Search results for "Visual field"

A Multi-Scale Colour and Keypoint Density-Based Approach for Visual Saliency Detection

2020

In the first seconds of observation of an image, several visual attention processes are involved in the identification of the visual targets that pop-out from the scene to our eyes. Saliency is the quality that makes certain regions of an image stand out from the visual field and grab our attention. Saliency detection models, inspired by visual cortex mechanisms, employ both colour and luminance features. Furthermore, both locations of pixels and presence of objects influence the Visual Attention processes. In this paper, we propose a new saliency method based on the combination of the distribution of interest points in the image with multiscale analysis, a centre bias module and a machine …

An overall description of retinotopic mapping in the cat's visual cortex areas 17, 18, and 19.

1985

Mathematical functions are derived which model the retinotopic mapping in the cat's visual cortical areas 17, 18, and 19. All three mappings are simple modifications of a complex power function with an exponent of 0.43. This function is decomposed so as to give an intermediate stage which is common to all three mappings and can be regarded as a model of the lateral geniculate nucleus mapping. The influence of retinotopic mapping on visual receptive fields was studied. The results show that a dependence of the receptive field properties on the position in the visual field is to be expected.

2021

AIM: To investigate short- and long-term intraocular pressure (IOP) fluctuations and further ocular and demographic parameters as predictors for normal tension glaucoma (NTG) progression. METHODS: This retrospective, longitudinal cohort study included 137 eyes of 75 patients with NTG, defined by glaucomatous optic disc or visual field defect with normal IOP (<21 mm Hg), independently from therapy regimen. IOP fluctuation, mean, and maximum were inspected with a mean follow-up of 38mo [standard deviation (SD) 18mo]. Inclusion criteria were the performance of minimum two 48-hour profiles including perimetry, Heidelberg retina tomograph (HRT) imaging, and optic disc photographs. The impact …

RELATIVISTIC COMPRESSION AND EXPANSION OF EXPERIENTIAL TIME IN THE LEFT AND RIGHT SPACE

2007

Time, space and numbers are closely linked in the physical world. However, the relativistic-like effects on time perception of spatial and magnitude factors remain poorly investigated. Here we wanted to investigate whether duration judgments of digit visual stimuli are biased depending on the side of space where the stimuli are presented and on the magnitude of the stimulus itself. Different groups of healthy subjects performed duration judgment tasks on various types of visual stimuli. In the first two experiments visual stimuli were constituted by digit pairs (1 and 9), presented in the centre of the screen or in the right and left space. In a third experiment visual stimuli were constitu…

Transposed-letter and laterality effects in lexical decision.

2006

Two divided visual field lexical decision experiments were conducted to examine the role of the cerebral hemispheres in transposed-letter similarity effects. In Experiment 1, we created two types of nonwords: nonadjacent transposed-letter nonwords (TRADEGIA; the base word was TRAGEDIA, the Spanish for TRAGEDY) and two-letter different nonwords (orthographic controls: TRATEPIA). In Experiment 2, the controls were one-letter different nonwords (TRAGEPIA) instead of two-letter different nonwords (TRATEPIA). The effect of transposed-letter similarity was substantially greater in the right visual field (left hemisphere) than in the left visual field. Furthermore, nonwords created by transposing …

Reliability and Intersession Agreement of Microperimetric and Fixation Measurements Obtained with a New Microperimeter in Normal Eyes.

2015

Purpose: To evaluate the reliability and intersession agreement of measurements of retinal sensitivity as well as of the fixation pattern obtained in healthy eyes with a microperimeter integrating the mechanism of the scanning laser ophthalmoscope (SLO) with the static perimetry. Methods: This study included a sample of 44 healthy eyes of 44 subjects of a mean age of 27.0 ± 8.5 years. In all cases, microperimetric exams with the MAIA system (Centervue, Padova, Italy) were performed in three different sessions to evaluate the intersession repeatability. The consistency of measurements was analyzed by using the Friedman test and by analyzing the correlation between consecutive measurements. A…

Normal Values for Microperimetry with the MAIA Microperimeter: Sensitivity and Fixation Analysis in Healthy Adults and Children

2017

Purpose To establish normative values of retinal sensitivity and parameters describing the fixation pattern using macular analyzer integrity assessment (MAIA) microperimetry (Centervue, Padova, Italy) in adults and children. Methods A sample of 237 eyes of 237 healthy subjects aged between 10 and 70 years (mean age 30.63 ± 16.23 years) was evaluated using the MAIA microperimeter. The following parameters provided by the MAIA device were evaluated: average threshold (AT), macular integrity, fixation indexes (P1% and P2%), bivariate contour ellipse area (BCEA) for 95% and 63% of points, and horizontal (H) and vertical (V) axes of the ellipse of fixation. Differences between different age-rela…

[Postural balance following stroke: towards a disadvantage of the right brain-damaged hemisphere].

1999

International audience; In the light of studies published in the last ten years, we have suspected a differential influence of the sides of hemispheric cerebral lesions on posture and balance. A study was aimed at verifying this hypothesis, the method of which being original because many possible confounding factors such as age, sex as well as topography and size of the brain lesion have been taken into account in the statistical analysis. Inclusion criteria were: right-handed patients, first stroke, no previous disease which might have affected balance. Their postural abilities (ranging from 0 to 36) were assessed 90 +/- 3 days after stroke onset on a clinical scale. This clinical assessme…

Effects of age and soccer expertise on general tests of perceptual and motor performance among adolescent soccer players.

2010

This study of perceptual and motor skills in soccer players was conducted on adolescent males. The goals were to monitor the development of general perceptual motor skills in nonsoccer-playing and soccer-playing groups ( n = 245), to examine the relationship between physical maturity and general perceptual motor skills ( n = 41), and to compare the differences in general perceptual motor skills between groups with different soccer expertise ( n = 142). The measured variables were simple reaction time, peripheral awareness, eye–hand–foot coordination, and testosterone blood level. The results suggested that general perceptual motor skills improved with age, the development of these skills w…

Multisensory integration in hemianopia and unilateral spatial neglect: Evidence from the sound induced flash illusion.

2016

Recent neuropsychological evidence suggests that acquired brain lesions can, in some instances, abolish the ability to integrate inputs from different sensory modalities, disrupting multisensory perception. We explored the ability to perceive multisensory events, in particular the integrity of audio-visual processing in the temporal domain, in brain-damaged patients with visual field defects (VFD), or with unilateral spatial neglect (USN), by assessing their sensitivity to the 'Sound-Induced Flash Illusion' (SIFI). The study yielded two key findings. Firstly, the 'fission' illusion (namely, seeing multiple flashes when a single flash is paired with multiple sounds) is reduced in both left- …