Depth Perception in Alzheimer's Disease

1996 ◽  
Vol 83 (3) ◽  
pp. 987-995 ◽  
Author(s):  
Mario F. Mendez ◽  
Monique M. Cherrier ◽  
Robert S. Meadows
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Depth Perception ◽  
Motion Parallax ◽  
Relative Size ◽  
Depth Cues ◽  
Visuospatial Deficits ◽  
Visuospatial Functions ◽  
Monocular Depth ◽  
Global Stereopsis

Abnormal depth perception contributes to visuospatial deficits in Alzheimer's disease. Disturbances in stereopsis, motion parallax, and the interpretation of static monocular depth cues may result from neuropathology in the visual cortex. We evaluated 15 patients with mild Alzheimer's disease and 15 controls matched for age, sex, and education on measures of local stereopsis (stereoscopic testing), global stereopsis (random dots), motion parallax (Howard-Dolman apparatus), and monocular depth perception by relative size, interposition, and perspective. Compared to controls, the patients were significantly impaired in over-all depth perception. This impairment was largely due to disturbances in local stereopsis and in the interpretation of depth from perspective, independent of other visuospatial functions. Patients with Alzheimer's disease have disturbed interpretation of monocular as well as binocular depth cues. This information could lead to optic interventions to improve their visual depth perception.

scholarly journals Relations between Neuropsychological and Cerebral Metabolic Asymmetries in Early Alzheimer's Disease

1985 ◽  
Vol 5 (2) ◽  
pp. 193-200 ◽  
Author(s):  
James V. Haxby ◽  
Ranjan Duara ◽  
Cheryl L. Grady ◽  
Neal R. Cutler ◽  
Stanley I. Rapoport
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Emission Tomography ◽  
Temporal Association ◽  
Healthy Controls ◽  
Lateral Asymmetry ◽  
Visuospatial Deficits ◽  
Positron Emission ◽  
Visuospatial Functions ◽  
Early Alzheimer’S Disease

Regional CMRglc (rCMRglc) values were determined with positron emission tomography (PET) in 10 patients with mild to moderate clinically diagnosed Alzheimer's disease (AD) and in 26 healthy controls. rCMRglc in frontal, parietal, and temporal association cortices were significantly more laterally asymmetrical in AD patients than in controls (p < 0.05). Furthermore, lateral asymmetry of rCMRglc in AD patients but not in the control subjects correlated significantly with asymmetry of language and visuospatial functions such that lower left than right rCMRglc was associated with relatively greater impairment of language and vice versa. The results demonstrate that discrepancies between language and visuospatial deficits in patients with early AD are related to asymmetrical reductions in cerebral cortical glucose metabolism.

scholarly journals Stereoscopic Depth Perception and Visuospatial Dysfunction in Alzheimer’s Disease

Healthcare ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 157
Author(s):  
Nam-Gyoon Kim ◽  
Ho-Won Lee
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Depth Perception ◽  
Disease Diagnosis ◽  
Depth Information ◽  
Processing Capacity ◽  
Visuospatial Deficits ◽  
Potential Marker ◽  
Patient Groups ◽  
Better Than

With visuospatial dysfunction emerging as a potential marker that can detect Alzheimer’s disease (AD) even in its earliest stages and with disturbance in stereopsis suspected to be the prime contributor to visuospatial deficits in AD, we assessed stereoscopic abilities of patients with AD and mild cognitive impairment (MCI). Whereas previous research assessing patients’ stereoacuity has yielded mixed results, we assessed patients’ capacity to process coarse disparities that can convey adequate depth information about objects in the environment. We produced two virtual cubes at two different distances from the observer by manipulating disparity type (absolute vs. relative), disparity direction (crossed vs. uncrossed) and disparity magnitude, then had participants judge the object that appeared closer to them. Two patient groups performed as well as, or even better than elderly controls, suggesting that AD patients’ coarse disparity processing capacity is capable of supporting common tasks involving reaching, grasping, driving, and navigation. Results may help researchers narrow down the exact cause(s) of visuospatial deficits in AD and develop and validate measures to assess visuospatial dysfunction in clinical trials and disease diagnosis.

Relative Height and Relative Size as Monocular Depth Cues in the Trapezoid

1966 ◽  
Vol 22 (1) ◽  
pp. 275-281 ◽  
Author(s):  
Bruce E. Dunn ◽  
Stuart W. Thomas
Keyword(s):  
Relative Size ◽  
Frontal Plane ◽  
Vertical Axis ◽  
Vertical Edge ◽  
Relative Height ◽  
Depth Cues ◽  
Horizontal Length ◽  
Monocular Depth Cues ◽  
Monocular Depth

Ss viewed trapezoids and made absolute judgments of their degree of tilt around a vertical axis. The trapezoids were equal in horizontal length but the ratio of their vertical edges was 15:16 or 13:16. The height in the frontal plane of the midpoint of the shorter vertical edge varied from above (positive) to below (negative) the midpoint height of the longer vertical edge. Two extremes in the type of function to expect were predicted on the basis of past experimentation and geometric considerations. It was found that as the relative midpoint height went from negative to positive, perceived tilt increased linearly except for a brief reversal in the 15:16 condition. Perceived tilt was shown to be greater, but with some overlap, for the 13:16 trapezoids.

Atypical presentations of Alzheimer’s disease

2017 ◽  
Author(s):  
Matthew Jones ◽  
Jennifer Thompson
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Early Onset ◽  
Memory Loss ◽  
Cortical Atrophy ◽  
Visuospatial Deficits ◽  
Word Finding ◽  
Appropriate Care ◽  
Early Onset Alzheimer’S Disease ◽  
Atypical Presentations

Alzheimer’s disease usually presents in older age with progressive episodic memory loss. Atypical presentations of Alzheimer’s disease occur and involve non-amnestic and early-onset forms of the disease. Posterior cortical atrophy (PCA) and logopenic progressive aphasia (lvPPA) are two well-described syndromes that are most commonly due to atypical presentations of Alzheimer’s disease. PCA is a higher-order disturbance of vision whilst lvPPA is characterized by hesitant speech with word-finding difficulties and problems with repetition of words and phrases. Early-onset Alzheimer’s disease presents before the age of 65 and typically consists of a constellation of progressive cortical deficits including language disturbance, apraxia, visuospatial deficits, and poor working memory. Alzheimer’s disease may rarely be inherited because of an autosomal dominant mutation in one of three genes (PSEN1, PSEN2, and APP). Recognition and accurate diagnosis of these atypical forms is vital to ensure patients receive the most appropriate care and treatment.

Dynamic Occlusion and Motion Parallax in Depth Perception

Perception ◽  
1988 ◽  
Vol 17 (2) ◽  
pp. 255-266 ◽  
Author(s):  
Hiroshi Ono ◽  
Brian J Rogers ◽  
Masao Ohmi ◽  
Mika E Ono
Keyword(s):  
Relative Motion ◽  
Depth Perception ◽  
Motion Parallax ◽  
Three Dimensional ◽  
Depth Order ◽  
Depth Cues ◽  
Small Depth ◽  
Stationary Observer ◽  
Depth Separation ◽  
Condition B

Random-dot techniques were used to examine the interactions between the depth cues of dynamic occlusion and motion parallax in the perception of three-dimensional (3-D) structures, in two different situations: (a) when an observer moved laterally with respect to a rigid 3-D structure, and (b) when surfaces at different distances moved with respect to a stationary observer. In condition (a), the extent of accretion/deletion (dynamic occlusion) and the amount of relative motion (motion parallax) were both linked to the motion of the observer. When the two cues specified opposite, and therefore contradictory, depth orders, the perceived order in depth of the simulated surfaces was dependent on the magnitude of the depth separation. For small depth separations, motion parallax determined the perceived order, whereas for large separations it was determined by dynamic occlusion. In condition (b), where the motion parallax cues for depth order were inherently ambiguous, depth order was determined principally by the unambiguous occlusion information.

Balint's Syndrome in Alzheimer's Disease: Visuospatial Functions

1990 ◽  
Vol 54 (3-4) ◽  
pp. 339-346 ◽  
Author(s):  
Mario F. Mendez ◽  
Judy Turner ◽  
Grover C. Gilmore ◽  
Bernd Remler ◽  
Robert L. Tomsak
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Visuospatial Functions

Effects of Time Delay on Depth Perception via Head-Motion Parallax in Virtual Environment Systems

2000 ◽  
Vol 9 (6) ◽  
pp. 638-647 ◽  
Author(s):  
Hanfeng Yuan ◽  
W. L. Sachtler ◽  
Nat Durlach ◽  
Barbara Shinn-Cunningham
Keyword(s):  
Time Delay ◽  
Virtual Environment ◽  
Depth Perception ◽  
Head Movement ◽  
Time Delays ◽  
Motion Parallax ◽  
Head Motion ◽  
Depth Cues ◽  
Random Dot Patterns

Experiments were conducted to determine how the ability to detect and discriminate head-motion parallax depth cues is degraded by time delays between head movement and image update. The stimuli consisted of random-dot patterns that were programmed to appear as one cycle of a sinusoi dal grating when the subject's head moved. The results show that time delay between head movement and image update has essentially no effect on the ability to discrimi nate between two such gratings with different depth char acteristics when the delay is less than or equal to roughly 265 ms.

The myth of visual depth cues V: Motion parallax

2021 ◽  
Author(s):  
Lydia Maniatis
Keyword(s):  
Depth Perception ◽  
Motion Parallax ◽  
Convincing Evidence ◽  
The Other ◽  
Visual Depth ◽  
Independent Factor ◽  
Depth Cues ◽  
Depth Cue

Motion parallax is conventionally described as a “depth cue.” Rogers &amp; Graham (1979) are credited with providing fairly convincing evidence for this view. Here, I argue that, just as in the case of the other so-called “depth cues,” the claim that “motion parallax” constitutes an independent factor supporting shape and depth perception is circular. Authors offering apparent demonstrations of this cue fail to properly distinguish between proximal and distal stimulus and overlook the fundamental confound of figural organization.

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