Navigational cue effects in Alzheimer's disease and posterior cortical atrophy

Abstract

ObjectiveDeficits in spatial navigation are characteristic and disabling features of typical Alzheimer's disease (tAD) and posterior cortical atrophy (PCA). Visual cues have been proposed to mitigate such deficits; however, there is currently little empirical evidence for their use.MethodsThe effect of visual cues on visually guided navigation was assessed within a simplified real‐world setting in individuals with tAD (n = 10), PCA (n = 8), and healthy controls (n = 12). In a repeated‐measures design comprising 36 trials, participants walked to a visible target destination (an open door within a built environment), with or without the presence of an obstacle. Contrast and motion‐based cues were evaluated; both aimed to facilitate performance by applying perceptual changes to target destinations without carrying explicit information. The primary outcome was completion time; secondary outcomes were measures of fixation position and walking path directness during consecutive task phases, determined using mobile eyetracking and motion capture methods.ResultsResults illustrate marked deficits in patients’ navigational ability, with patient groups taking an estimated two to three times longer to reach target destinations than controls and exhibiting tortuous walking paths. There were no significant differences between tAD and PCA task performance. Overall, patients took less time to reach target destinations under cue conditions (contrast‐cue: 11.8%; 95% CI: [2.5, 20.3]) and were more likely initially to fixate on targets.InterpretationThe study evaluated navigation to destinations within a real‐world environment. There is evidence that introducing perceptual changes to the environment may improve patients’ navigational ability.

Impairments of auditory scene analysis in posterior cortical atrophy

“…Posterior cortical atrophy (PCA) is conventionally defined as a syndrome characterized by progressive impairment of higher visual function, in particular visuoperceptual and visuospatial skills, often designated the 'visual variant' of Alzheimer's disease (Benson et al, 1988;Crutch et al, 2017). Patients with PCA have particular difficulty interpreting and navigating 'busy', dynamic visual environments requiring parsing of multiple objects distributed in space (Shakespeare et al, 2013;Yong et al, 2018). Posterior cortical functions such as calculation, spelling and praxis are also affected in PCA (Benson et al, 1988;Crutch et al, 2017), along with other cognitive domains including language (Crutch et al, 2013), episodic memory (Ahmed et al, 2018), working memory (Trotta et al, 2019), executive functioning (Putcha et al, 2018), and visuo-vestibular integration (Crutch et al, 2018).…”

Detection and localisation of hesitant steps in people with Alzheimer's disease navigating routes of varying complexity

“…Controls were clearly able to anticipate the corners and walked with an efficient smooth path around the corners, but some participants in the dementia groups did not demonstrate the same anticipation. Either they were not able to efficiently interpret or act on the visual information, due to low visual orientation or visuomotor/visual processing impairments, or were unable to predict layouts of routes due to diminished topographical processing, spatial memory and/or executive function [26]. Future investigations might explore the relationship between gait dynamics, spatial memory and route learning abilities.…”

“…It is therefore particularly beneficial to be able to use standardised algorithms to process step data. In the context of research into dementia friendly environments, the effects of perceptual environmental variables, such as lighting, visual cues and clutter on patient navigation can be evaluated in a variety of scenarios [26].…”

A systematic review of atypical Alzheimer's disease including behavioural and psychological symptoms

“…Clinical manifestations PCA is a progressive neurodegenerative disease characterized by visuospatial or visuoperceptual symptoms with relative sparing of memory (see Table 3). [65][66][67][68][69][70][71] PCA patients could have significant impairment of everyday skills and self-care. 72 Patients often complain of having blurred or obscured vision.…”

“…113 In another study, Yong et al demonstrated that the use of visual cues can improve the ability of PCA patients to reach another destination in a closed-space setting. 70…”