Search results for "Psychophysic"

Multicenter investigation of 1,036 subjects using a standardized method for the assessment of olfactory function combining tests of odor identificati…

2000

“Sniffin’ Sticks” is a test of nasal chemosensory performance that is based on penlike odor-dispensing devices. It is comprised of three tests of olfactory function: tests for odor threshold, discrimination and identification. Previous work has already established its test-retest reliability and validity in comparison to established measures of olfactory sensitivity. The results of this test are presented as a composite TDI score – i.e., the sum of results obtained for threshold, discrimination and identification measures. The present multicenter investigation aimed at providing normative values in relation to different age groups. To this end, 966 patients were investigated in 11 centers. …

¿Qué pueden aportar las ciencias de la visión al diseño gráfico?

2020

[ES] El diseño gráfico es importante y necesario en el mundo de hoy porque la vista es la principal forma de adquisición de información. Por lo tanto, es lógico pensar que las ciencias de la visión pueden ayudar en la toma de decisiones a nivel de diseño. Comprender conceptos como la agudeza visual, la sensibilidad al contraste, entre otros, contribuirá a optimizar la legibilidad del texto a través de una selección óptima de parámetros tipográficos para formatos impresos y digitales. Además, entender el efecto de las diferentes alteraciones en la visión del color mejorará la accesibilidad del diseño.

Dependence of Perceived Purity of a Chromatic Stimulus on Saturation Adaptation

2012

Background and Objective. The purpose of sensory adaptation of the visual system is to adjust sensitivity of the photoreceptors to optimize the dynamic range of response of the visual system. It has been shown in numerous research papers that chromatic adaptation influences both color appearance and color discrimination. However, there are almost no studies in which the influence of chromatic adaptation on perceived purity has been investigated. Therefore, the aim of this study was to investigate how chromatic adaptation to stimuli with certain saturation influences perceived purity of test stimuli with the same hue but different saturation. Material and Methods. As the stimuli were modulat…

Botulinum Toxin A reduces neurogenic flare but has almost no effect on pain and hyperalgesia in human skin.

2003

Botulinum toxin A (BoNT/A) has been used therapeutically to treat muscular hypercontractions and sudomotor hyperactivity. There is increasing evidence that BoNT/A might also have analgesic properties, in particular in headache. In the present investigation we tested the often cited hypothesis that BoNT/A-induced analgesia can be attributed to inhibition of neuropeptide release from nociceptive nerve fibers. In 15 healthy volunteers BoNT/A (5, 10, 20 mouse units BOTOX) or saline (contralateral side) was injected intracutaneously on the volar forearm. On day zero, the day of injection, no further tests were performed. We repeatedly elicited pain, mechanical hyperalgesia and neurogenic flare b…

Luminance and contrast in visual perception of time to collision.

2013

AbstractMany animals avoid dark, approaching objects seen against a lighter background but show no or weaker reactions to stimuli with inverted contrast. We investigated whether human observers would respond differently to such stimuli in terms of estimated time-to-arrival. We varied luminances of an approaching, light or dark disk and a plain, grey background, and for several conditions, continuously adjusted calibrations so as to keep contrast and/or overall lightness constant. Since no effects were found, we conclude that humans are able to discard luminance and contrast for the task at hand. Generally, however, performance was affected by different, consecutive regimes of feedback: Init…

2013

The motion energy sensor has been shown to account for a wide range of physiological and psychophysical results in motion detection and discrimination studies. It has become established as the standard computational model for retinal movement sensing in the human visual system. Adaptation effects have been extensively studied in the psychophysical literature on motion perception, and play a crucial role in theoretical debates, but the current implementation of the energy sensor does not provide directly for modelling adaptation-induced changes in output. We describe an extension of the model to incorporate changes in output due to adaptation. The extended model first computes a space-time r…

Olfactory function in children assessed with psychophysical and electrophysiological techniques

2007

International audience; The olfactory information processing abilities of children undergo changes during early life. The aims of the present study were to describe these changes and to probe for their electrophysiological correlates. These aims were investigated in two experiments. In Experiment 1, responses of 146 subjects (3-12 years) were tested with psychophysical tools. Approximately 2/3 of the subjects completed the olfactory tests ("Sniffin' Sticks"). In Experiment 2, 12 additional subjects (3-10 years) were tested with electrophysiological tools. Event-related potentials (ERPs) were recorded in response to olfactory stimulation with H(2)S. Results from Experiment 1 indicated that d…

The pattern and time course of somatosensory changes in the human UVB sunburn model reveal the presence of peripheral and central sensitization.

2013

The ultraviolet B (UVB) sunburn model was characterized with a comprehensive battery of quantitative sensory testing (QST). Primary hyperalgesia in UVB-irradiated skin and secondary hyperalgesia in adjacent nonirradiated skin were studied in 22 healthy subjects 24h after irradiation with UVB at 3-fold minimal erythema dose of a skin area 5 cm in diameter at the thigh and compared to mirror-image contralateral control areas. The time course of hyperalgesia over 96 h was studied in a subgroup of 12 subjects. Within the sunburn area, cold hyperesthesia (P=.01), profound generalized hyperalgesia to heat (P.001), cold (P.05), pinprick and pressure (P.001), and mild dynamic mechanical allodynia (…

Psychophysics, flare, and neurosecretory function in human pain models: capsaicin versus electrically evoked pain.

2007

Intradermal capsaicin injection (CAP) and electrical current stimulation (ES) are analyzed in respect to patterns and test-retest reliability of pain as well as sensory and neurosecretory changes. In 10 healthy subjects, 2 CAP (50 g) and 2 ES (5 to 30 mA) were applied to the volar forearm. The time period between 2 identical stimulations was about 4 months. Pain ratings, areas of mechanical hyperalgesia, and allodynia were assessed. The intensity of sensory changes was quantified by using quantitative sensory testing. Neurogenic flare was assessed by using laser Doppler imaging. Calcito- nin gene-related peptide (CGRP) release was quantified by dermal microdialysis in combination with an en…

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…