Search results for "Psychophysics"

Color stimuli perception in presence of light scattering.

2006

Perception of different color contrast stimuli was studied in the presence of light scattering: in a fog chamber in Clermont-Ferrand and in laboratory conditions where light scattering of similar levels was obtained, using different light scattering eye occluders. Blue (shortest wavelength) light is scattered in fog to the greatest extent, causing deterioration of vision quality especially for the monochromatic blue stimuli. However, for the color stimuli presented on a white background, visual acuity in fog for blue Landolt-C optotypes was higher than for red and green optotypes on the white background. The luminance of color Landolt-C optotypes presented on a LCD screen was chosen corresp…

100 Years of Benham's Top in Colour Science

1995

For 100 years Benham's top has been a popular device demonstrating pattern-induced flicker colours (PIFCs). Results of early and recent investigations on PIFCs are reported and show that the phenomenon originates in phase-sensitive lateral interactions of modulated neural activity in the retina followed by additional spatial interactions in the visual cortex behind the locus of binocular fusion. Colour matches with normal colour stimuli indicate that S/(M + L) opponent neurons are involved. Dichromats do not find matching stimuli for all PIFCs. PIFCs may become useful in medical diagnosis. The phenomenon is interpreted as a side effect of a neural mechanism providing colour constancy under…

Spatio-temporal Contrast Sensitivity in the Cardinal Directions of the Colour Space. A Review

2010

AbstractWe review the psychophysics of the spatio-temporal contrast sensitivity in the cardinal directions of the colour space and their correlation with those neural characteristics of the visual system that limit the ability to perform contrast detection or pattern-resolution tasks. We focus our attention particularly on the influence of luminance level, spatial extent and spatial location of the stimuli - factors that determine the characteristics of the physiological mechanisms underlying detection. Optical factors do obviously play a role, but we will refer to them only briefly. Contrast sensitivity measurements are often used in clinical practice as a method to detect, at their early …

Parallel Adaptation to Spatially Distinct Distortions

2020

Optical distortions as a visual disturbance are inherent in many optical devices such as spectacles or virtual reality headsets. In such devices, distortions vary spatially across the visual field. In progressive addition lenses, for example, the left and right regions of the lens skew the peripheral parts of the wearers visual field in opposing directions. The human visual system adapts to homogeneous distortions and the respective aftereffects are transferred to non-retinotopic locations. This study investigates simultaneous adaptation to two opposing distortions at different retinotopic locations. Two oppositely skewed natural image sequences were presented to 10 subjects as adaptation s…

Speech technology as an experimental science: towards the comparative dynamics of Sprechkunde in Germany and Russia in the late nineteenth to early t…

2016

The article examines various resonances of the “speech technology” (Sprechkunde) current in German and Russian-Soviet context of 1900–1920s. It contains first of all a brief history of the techniques of speech in Germany, an inquiry into some psychophysical sources of the “speech technology” and a survey of the contribution of German “new rhetoric” to this movement. The Russian counterparts of this trend include the Institute of the Living Word (Institut živogo slova, 1918–1923), some Russian formalists, the scenic speech specialists and the theatre pedagogues. The conclusion summarises the historical significance of “speech technology” and its common features in Germany and Russia. It turn…

Psychophysical and electrofunctional contrast sensitivity in cataractous patients treated with bendazac-lysine salt

1990

The clinical progression of the cataract may be influenced by drugs which reduce the denaturation of lens proteins. One of the most promising drugs is the bendazac-lysine salt. The drug was used in a double-blind study of a group of patients with initial cortical cataract in order to evaluate the changes in visual acuity and contrast sensitivity by means of a psychophysical and an electrophysiological method. After 6 months of treatment with bendazac the mean values of visual acuity showed a statistically significant increase in respect to baseline values, as well as an improvement of the threshold of contrast for most spatial frequencies. In the eyes treated with placebo there was no stati…

2014

Nonsimultaneous maskers can strongly impair performance in an auditory intensity discrimination task. Using methods of molecular psychophysics, we quantified the extent to which (1) a masker-induced impairment of the representation of target intensity (i.e., increase in internal noise) and (2) a systematic influence of the masker intensities on the decision variable contribute to these effects. In a two-interval intensity discrimination procedure, targets were presented in quiet, and combined with forward maskers. The lateralization of the maskers relative to the targets was varied via the interaural time difference. Intensity difference limens (DLs) were strongly elevated under forward mas…

S2.2 Assessment of neuropathic pain. I. Psychophysical methods

2006

Color-discrimination threshold determination using pseudoisochromatic test plates

2014

We produced a set of pseudoisochromatic plates for determining individual color-difference thresholds to assess test performance and test properties, and analyzed the results. We report a high test validity and classification ability for the deficiency type and severity level [comparable to that of the fourth edition of the Hardy–Rand–Rittler (HRR) test]. We discuss changes of the acceptable chromatic shifts from the protan and deutan confusion lines along the CIE xy diagram, and the high correlation of individual color-difference thresholds and the red–green discrimination index. Color vision was tested using an Oculus HMC anomaloscope, a Farnsworth D15, and an HRR test on 273 schoolchildr…

PARI 2010-2011 - Projet DINOS "Innovinaroma" ou Mélanges d'odorants et milieux complexes

2011

L'idée est de réaliser une méta-analyse non ciblée de données d'origines multiples afin de prendre en compte à la fois les résultats de l'analyse sensorielle établie sur le concept de typicité mais aussi celles de l'olfactométrie séparative, de l'analyse semi-quantitative, de la chimie des odorants identifiés, de la psychophysique et de l'aromatique alimentaire. Le statut de composés clés porteurs de typicité aromatique, relève de leur présence en mélange dans des gammes de concentrations et dans un environnement à la fois complexe et diversifié propre à la catégorie sensorielle cible. Les approches, dont le but était de faire émerger un tel groupe d'odorants, jusqu'ici trop simplistes ou t…