function may play a key role in age-related decline of specific higher-order cognitive functions, such as spatial navigation.