{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,30]],"date-time":"2026-09-30T13:13:09Z","timestamp":1790773989371,"version":"4.1.0"},"reference-count":46,"publisher":"Wiley","issue":"2","license":[{"start":{"date-parts":[[2021,12,10]],"date-time":"2021-12-10T00:00:00Z","timestamp":1639094400000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["physoc.onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["The Journal of Physiology"],"published-print":{"date-parts":[[2022,1]]},"abstract":"<jats:sec><jats:title>Abstract<\/jats:title><jats:p>There is increasing theoretical and empirical support for the brain combining multisensory information to determine the direction of gravity and hence uprightness. A fundamental part of the process is the spatial transformation of sensory signals between reference frames: eye\u2010centred, head\u2010centred, body\u2010centred, etc. The question \u2018Am I the right way up?\u2019 posed by a patient with posterior cortical atrophy (PCA) suggests disturbances in upright perception, subsequently investigated in PCA and typical Alzheimer's disease (tAD) based on what looks or feels upright. Participants repeatedly aligned to vertical a rod presented either visually (visual\u2010vertical) or haptically (haptic\u2010vertical). Visual\u2010vertical involved orienting a projected rod presented without or with a visual orientation cue (circle, tilted square (\u00b118\u00b0)). Haptic\u2010vertical involved orientating a grasped rod with eyes closed using a combination of side (left, right) and hand (unimanual, bimanual) configurations. Intraindividual uncertainty and bias defined verticality perception. Uncertainty was consistently greater in both patient groups than in control groups, and greater in PCA than tAD. Bias in the frontal plane was strongly directionally affected by visual cue tilt (visual\u2010vertical) and grip side (haptic\u2010vertical). A model was developed that assumed verticality information from multiple sources is combined in a statistically optimal way to produce observed uncertainties and biases. Model results suggest the mechanism that spatially transforms graviceptive information between body parts is disturbed in both patient groups. Despite visual dysfunction being typically considered the primary feature of PCA, disturbances were greater in PCA than tAD particularly for haptic\u2010vertical, and are considered in light of posterior parietal vulnerability.\n<jats:boxed-text content-type=\"graphic\" position=\"anchor\"><jats:graphic xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" mimetype=\"image\/png\" position=\"anchor\" specific-use=\"enlarged-web-image\" xlink:href=\"graphic\/tjp14912-gra-0001-m.png\"><jats:alt-text>image<\/jats:alt-text><\/jats:graphic><\/jats:boxed-text><\/jats:p><\/jats:sec><jats:sec><jats:title>Key points<\/jats:title><jats:p><jats:list list-type=\"bullet\">\n<jats:list-item><jats:p>The perception of upright requires accurate and precise estimates of orientation based on multiple noisy sensory signals.<\/jats:p><\/jats:list-item>\n<jats:list-item><jats:p>The question \u2018Am I the right way up?\u2019 posed by a patient with posterior cortical atrophy (PCA; purported \u2018visual variant Alzheimer's\u2019) suggests disturbances in the perception of upright.<\/jats:p><\/jats:list-item>\n<jats:list-item><jats:p>What looks or feels upright in PCA and typical Alzheimer's disease (tAD) was investigated by asking participants to repeatedly align to vertical a rod presented visually (visual\u2010vertical) or haptically (haptic\u2010vertical).<\/jats:p><\/jats:list-item>\n<jats:list-item><jats:p>PCA and tAD groups exhibited not only greater perceptual uncertainty than controls, but also exaggerated bias induced by tilted visual orientation cues (visual\u2010vertical) and grip side (haptic\u2010vertical). When modelled, these abnormalities, which were particularly evident in PCA haptic\u2010vertical performance, were compatible with disruption of a mechanism that spatially transforms verticality information between body parts.<\/jats:p><\/jats:list-item>\n<jats:list-item><jats:p>The findings suggest an important role of posterior parietal cortex in verticality perception, and have implications for understanding spatial disorientation in dementia.<\/jats:p><\/jats:list-item>\n<\/jats:list><\/jats:p><\/jats:sec>","DOI":"10.1113\/jp282289","type":"journal-article","created":{"date-parts":[[2021,11,29]],"date-time":"2021-11-29T02:49:59Z","timestamp":1638154199000},"page":"373-391","update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":17,"title":["Altered visual and haptic verticality perception in posterior cortical atrophy and Alzheimer's disease"],"prefix":"10.1113","volume":"600","author":[{"given":"Brian L.","family":"Day","sequence":"first","affiliation":[{"name":"Department of Clinical and Movement Neurosciences UCL Queen Square Institute of Neurology  London UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Dilek","family":"Ocal","sequence":"additional","affiliation":[{"name":"Dementia Research Centre Department of Neurodegenerative Disease UCL Queen Square Institute of Neurology University College London  London UK"},{"name":"Department of Neurophysics Max Planck Institute for Human Cognitive and Brain Sciences  Leipzig DE"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Amy","family":"Peters","sequence":"additional","affiliation":[{"name":"Department of Clinical and Movement Neurosciences UCL Queen Square Institute of Neurology  London UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5513-5058","authenticated-orcid":false,"given":"Matthew J.","family":"Bancroft","sequence":"additional","affiliation":[{"name":"Department of Clinical and Movement Neurosciences UCL Queen Square Institute of Neurology  London UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"David","family":"Cash","sequence":"additional","affiliation":[{"name":"Dementia Research Centre Department of Neurodegenerative Disease UCL Queen Square Institute of Neurology University College London  London UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Diego","family":"Kaski","sequence":"additional","affiliation":[{"name":"Department of Clinical and Movement Neurosciences UCL Queen Square Institute of Neurology  London UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sebastian J.","family":"Crutch","sequence":"additional","affiliation":[{"name":"Dementia Research Centre Department of Neurodegenerative Disease UCL Queen Square Institute of Neurology University College London  London UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9708-3599","authenticated-orcid":false,"given":"Keir X. 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