Effects of lighting variability on locomotion in posterior cortical atrophy

Abstract

Introduction Clinical reports describe patients with Alzheimer's disease (AD) exhibiting atypical adaptive walking responses to the visual environment; however, there is limited empirical investigation of such behaviors or factors modulating their expression. We aim to evaluate effects of lighting‐based interventions and clinical presentation (visual‐ vs memory‐led) on walking function in participants with posterior cortical atrophy (PCA) and typical AD (tAD). Methods Participants with PCA (n = 10), tAD (n = 9), and healthy controls (n = 12) walked to visible target destinations under different lighting conditions within two pilot repeated‐measures design investigations (Experiment 1: 32 trials per participant; Experiment 2: 36 trials per participant). Participants walked to destinations with the floorpath interrupted by shadows varying in spatial extent (Experiment 1: no, medium, high shadow) or with different localized parts of the environment illuminated (Experiment 2: target, middle, or distractor illuminated). The primary study outcome for both experimental tasks was completion time; secondary kinematic outcomes were proportions of steps identified as outliers (Experiment 1) and walking path directness (Experiment 2). Results In Experiment 1, PCA participants overall demonstrated modest reductions in time taken to reach destinations when walking to destinations uninterrupted by shadows compared to high shadow conditions (7.1% reduction [95% confidence interval 2.5, 11.5; P = .003]). Experiment 2 found no evidence of differences in task performance for different localized lighting conditions in PCA participants overall. Neither experiment found evidence of differences in task performance between conditions in tAD or control participants overall. Completion time in both patient groups was longer relative to controls, and longer in PCA relative to tAD groups. Discussion Findings represent a quantitative characterization of a clinical phenomenon involving patients misperceiving shadows, implicating dementia‐related cortico‐visual impairments. Results contribute to evidence‐based design guidelines for dementia‐friendly environments.

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“…This could be because PCA affects visual processing more than tAD, and therefore the effects of this disease are more prominent in a trial such as this. This trend has also been identified by previous research done in the same program of work at Pedestrian Accessibility Movement Environment Laboratory (PAMELA), which found that participants with early stage PCA performed worse than people with tAD (Yong et al, 2020). Therefore, because the gait of participants with is more easily distinguishable from "normal" gait than the gait of participants with tAD, the model does not confuse PCA with controls as often as it confuses tAD with controls.…”

“…Secondly, while some previous studies have analyzed different types of dementia (Mc Ardle et al, 2020), previous studies ignore the differences between types of dementia and either focus on one type of dementia (Wittwer et al, 2013;Cedervall et al, 2014;Callisaya et al, 2017) or consider dementia without looking at its type (Marquis et al, 2002;Wang et al, 2006). Furthermore, to our knowledge, gait of people with PCA has only been analyzed by previous research in this line of investigation (Carton et al, 2016;Ocal et al, 2017;Yong et al, 2018Yong et al, , 2020McCarthy et al, 2019;McCarthy et al, Unpublished 1 ). This research has found that some patients with dementia show a consistent pattern of hesitation (which can be identified from step times) when navigating complex routes (McCarthy et al, 2019;Yong et al, 2020).…”

“…Furthermore, to our knowledge, gait of people with PCA has only been analyzed by previous research in this line of investigation (Carton et al, 2016;Ocal et al, 2017;Yong et al, 2018Yong et al, , 2020McCarthy et al, 2019;McCarthy et al, Unpublished 1 ). This research has found that some patients with dementia show a consistent pattern of hesitation (which can be identified from step times) when navigating complex routes (McCarthy et al, 2019;Yong et al, 2020). However, it was not possible within that task to identify patterns which could be used for predictive purposes.…”

“…Previous lab-based research has demonstrated differences in gait parameters such as step-time and walking speed between people with dementia and age-matched controls (Marquis et al, 2002;Waite et al, 2005;Wang et al, 2006;Verghese et al, 2007;Cedervall et al, 2014;Rosso et al, 2017). These studies indicate that the decline is linked to both phenotype and stage of the disease (Allali et al, 2016;Castrillo et al, 2016;Del Campo et al, 2016;McCarthy et al, 2019;Yong et al, 2020). Furthermore, a noticeable decline in gait is thought to predate other cognitive decline (Hall et al, 2000).…”

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“…through digital presentation). Patients may exhibit difficulties with navigation, becoming lost in familiar environments and negotiating escalators, stairs and flooring with reflective surfaces, patterns and shadows [33]. The above difficulties may relate to early visuospatial and visuoperceptual abnormalities owing to parieto-occipital and occipito-temporal atrophy [23] along with more basic visual dysfunction arising from occipital damage [34,35].…”