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William John Harrison, Jason B Mattingley, Gail A Robinson; Contextual visual processing and visual working memory deficits in Alzheimer’s disease. Invest. Ophthalmol. Vis. Sci. 2019;60(9):5920.
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© ARVO (1962-2015); The Authors (2016-present)
The causes of visual dysfunction common in individuals with Alzheimer’s disease are debated. Recent work suggests that certain failures in visual identification may be attributed to cortical interactions between spatially nearby visual features, particularly for patients with posterior cortical atrophy. To date, however, such studies have only tested interactions between alphanumeric symbols. Here we use a novel method to test whether Alzheimer’s patients’ perception and visual working memory are affected when a visual target is surrounded by complex natural image context.
The patient group met criteria for probable Alzheimer’s disease (amnestic/ non-amnestic) based on clinical neurological and neuropsychological assessment. Age-matched neuro-typical observers of both sexes served as a control group. An observer’s goal was to report the orientation of a randomly oriented target sine-wave grating by rotating a probe stimulus using a digital dial. In the “matching task”, the target and probe were presented 10° above and below the screen center, respectively, and the target remained visible until a response was made. In the “memory task”, the target was presented at the screen center for one second, followed by a one second blank interval, after which the response probe appeared. In both tasks, targets were presented either on a blank background (“no context”), or within a randomly selected grayscale natural image (“natural context”).
The precision of responses (ie. the inverse of the standard deviation) was higher for control observers than patients, regardless of task. Collapsed across context condition, patients and controls both exhibited an approximate two-fold decrease in precision for the memory task compared with the matching task. We found clear individual differences according to target context: some patients had worse precision for the matching and/or memory tasks in the natural context compared with the no context condition, whereas others were unaffected by context.
We developed a simple task that is sensitive to perceptual and working memory demands. Our findings reveal that naturalistic contexts influence Alzheimer’s patients’ processing of visual orientation idiosyncratically. We plan to investigate whether these individual differences may be related to differences in disease progression and distribution of pathology.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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