Age-related differences in electrophysiological correlates of visuospatial reorientation

Spatial navigation abilities decline with age, affecting older adults' quality of life. Recent studies revealed a specific impairment in landmark-based reorientation, linked to changes in scene-selective brain regions' activity. While functional magnetic resonance imaging studies suggest increased activity in these regions in older adults, more detailed investigation of brain dynamics associated with visuospatial processing is warranted. We analyzed event-related potentials (ERPs) and event-related spectral perturbations recorded from electrodes over scene-selective regions. Twenty-eight young adults and 28 older adults performed a desktop-based reorientation task using objects as landmarks, contrasted with a passive scene perception task. Older adults showed reduced reorientation performance along with increased latencies of early cortical markers of visual processing in scene-selective regions, suggesting that navigational deficits may result from delayed processing of visuospatial information. Decreasing landmark size, and thus increasing perceptual difficulty, impaired performance in both age groups, but only resulted in a delayed P1 component in older adults, suggesting an age-related delayed early discrimination of smaller landmarks. Interestingly, by contrasting the reorientation task with a passive scene perception task, we were able to dissociate the age-related effect over the perception and the use of objects as landmarks. Our results suggest that most of the differences reported for neural markers of reorientation were already present in a passive scene perception task, highlighting the importance of accounting for age-related differences in scene perception when investigating deficits in visuospatial reorientation. When these differences in passive perception were accounted for using regression-based ERP, our results indicated that young adults showed increased neural markers of attentional resources allocated to the reorientation task, as indicated by an increased P1 amplitude. On the other hand, older adults exhibited increased N1 amplitude associated with <i>theta</i> activity during reorientation, suggesting that they might rely on more extensive neural resources to process visual objects, only when using them as landmarks. These findings emphasize the need to dissociate age-related changes in early perceptual processing from those affecting higher-order visuo-spatial mechanisms and suggest that age-related differences in scene processing may underpin some navigational deficits in older adults.