Spatial and Ocular Trajectories for the Early Diagnosis of Alzheimer's Disease.

Spatial navigation is a high-level cognitive function that enables humans to orientate themselves and move around in space by constructing a mental representation of the environment. It is particularly interesting because it involves numerous neural networks, linked to proprioception and vision, for example. Despite the versatility of this cognitive function, spatial navigation is little studied clinically, although changes in spatial planning and navigation strategies have been associated with many brain disorders, including Alzheimer's disease (Coughlan et al., 2018). This may be explained in view of the neuropsychological tests currently in use, which do not effectively assess spatial navigation disorders. In addition, many non-pathological parameters - in particular socio-demographic and lifestyle - (Wolbers \& Hegarty, 2010; Coutrot et al., 2018) affect spatial navigation performance. Separating the pathological component from these non-pathological factors in spatial navigation can be challenging. In this context, Sea Hero Quest (SHQ) has been developed (Coutrot et al., 2018; Spiers et al., 2021) as an international-scale cognitive spatial navigation task that holds great promise for assessing spatial navigation performance during normal and pathological ageing. SHQ is a video game that implements classic tasks from the spatial cognition literature, and has enabled the trajectories of 4 million players with varied socio-demographic profiles to be collected. In addition to the direct measurement of spatial displacements, eye movements, measured by eye-tracking, provide additional information on the cognitive processes associated with visual attention. The analysis of eye movements can provide valuable information about the strategies employed by humans during spatial navigation (Zhu et al., eLife 2023). While it is well known that normal ageing and pathological ageing (e.g. in the context of Alzheimer's disease) affect performance in simple spatial navigati