Age-related differences in spatial memory occur alongside reduced visual fMRI BOLD but preserved viewpoint-specific scene representations

Abstract

Current evidence suggests that older adults perform worse at tasks involving spatial memory and navigation, yet the underlying reasons remain unclear. Here, we tested the hypothesis that age-related declines in spatial memory stem from difficulties in recognizing spatial environments from rotated perspectives. Young and older adults underwent fMRI as they encoded virtual scenes which were later viewed either from the same or rotated perspective. Older adults were worse at identifying changes in these scenes, although the age effect was equally robust across perspective conditions. Neural specificity of scene representations was examined with the phenomenon of fMRI repetition adaptation. We predicted that young adults would show significant fMRI adaptation to the same but not rotated perspective, indicative of intact viewpoint specificity, while older adults show would adaptation effects to both. While analyses of raw fMRI BOLD produced results consistent with these predictions, follow-up analyses revealed a general attenuation of activity in older adults across both perspective conditions. Additionally, although older adults showed both lower fMRI BOLD and worse spatial memory, lower trial-wise BOLD was associated with better performance independent of age. This suggests that the variance associated with fMRI adaptation is reflective of two independent sources of variance: age and cognition. Our results suggest that age differences in spatial memory may manifest due to cognitive and neural factors that are shared across same and rotated perspectives, and thus they cannot be explained by a selective deficit in allocentric (viewpoint-independent) processing. Significance StatementIncreasing age is often associated with reduced spatial memory and navigation. Prior research suggests that age differences in spatial memory could be exacerbated by changes in perspective, possibly due to increased difficulties in the ability to construct allocentric (viewpoint-independent) representations from previously encoded egocentric perspectives. Here, we demonstrate that older adults are equally disadvantaged when recognizing layouts across same and rotated perspectives. FMRI analyses indicate that older age is associated with reduced fMRI BOLD in higher-level visual cortex across both perspective conditions, as opposed to altered specificity of perspective coding. Consequently, the present study challenges the notion that aging is associated with a selective decline in allocentric spatial memory and instead supports a more general age-related difficulty with scene processing.