Virtual navigation and scene exploration in early Alzheimer's disease

Abstract

AbstractBackgroundSpatial navigation deficits are present early in Alzheimer´s disease (AD) and could thus serve as an early cognitive marker of the disease. AD patients were shown to have altered scene exploration during spatial navigation as they overlook objects of interest. We aimed to evaluate the potential of a virtual spatial navigation task and eye‐tracking assessment to identify individuals with early AD and to differentiate them from those with cognitive deficit of other etiology.Methods48 participants: amnestic mild cognitive impairment (aMCI) with positive AD‐biomarkers (aMCI due to AD, n=14), aMCI with negative biomarkers (aMCI AD‐negative, n=8), mild AD dementia (n=9) and cognitively normal (CN) older adults (n=17) underwent clinical and neuropsychological evaluation, MRI brain scan, amyloid PET imaging, cerebrospinal fluid biomarker assessment and spatial navigation testing in a virtual realistic‐looking “Intersections” test. The test consisted of three tasks: i) egocentric “route repetition”, where participants repeated the route through a virtual city, ii) allocentric “route retracing”, where participants indicated their way back, and iii) allocentric “different approach direction” combined with eye‐tracking, where participants indicated their original position from a different perspective at each intersection with two same and two unique houses. Number of fixations and length of fixation of unique houses were analyzed.ResultsThe aMCI due to AD and mild AD dementia groups had lower scores in the egocentric “route repetition” and allocentric “route retracing” tasks compared to the CN (p<0.012) and aMCI AD‐negative (p<0.007) groups. There were no differences between the CN and aMCI AD‐negative groups in these tasks. The AD dementia group had lower scores in the allocentric “different approach direction” task compared to the CN group (p=0.027). Duration and number of fixations of unique landmarks in the “different approach direction” was similar across all groups that demonstrated higher number and longer duration of fixations regardless of the task performance (p<0.001).ConclusionThe egocentric and allocentric tasks from the virtual “Intersection” test reliably detect spatial navigation impairment typical for early stages of AD. Spatial navigation unlike scene exploration can differentiate individuals with aMCI due to AD from those with non‐AD etiology.