scholarly journals Role of the Dorsal Posterior Parietal Cortex in the Accurate Perception of Object Magnitude in Peripheral Vision

i-Perception ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 204166952110584
Author(s):  
Tristan Jurkiewicz ◽  
Romeo Salemme ◽  
Caroline Froment ◽  
Laure Pisella
Keyword(s):  
Visual Field ◽  
Posterior Parietal Cortex ◽  
Peripheral Vision ◽  
Visual Fields ◽  
Size Perception ◽  
Control Group ◽  
Optic Ataxia ◽  
Actual Object ◽  
Pointing Errors ◽  
Accurate Perception

Following superior parietal lobule and intraparietal sulcus (SPL-IPS) damage, optic ataxia patients underestimate the distance of objects in the ataxic visual field such that they produce hypometric pointing errors. The metrics of these pointing errors relative to visual target eccentricity fit the cortical magnification of central vision. The SPL-IPS would therefore implement an active “peripheral magnification” to match the real metrics of the environment for accurate action. We further hypothesized that this active compensation of the central magnification by the SPL-IPS contributes to actual object’ size perception in peripheral vision. Three optic ataxia patients and 10 age-matched controls were assessed in comparing the thickness of two rectangles flashed simultaneously, one in central and another in peripheral vision. The bilateral optic ataxia patient exhibited exaggerated underestimation bias and uncertainty compared to the control group in both visual fields. The two unilateral optic ataxia patients exhibited a pathological asymmetry between visual fields: size perception performance was affected in their contralesional peripheral visual field compared to their healthy side. These results demonstrate that the SPL-IPS contributes to accurate size perception in peripheral vision.

scholarly journals Visually guided reaching in Alzheimer's disease and mild cognitive impairment

2020 ◽  
Author(s):  
Alexandra Grace Mitchell ◽  
Stephanie Rossit ◽  
Suvankar Pal ◽  
Michael Hornberger ◽  
Annie Warman ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Cognitive Impairment ◽  
Mild Cognitive Impairment ◽  
Posterior Parietal Cortex ◽  
Peripheral Vision ◽  
Control Group ◽  
Optic Ataxia ◽  
Individual Level ◽  
Radial Depth

Recent evidence has implicated areas within the posterior parietal cortex (PPC), as among the first to show pathophysiological changes in Alzheimer’s disease. Focal brain damage to the PPC can cause optic ataxia, a specific deficit in reaching to peripheral targets. Visuomotor deficits in optic ataxia are often only detected when reaching to objects in peripheral vision, therefore this condition can often go unnoticed. The present study investigated whether peripheral misreaching is a feature of Alzheimer’s disease. Reaching ability was assessed in individuals with a clinical diagnosis of mild-to-moderate Alzheimer’s and mild cognitive impairment (MCI), compared to a control group of healthy, older adults. Participants were required to reach to targets presented in central vision or in the periphery using two reaching tasks; one in the lateral plane and another presented in radial depth. Case-control comparisons identified 1/10 MCI and 3/17 Alzheimer’s patients with severe peripheral reaching deficits at the individual level, but group-level comparisons did not find significantly higher peripheral reaching error in neither Alzheimer’s nor MCI groups. However, exploratory analyses showed significantly increased reach duration in both Alzheimer’s and MCI groups relative to controls. We conclude that Alzheimer’s disease may lead to a visuomotor impairment that is compensated for by a slowing down of the reach movement to maintain accuracy. However, these findings suggest that peripheral reaching deficits similar to what is observed in optic ataxia are unlikely to be a common feature of Alzheimer’s disease.

Effect of Practice on Expansion of Peripheral Vision

1973 ◽  
Vol 37 (3) ◽  
pp. 720-722 ◽  
Author(s):  
A. Louise Sailor
Keyword(s):  
Visual Field ◽  
Analysis Of Variance ◽  
Stimulus Object ◽  
Peripheral Vision ◽  
Visual Fields ◽  
Speed Reading ◽  
And Control ◽  
Experimental Partner

This study was designed to test the effect of practice on the expansion of peripheral vision. 24 college speed reading students were tested for a measure of peripheral vision with a Lafayette Color Perimeter. Half of the Ss practiced detection of a white stimulus object for a period of 6 wk. Ss serving as controls assisted by moving the carrier into the visual field of an experimental partner. Analysis of variance showed significant increase in visual fields for all Ss, experimental and control. Attention factors and equipment used in the speed reading classes appear to account for these results.

Practice Effects on Reaction Time for Peripheral and Central Visual Fields

2002 ◽  
Vol 95 (3) ◽  
pp. 747-751 ◽  
Author(s):  
Soichi Ando ◽  
Noriyuki Kida ◽  
Shingo Oda
Keyword(s):  
Visual Field ◽  
Processing Time ◽  
Peripheral Vision ◽  
Visual Fields ◽  
Male Students ◽  
Practice Effects ◽  
Central Vision ◽  
Central Visual Field ◽  
Key Press ◽  
Before And After

The present study examined whether EMG-RT (KT) for a key press to stimulus in peripheral and central visual fields decreases with practice. 16 male students were divided into two groups, one practicing using peripheral vision, the other practicing using central vision. Before and after practice, RT was measured for peripheral and central visual fields. Each group practiced three blocks of 25 trials five days a week for three weeks. RT for peripheral and central visual fields decreased with practice. Practice effects on RT for the peripheral visual field extended to RT for the central visual field, and vice versa. It is suggested that the transfer may reflect the decrease in the central nervous system's processing time in common between two RT tasks.

The Effect of a Central Task on Luminance Thresholds for Peripherally Presented Stimuli

1969 ◽  
Vol 11 (4) ◽  
pp. 387-391 ◽  
Author(s):  
H. W. Leibowitz ◽  
Stuart Appelle
Keyword(s):  
Visual Field ◽  
Peripheral Vision ◽  
Control Group ◽  
Threshold Values ◽  
Fixation Light ◽  
Central Task ◽  
Steady Fixation ◽  
Luminance Threshold ◽  
The Subject

The effect of a central task on peripheral vision was investigated by obtaining luminance thresholds for stimuli presented from 20° to 90° in the periphery. A control group observed a steady foveal fixation light. For the two experimental groups, the fixation light was interrupted periodically and the subject was required to maintain illumination of the light by pressing a button. Interruption rates of 15 and 53 times per minute were investigated. The control condition with the steady fixation light produced the lowest thresholds. For the interrupted conditions, thresholds were higher for the near periphery but differences disappeared in the far periphery. Luminance threshold values were generally highest for the 15-per-minute interrupted group. The results are interpreted as reflecting the effect of an attention-demanding central task on the size of the functional visual field.

scholarly journals Optic Chiasm Width in Normal-Tension and High-Tension Glaucoma

2020 ◽  
Vol 76 (3) ◽  
pp. 126-128
Author(s):  
Ján Lešták ◽  
Martin Kynčl ◽  
Martin Fůs ◽  
Klára Marešová
Keyword(s):  
Visual Field ◽  
Visual Fields ◽  
Optic Chiasm ◽  
Control Group ◽  
Ophthalmological Examination ◽  
Field Of Vision ◽  
High Tension ◽  
Significant Difference ◽  
Electrophysiological Examination ◽  
Corpus Geniculatum Laterale

Purpose: The aim of our study was to find out whether in patients with hypertensive glaucoma (HTG) and normotensive glaucoma (NTG), there is a change in the size of the chiasm depending on the changes in the visual field. Therefore, we retrospectively measured the width of the chiasm in the patients to whom we measured the size of the corpus geniculatum laterale in 2013. Materials and methods: The group consisted of two groups of patients. Nine with hypertensive glaucoma (HTG) and nine with normotensive glaucoma (NTG). The diagnosis was based on a complex ophthalmological examination and in NTG and electrophysiological examination. The visual field was examined by a rapid threshold program on the Medmont M700. The sum of the sensitivity from both visual fields in the range of 0-22 degrees was compared with the width of the chiasm obtained by the magnetic resonance imaging using the eight channel head coil. The measured values of all subjects were analyzed using a paired t-test and a correlation coefficient. Results: We found a reduction in the chiasma width in both glaucoma groups. We found a statistically significant difference in the size of the chiasm (p = 0.0003) between the control group and the HTG group (p = 0.001). The narrowing of the chiasm showed a slight correlation in HTG with changes in the field of vision (r = 0.139) and in NTG a moderate correlation (r = 0.375). Conclusion: We found a reduction in the size of the chiasm in both HTG and NTG. The sum of sensitivities in the central parts of the visual field, however, more correlated with the reduction in the size of the chiasm in NTG. This finding shows that there are two different diagnostic groups.

Visual Field Accuracy and Eye Movement Direction: A Child's Eye View

1980 ◽  
Vol 50 (2) ◽  
pp. 631-636
Author(s):  
Evans Mandes
Keyword(s):  
Eye Movements ◽  
Visual Field ◽  
Eye Movement ◽  
Visual Fields ◽  
Movement Direction

Post-exposural eye movements were studied in 32 adults and 24 7-yr.-old children. Stimuli were binary figures exposed tachistoscopically in both visual fields simultaneously. The data showed significant correlations between direction of eye movement and locus of recognition for both children and adults. No significant differences were found in frequencies of eye movements of children and adults. The data are interpreted in terms of the facilitative effects of post-exposural eye movements upon perception for both groups.

scholarly journals What do patients with glaucoma see: a novel iPad app to improve glaucoma patient awareness of visual field loss

2020 ◽  
pp. bjophthalmol-2020-317034
Author(s):  
Meghal Gagrani ◽  
Jideofor Ndulue ◽  
David Anderson ◽  
Sachin Kedar ◽  
Vikas Gulati ◽  
...  
Keyword(s):  
Visual Field ◽  
Vision Loss ◽  
Peripheral Vision ◽  
Glaucoma Patient ◽  
Visual Field Loss ◽  
Sensitivity Threshold ◽  
Roc Curve Analysis ◽  
The Mean ◽  
Ipad App ◽  
Field Defects

PurposeGlaucoma patients with peripheral vision loss have in the past subjectively described their field loss as ‘blurred’ or ‘no vision compromise’. We developed an iPad app for patients to self-characterise perception within areas of glaucomatous visual field loss.MethodsTwelve glaucoma patients with visual acuity ≥20/40 in each eye, stable and reliable Humphrey Visual Field (HVF) over 2 years were enrolled. An iPad app (held at 33 cm) allowed subjects to modify ‘blur’ or ‘dimness’ to match their perception of a 2×2 m wall-mounted poster at 1 m distance. Subjects fixated at the centre of the poster (spanning 45° of field from centre). The output was degree of blur/dim: normal, mild and severe noted on the iPad image at the 54 retinal loci tested by the HVF 24-2 and was compared to threshold sensitivity values at these loci. Monocular (Right eye (OD), left eye (OS)) HVF responses were used to calculate an integrated binocular (OU) visual field index (VFI). All three data sets were analysed separately.Results36 HVF and iPad responses from 12 subjects (mean age 71±8.2y) were analysed. The mean VFI was 77% OD, 76% OS, 83% OU. The most common iPad response reported was normal followed by blur. No subject reported dim response. The mean HVF sensitivity threshold was significantly associated with the iPad response at the corresponding retinal loci (For OD, OS and OU, respectively (dB): normal: 23, 25, 27; mild blur: 18, 16, 22; severe blur: 9, 9, 11). On receiver operative characteristic (ROC) curve analysis, the HVF retinal sensitivity cut-off at which subjects reported blur was 23.4 OD, 23 OS and 23.3 OU (dB).ConclusionsGlaucoma subjects self-pictorialised their field defects as blur; never dim or black. Our innovation allows translation of HVF data to quantitatively characterise visual perception in patients with glaucomatous field defects.

scholarly journals Association of ocular blood flow and contrast sensitivity in normal tension glaucoma

2021 ◽  
Author(s):  
David Kuerten ◽  
Matthias Fuest ◽  
Peter Walter ◽  
Babac Mazinani ◽  
Niklas Plange
Keyword(s):  
Blood Flow ◽  
Visual Field ◽  
Contrast Sensitivity ◽  
Visual Field Defect ◽  
Prospective Trial ◽  
Normal Tension Glaucoma ◽  
Ocular Blood Flow ◽  
Retinal Blood Flow ◽  
Control Group ◽  
Field Defect

Abstract Purpose To investigate the relationship of ocular blood flow (via arteriovenous passage time, AVP) and contrast sensitivity (CS) in healthy as well as normal tension glaucoma (NTG) subjects. Design Mono-center comparative prospective trial Methods Twenty-five NTG patients without medication and 25 healthy test participants were recruited. AVP as a measure of retinal blood flow was recorded via fluorescein angiography after CS measurement using digital image analysis. Association of AVP and CS at 4 spatial frequencies (3, 6, 12, and 18 cycles per degree, cpd) was explored with correlation analysis. Results Significant differences regarding AVP, visual field defect, intraocular pressure, and CS measurement were recorded in-between the control group and NTG patients. In NTG patients, AVP was significantly correlated to CS at all investigated cpd (3 cpd: r =  − 0.432, p< 0.03; 6 cpd: r =  − 0.629, p< 0.0005; 12 cpd: r =  − 0.535, p< 0.005; and 18 cpd: r =  − 0.58, p< 0.001), whereas no significant correlations were found in the control group. Visual acuity was significantly correlated to CS at 6, 12, and 18 cpd in NTG patients (r =  − 0.68, p< 0.002; r =  − 0.54, p< .02, and r =  − 0.88, p< 0.0001 respectively), however not in healthy control patients. Age, visual field defect MD, and PSD were not significantly correlated to CS in in the NTG group. MD and PSD were significantly correlated to CS at 3 cpd in healthy eyes (r = 0.55, p< 0.02; r =  − 0.47, p< 0.03). Conclusion Retinal blood flow alterations show a relationship with contrast sensitivity loss in NTG patients. This might reflect a disease-related link between retinal blood flow and visual function. This association was not recorded in healthy volunteers.

scholarly journals Functional visual fields: relationship of visual field areas to self-reported function

2017 ◽  
Vol 37 (4) ◽  
pp. 399-408 ◽  
Author(s):  
Hikmat Subhi ◽  
Keziah Latham ◽  
Joy Myint ◽  
Michael D. Crossland
Keyword(s):  
Visual Field ◽  
Visual Fields ◽  
Relationship Of

scholarly journals The Role of the Parietal Lobe in Visual Extinction Studied with Transcranial Magnetic Stimulation

2009 ◽  
Vol 21 (10) ◽  
pp. 1946-1955 ◽  
Author(s):  
Lorella Battelli ◽  
George A. Alvarez ◽  
Thomas Carlson ◽  
Alvaro Pascual-Leone
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Visual Tracking ◽  
Magnetic Stimulation ◽  
Posterior Parietal Cortex ◽  
Parietal Lobe ◽  
Repetitive Transcranial Magnetic Stimulation ◽  
Visual Fields ◽  
Brain Regions ◽  
Visual Extinction ◽  
Interhemispheric Competition

Interhemispheric competition between homologous areas in the human brain is believed to be involved in a wide variety of human behaviors from motor activity to visual perception and particularly attention. For example, patients with lesions in the posterior parietal cortex are unable to selectively track objects in the contralesional side of visual space when targets are simultaneously present in the ipsilesional visual field, a form of visual extinction. Visual extinction may arise due to an imbalance in the normal interhemispheric competition. To directly assess the issue of reciprocal inhibition, we used fMRI to localize those brain regions active during attention-based visual tracking and then applied low-frequency repetitive transcranial magnetic stimulation over identified areas in the left and right intraparietal sulcus to asses the behavioral effects on visual tracking. We induced a severe impairment in visual tracking that was selective for conditions of simultaneous tracking in both visual fields. Our data show that the parietal lobe is essential for visual tracking and that the two hemispheres compete for attentional resources during tracking. Our results provide a neuronal basis for visual extinction in patients with parietal lobe damage.

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