When adjusting the contrast setting on a television set, we experience a perceptual change in the global image contrast. But how is that statistic computed? We addressed this using a contrast-matching task for checkerboard configurations of micro-patterns in which the contrasts and spatial spreads of two interdigitated components were controlled independently. When the patterns differed greatly...

Previous contrast discrimination experiments have shown that luminance contrast is summed across ocular (T. S. Meese, M. A. Georgeson, & D. H. Baker, 2006) and spatial (T. S. Meese & R. J. Summers, 2007) dimensions at threshold and above. However, is this process sufficiently general to operate across the conjunction of eyes and space? Here we used a "Swiss cheese" stimulus where the blurred "h...

A sum graph G is a graph with a mapping of the vertex set of G onto a set of positive integers S in such a way that two vertices of G are adjacent if and only if the sum of their labels is an element of S. In an exclusive sum graph the integers of S that are the sum of two other integers of S form a set of integers that label a collection of isolated vertices associated with the graph G. A grap...

When adjusting the contrast setting on a television set, we experience a perceptual change in the global image contrast. But how is that statistic computed? We addressed this using a contrast-matching task for checkerboard configurations of micro-patterns in which the contrasts and spatial spreads of two interdigitated components were controlled independently. When the patterns differed greatly...

1. Human visual selectivity for direction of movement was determined using a subthreshold summation technique. 2. The threshold contrast for detecting a drifting sinusoidal grating was found to be independent of the contrast of an added subthreshold grating which moved in the opposite direction. 3. The detection threshold for a counterphase flickering grating is twice that for a moving grating,...

1. Variation in stimulus contrast produces a marked effect on the dynamics of the cat retina. This contrast effect was investigated by measurement of the responses of X and Y ganglion cells. The stimuli were sine gratings or rectangular spots modulated by a temporal signal which was a sum of sinusoids. Fourier analysis of the neural response to such a stimulus allowed us to calculate first orde...

introduction: during the angiography of coronary vessels a great amount of  iodine mixed with radio-contrasts enter the body, and if autonomic centers exist in thyroid it causes hyperthyroidism. this can be dangerous in patients with cronary artery disease (cad). this study aimed to determine the effect of a radio-contrast used in coronary angiohraphy on thyroid’s function in patients referring...

abstract background and aim: consider ing based on the presence or absence of swelling of the optic disc, optic neuritis classified nto two types of anterior and retrobulbar optic neuritis. the aim of this study was to compare the visual functions of patients with anterior optic neuritis and retrobulbar optic neuritis. materials and methods:this cross-sectional study was conducted in 48 patient...

let g be a (p,q) graph. an injective map f : e(g) → {±1,±2,...,±q} is said to be an edge pair sum labeling if the induced vertex function f*: v (g) → z - {0} defi ned by f*(v) = σp∈ev f (e) is one-one where ev denotes the set of edges in g that are incident with a vertex v and f*(v (g)) is either of the form {±k1,±k2,...,±kp/2} or {±k1,±k2,...,±k(p-1)/2} u {±k(p+1)/2} according a...

Editorial Staff Assistant Managing Editor: Dawn Bennett Senior Editors: Eleanore Butz, R. Brooks Hanson, Barbara Jasny, Katrina L. Kelner, David Lindley, Linda J. Miller, Phillip D. Szuromi, David F. Voss Associate Editors: GilbertJ. Chin, PamelaJ. Hines, Paula A. Kiberstis, Suki Parks, L. Bryan Ray Letters: Christine Gilbert, Editor; Steven S. Lapham Book Reviews: Katherine Livingston, Editor;...