Age-related decline in visuo-spatial working memory is reflected by dorsolateral prefrontal activation and cognitive capabilities

Introduction: Visuo-spatial working memory (VSWM) performances undergo a decline throughout aging and are affected by the space in which the task is performed (reaching or navigational). Cerebral oxygenation and cognitive capabilities could explain this decline. We assessed the effects of age on cerebral oxygenation of the dorsolateral prefrontal cortex (dlPFC) in VSWM tasks in reaching and navigational space. We also assessed cognitive correlates of VSWM performance in each space. Method: Thirty-one (31) young adults (YA) and 24 healthy older adults (OA) performed a battery of neuropsychological tests and the electronic Corsi Block-tapping Test in reaching space (e-CBT) and in navigational space on the "Virtual Carpet" (VWCT). Participants were asked to memorize and recall a sequential pathway, progressively increasing from 2 to 9 blocks. Their span score reflected VSWM performance. The dlPFC oxygenation (oxyhaemoglobin: Delta O(2)Hb and deoxyhaemoglobin: Delta HHb) was measured by using functional Near-Infrared Spectroscopy (fNIRS) during the encoding of the sequential pathway in both tasks. Results: YA had higher span scores than OA in both spaces. We identified a significantly stronger decrease of Delta HHb in YA compared to OA during encoding in VWCT. OA also exhibited significantly lower cerebral oxygenation in VWCT compared to e-CBT. A decrease of Delta HHb was also associated with a better performance in VWCT. Finally, we identified the association of mental rotation and executive functions with VSWM performance in both tasks. Conclusion: VSWM performance and cerebral oxygenation during encoding are impacted by aging. Space in which the task was performed was found to be associated with different cognitive functions and revealed differences in cerebral oxygenation.