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      Effects of lighting variability on locomotion in posterior cortical atrophy

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          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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          Most cited references41

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          The diagnosis of dementia due to Alzheimer's disease: Recommendations from the National Institute on Aging-Alzheimer's Association workgroups on diagnostic guidelines for Alzheimer's disease

          The National Institute on Aging and the Alzheimer's Association charged a workgroup with the task of revising the 1984 criteria for Alzheimer's disease (AD) dementia. The workgroup sought to ensure that the revised criteria would be flexible enough to be used by both general healthcare providers without access to neuropsychological testing, advanced imaging, and cerebrospinal fluid measures, and specialized investigators involved in research or in clinical trial studies who would have these tools available. We present criteria for all-cause dementia and for AD dementia. We retained the general framework of probable AD dementia from the 1984 criteria. On the basis of the past 27 years of experience, we made several changes in the clinical criteria for the diagnosis. We also retained the term possible AD dementia, but redefined it in a manner more focused than before. Biomarker evidence was also integrated into the diagnostic formulations for probable and possible AD dementia for use in research settings. The core clinical criteria for AD dementia will continue to be the cornerstone of the diagnosis in clinical practice, but biomarker evidence is expected to enhance the pathophysiological specificity of the diagnosis of AD dementia. Much work lies ahead for validating the biomarker diagnosis of AD dementia. Copyright © 2011. Published by Elsevier Inc.
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            The worldwide costs of dementia 2015 and comparisons with 2010

            Introduction In 2010, Alzheimer's Disease International presented estimates of the global cost of illness (COI) of dementia. Since then, new studies have been conducted, and the number of people with dementia has increased. Here, we present an update of the global cost estimates. Methods This is a societal, prevalence-based global COI study. Results The worldwide costs of dementia were estimated at United States (US) $818 billion in 2015, an increase of 35% since 2010; 86% of the costs occur in high-income countries. Costs of informal care and the direct costs of social care still contribute similar proportions of total costs, whereas the costs in the medical sector are much lower. The threshold of US $1 trillion will be crossed by 2018. Discussion Worldwide costs of dementia are enormous and still inequitably distributed. The increase in costs arises from increases in numbers of people with dementia and in increases in per person costs.
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              How to reliably estimate the tortuosity of an animal's path: straightness, sinuosity, or fractal dimension?

              The tortuosity of an animal's path is a key parameter in orientation and searching behaviours. The tortuosity of an oriented path is inversely related to the efficiency of the orientation mechanism involved, the best mechanism being assumed to allow the animal to reach its goal along a straight line movement. The tortuosity of a random search path controls the local searching intensity, allowing the animal to adjust its search effort to the local profitability of the environment. This paper shows that (1) the efficiency of an oriented path can be reliably estimated by a straightness index computed as the ratio between the distance from the starting point to the goal and the path length travelled to reach the goal, but such a simple index, ranging between 0 and 1, cannot be applied to random search paths; (2) the tortuosity of a random search path, ranging between straight line movement and Brownian motion, can be reliably estimated by a sinuosity index which combines the mean cosine of changes of direction with the mean step length; and (3) in the current state of the art, the fractal analysis of animals' paths, which may appear as an alternative and promising way to measure the tortuosity of a random search path as a fractal dimension ranging between 1 (straight line movement) and 2 (Brownian motion), is only liable to generate artifactual results. This paper also provides some help for distinguishing between oriented and random search paths, and depicts a general, comprehensive framework for analysing individual animals' paths in a two-dimensional space.
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                Author and article information

                Contributors
                keir.yong@ucl.ac.uk
                Journal
                Alzheimers Dement (N Y)
                Alzheimers Dement (N Y)
                10.1002/(ISSN)2352-8737
                TRC2
                Alzheimer's & Dementia : Translational Research & Clinical Interventions
                John Wiley and Sons Inc. (Hoboken )
                2352-8737
                07 October 2020
                2020
                : 6
                : 1 ( doiID: 10.1002/trc2.v6.1 )
                : e12077
                Affiliations
                [ 1 ] Dementia Research Centre Department of Neurodegenerative Disease UCL Queen Square Institute of Neurology London UK
                [ 2 ] Pedestrian Accessibility and Movement Environment Laboratory Department of Civil, Environmental and Geomatic Engineering Faculty of Engineering Science University College London London UK
                [ 3 ] Department of Medical Statistics Faculty of Epidemiology and Population Health London School of Hygiene & Tropical Medicine London UK
                [ 4 ] Centre for Medical Image Computing Department of Computer Science Faculty of Engineering Science University College London London UK
                Author notes
                [*] [* ] Correspondence

                Keir Yong, Dementia Research Centre, Box 16, National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, UK.

                E‐mail: keir.yong@ 123456ucl.ac.uk

                Article
                TRC212077
                10.1002/trc2.12077
                7539669
                06eecedf-8042-4d9b-9c8a-727c28362b0f
                © 2020 The Authors. Alzheimer's & Dementia: Translational Research & Clinical Interventions published by Wiley Periodicals, Inc. on behalf of Alzheimer's Association.

                This is an open access article under the terms of the http://creativecommons.org/licenses/by/4.0/ License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

                History
                : 10 March 2020
                : 10 July 2020
                : 28 July 2020
                Page count
                Figures: 3, Tables: 3, Pages: 11, Words: 6382
                Funding
                Funded by: Alzheimer's Research UK
                Funded by: Brain Research Trust , open-funder-registry 10.13039/501100000368;
                Funded by: The Wolfson Foundation
                Funded by: NIHR Queen Square Dementia Biomedical Research Unit
                Funded by: Alzheimer's Research UK Senior Research Fellowship
                Award ID: ART‐SRF2010‐3
                Award ID: ES/L001810/1
                Award ID: EP/M006093/1
                Categories
                Research Article
                Research Articles
                Custom metadata
                2.0
                2020
                Converter:WILEY_ML3GV2_TO_JATSPMC version:5.9.2 mode:remove_FC converted:07.10.2020

                alzheimer's disease,dementia,locomotion,posterior cortical atrophy,visual perception

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