Visual cortex in aging and Alzheimer's disease: changes in visual field maps and population receptive fields

Brewer, Alyssa A.; Barton, Brian

doi:10.3389/fpsyg.2014.00074

Cited by 92 publications

(128 citation statements)

References 85 publications

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“…What follows are two multivariate ANOVA comparisons (central and peripheral eccentricities) between photopic and scotopic conditions per measurement type (coherence, preferred eccentricity, and pRF size) (23). Data from the central eccentricities of each map were used to evaluate the effects of the rod scotoma on the neural activity within the SPZ, whereas data from the more peripheral eccentricities were used to evaluate differences between cone and rod inputs.…”

Section: Resultsmentioning

confidence: 99%

fMRI of the rod scotoma elucidates cortical rod pathways and implications for lesion measurements

Barton

Brewer

2015

Proc. Natl. Acad. Sci. U.S.A.

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Are silencing, ectopic shifts, and receptive field (RF) scaling in cortical scotoma projection zones (SPZs) the result of long-term reorganization (plasticity) or short-term adaptation? Electrophysiological studies of SPZs after retinal lesions in animal models remain controversial, because they are unable to conclusively answer this question because of limitations of the methodology. Here, we used functional MRI (fMRI) visual field mapping through population RF (pRF) modeling with moving bar stimuli under photopic and scotopic conditions to measure the effects of the rod scotoma in human early visual cortex. As a naturally occurring central scotoma, it has a large cortical representation, is free of traumatic lesion complications, is completely reversible, and has not reorganized under normal conditions (but can as seen in rod monochromats). We found that the pRFs overlapping the SPZ in V1, V2, V3, hV4, and VO-1 generally (i) reduced their blood oxygen level-dependent signal coherence and (ii) shifted their pRFs more eccentric but (iii) scaled their pRF sizes in variable ways. Thus, silencing, ectopic shifts, and pRF scaling in SPZs are not unique identifiers of cortical reorganization; rather, they can be the expected result of short-term adaptation. However, are there differences between rod and cone signals in V1, V2, V3, hV4, and VO-1? We did not find differences for all five maps in more peripheral eccentricities outside of rod scotoma influence in coherence, eccentricity representation, or pRF size. Thus, rod and cone signals seem to be processed similarly in cortex. can adult human visual cortex reorganize after the removal of visual input?" This question can be studied through the effects of retinal lesions (causing scotomas), in which input from the retina has been removed, but cortical representations of the scotoma projection zone (SPZ) remain intact. Accordingly, emphasis must be placed on teasing apart effects of scotomas that relate to short-term cortical adaptation from those of long-term cortical plasticity (1) (terminology review is in ref.2). Here, we investigate this question in human cortex by using functional MRI (fMRI) to measure the immediate cortical SPZ responses in the unique paradigm of the naturally occurring rod scotoma.The photoreceptors in humans can be divided into two classes: cones, which are primarily responsible for vision under high-luminance (photopic) conditions, and rods, which are primarily responsible for vision under low-luminance (scotopic) conditions when the cones are inactive. The cones are an order of magnitude more highly concentrated in the fovea relative to the periphery, where they inform our most detailed visual experience (3). In contrast, the greatest concentrations of rods are more than ∼10°e ccentric from fixation and become increasingly sparse toward fixation until they are completely absent. This roughly circular rodfree zone covers a radius of ∼0.6-0.8°of visual angle about the fixation point (diameter = ∼1.25-1.7°) (4, 5). Under scotopic conditions, a...

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Section: Resultsmentioning

confidence: 99%

fMRI of the rod scotoma elucidates cortical rod pathways and implications for lesion measurements

Barton

Brewer

2015

Proc. Natl. Acad. Sci. U.S.A.

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“…To date, there is a small literature developing in elderly subjects [63, 81, 82] but no population receptive field studies in children. Characterization of maps and pRF properties in development and normal aging will provide useful benchmarks for clinical and scientific questions.…”

Section: Figurementioning

confidence: 99%

Computational neuroimaging and population receptive fields

Wandell

Winawer

2015

Trends in Cognitive Sciences

229

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Functional magnetic resonance imaging (fMRI) noninvasively measures human brain activity at millimeter resolution. Scientists use very different approaches to take advantage of the remarkable opportunities presented by fMRI. We describe progress using the computational neuroimaging approach in human visual cortex, which aims to build models that predict the neural responses from the stimulus and task. We focus on a particularly active area of research, the use of population receptive field (pRF) models to characterize human visual cortex responses to a range of stimuli, in a variety of tasks, and in different subject populations.

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“…212 The transition between normal ageing, MCI, and AD is often indistinct but pathological changes suggest early changes in medial temporal lobe spreading to affect neocortical regions 213 while brain imaging studies often suggest early changes in the posterior/temporal parietal region and in occipital cortex with NFT affecting B19 (V3). 214 These observations support the hypothesis that retinal pathology in AD may result from retrograde degeneration from association areas reducing axonal input to the eye.…”

Section: Visual Cortexmentioning

confidence: 99%

Oculo‐visual changes and clinical considerations affecting older patients with dementia

Armstrong

Kergoat

2015

Ophthalmic Physiologic Optic

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Purpose Dementia is associated with various alterations of the eye and visual function. Over 60% of cases are attributable to Alzheimer's disease, a significant proportion of the remainder to vascular dementia or dementia with Lewy bodies, while frontotemporal dementia, and Parkinson's disease dementia are less common. This review describes the oculo‐visual problems of these five dementias and the pathological changes which may explain these symptoms. It further discusses clinical considerations to help the clinician care for older patients affected by dementia. Recent findings Visual problems in dementia include loss of visual acuity, defects in colour vision and visual masking tests, changes in pupillary response to mydriatics, defects in fixation and smooth and saccadic eye movements, changes in contrast sensitivity function and visual evoked potentials, and disturbance of complex visual functions such as in reading ability, visuospatial function, and the naming and identification of objects. Pathological changes have also been reported affecting the crystalline lens, retina, optic nerve, and visual cortex. Clinically, issues such as cataract surgery, correcting the refractive error, quality of life, falls, visual impairment and eye care for dementia have been addressed. Summary Many visual changes occur across dementias, are controversial, often based on limited patient numbers, and no single feature can be regarded as diagnostic of any specific dementia. Nevertheless, visual hallucinations may be more characteristic of dementia with Lewy bodies and Parkinson's disease dementia than Alzheimer's disease or frontotemporal dementia. Differences in saccadic eye movement dysfunction may also help to distinguish Alzheimer's disease from frontotemporal dementia and Parkinson's disease dementia from dementia with Lewy bodies. Eye care professionals need to keep informed of the growing literature in vision/dementia, be attentive to signs and symptoms suggestive of cognitive impairment, and be able to adapt their practice and clinical interventions to best serve patients with dementia.

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Visual cortex in aging and Alzheimer's disease: changes in visual field maps and population receptive fields

Cited by 92 publications

References 85 publications

fMRI of the rod scotoma elucidates cortical rod pathways and implications for lesion measurements

fMRI of the rod scotoma elucidates cortical rod pathways and implications for lesion measurements

Computational neuroimaging and population receptive fields

Oculo‐visual changes and clinical considerations affecting older patients with dementia

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