Abstract
Spatial navigation involves multiple cognitive processes including multisensory integration, visuospatial coding, memory, and decision-making. These functions are mediated by the interplay of cerebral structures that can be broadly separated into a posterior network (subserving visual and spatial processing) and an anterior network (dedicated to memory and navigation planning). Within these networks, areas such as the hippocampus (HC) are known to be affected by aging and to be associated with cognitive decline and navigation impairments. However, age-related changes in brain connectivity within the spatial navigation network remain to be investigated. For this purpose, we performed a neuroimaging study combining functional and structural connectivity analyses between cerebral regions involved in spatial navigation. Nineteen young (μ = 27 years, σ = 4.3; 10 F) and 22 older (μ = 73 years, σ = 4.1; 10 F) participants were examined in this study. Our analyses focused on the parahippocampal place area (PPA), the retrosplenial cortex (RSC), the occipital place area (OPA), and the projections into the visual cortex of central and peripheral visual fields, delineated from independent functional localizers. In addition, we segmented the HC and the medial prefrontal cortex (mPFC) from anatomical images. Our results show an age-related decrease in functional connectivity between low-visual areas and the HC, associated with an increase in functional connectivity between OPA and PPA in older participants compared to young subjects. Concerning the structural connectivity, we found age-related differences in white matter integrity within the navigation brain network, with the exception of the OPA. The OPA is known to be involved in egocentric navigation, as opposed to allocentric strategies which are more related to the hippocampal region. The increase in functional connectivity between the OPA and PPA may thus reflect a compensatory mechanism for the age-related alterations around the HC, favoring the use of the preserved structural network mediating egocentric navigation. Overall, these findings on age-related differences of functional and structural connectivity may help to elucidate the cerebral bases of spatial navigation deficits in healthy and pathological aging.
Highlights
Spatial navigation represents one of the most fundamental activities of daily life and it requires the integration of multiple processes
We focused on how functional and structural connectivity differ between young and older groups within key structures involved in navigation: the medial prefrontal cortex (mPFC), the HC, and the scene-selective regions (PPA, retrosplenial cortex (RSC), and occipital place area (OPA))
Associated with these changes between visual and hippocampal regions, we found a significant increase in the functional connectivity between OPA and parahippocampal place area (PPA) regions in the left hemisphere of older adults (Figures 1A,C; see Supplementary Table S2 for detailed statistics)
Summary
Spatial navigation represents one of the most fundamental activities of daily life and it requires the integration of multiple processes These processes include the perception of spatial information from a variety of sensory cues, the creation and maintenance of spatial representations in memory, and the manipulation of these representations to guide navigational behavior (Wolbers and Hegarty, 2010; Julian et al, 2018). These spatial navigation abilities are mediated by numerous cerebral regions across the brain (Burgess, 2008; Spiers and Barry, 2015). The medial prefrontal cortex (mPFC) plays a key role in maintaining useful information in working memory and in selecting the most appropriate navigational strategy for the complexity of the task at hand (Wolbers et al, 2007; Spiers and Gilbert, 2015; Chrastil et al, 2017; Ito, 2018)
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