Non-cardinal color mechanism elicitation by stimulus shape: Bringing the S versus L+M color plane to the table.

Neurons in the cortex typically respond best to elongated stimuli, or gratings, whereas neurons in the lateral geniculate nucleus (LGN) typically prefer circular stimuli, or spots. Further, neural mechanisms specifically tuned for non-cardinal colors largely do not emerge until the cortex; therefore, the use of gratings should better reveal non-cardinal color mechanisms. This hypothesis has been tested in the isoluminant color plane in macaque monkeys (Stoughton, Lafer-Sousa, Gagin, & Conway, 2012) and in the L-M versus L+M color plane in human subjects (Gegenfurtner & Kiper, 1992).

Poor peripheral binding depends in part on stimulus color.

We have compared two explanations for poor peripheral binding. Binding is the ability to assign the correct features (e.g.

Trombones Elicit Bitter More Strongly Than Do Clarinets: a Partial Replication of Three Studies of Crisinel and Spence.

We present a partial replication of the crossmodal pitch/taste correspondence of Crisinel and Spence. Male college students (n=46) were asked to judge the pitch (F1-C4 on trombone; F3-C6 on clarinet) that best corresponded with each of four tastants (unsweetened coffee, unsweetened chocolate, salt, and sugar). With trombone there was a significant effect of tastant [F(3,135)=7.

Influence of stimulus size on revealing non-cardinal color mechanisms.

Multiple studies have shown that performance of subjects on a number of visual tasks is worse for non-cardinal than cardinal colors, especially in the red-green/luminance (RG/LUM) and tritan/luminance (TRIT/LUM) color planes. Inspired by neurophysiological evidence that suppressive surround input to receptive fields is particularly sensitive to luminance, we hypothesized that non-cardinal mechanisms in the RG/LUM and TRIT/LUM planes would be more sensitive to stimulus size than are isoluminant non-cardinal mechanisms. In Experiment 1 we tested 9-10 color-normal subjects in each of the three color planes (RG/TRIT, RG/LUM, and TRIT/LUM) on visual search at four bull's-eye dot sizes (0.

Non-cardinal color mechanism strength differs across color planes but not across subjects.

This study tested two hypotheses: (1) that non-cardinal color mechanisms may be due to individual differences: some subjects have them (or have stronger ones), while other subjects do not; and (2) that non-cardinal mechanisms may be stronger in the isoluminant plane of color space than in the two planes with luminance. Five to six subjects per color plane were tested on three psychophysical paradigms: adaptation, noise masking, and plaid coherence. There were no consistent individual differences in non-cardinal mechanism strength across the three paradigms.

Non-cardinal color perception across the retina: easy for orange, hard for burgundy and sky blue.

Cardinal color performance (reddish, greenish, bluish, yellowish, black, and white) has been shown to decline in peripheral viewing. What about non-cardinal color performance (e.g.

A tritan Waldo would be easier to detect in the periphery than a red/green one: evidence from visual search.

In a color naming task from 0° to 55° eccentricity, we found that red/green performance (n=10 subjects) declines around 40° eccentricity, 5° earlier than does tritan performance (main effect of color, p=0.009; eccentricity, p<0.001; interaction, p=0.

The use of "non-fiction novels" in a sensation and perception course.

Scientific material can be difficult to relate to everyday knowledge. Textbook facts can be abstract. This Study of Teaching and Learning project examined the use of "non-fiction novels" (biographies and other books that read like novels but are true) in an undergraduate Sensation and Perception course in order to increase the concreteness of the reading material and to give the students a story on which to hang the facts learned in lecture.

Nucleotide polymorphisms upstream of the X-chromosome opsin gene array tune L:M cone ratio.

In support of the long-held idea that cone ratio is genetically determined by variation linked to the X-chromosome opsin gene locus, the present study identified nucleotide differences in DNA segments containing regulatory regions of the L and M opsin genes that are associated with significant differences in the relative number of L versus M cones. Specific haplotypes (combinations of genetic differences) were identified that correlated with high versus low L:M cone ratio. These findings are consistent with the biological principle that DNA sequence variations affect binding affinities for protein components of complexes that influence the relative probability that an L versus M opsin gene will be silenced during development, and in turn, produce variation in the proportion of L to M cones.

Adaptive optics retinal imaging reveals S-cone dystrophy in tritan color-vision deficiency.

Tritan color-vision deficiency is an autosomal dominant disorder associated with mutations in the short-wavelength-sensitive- (S-) cone-pigment gene. An unexplained feature of the disorder is that individuals with the same mutation manifest different degrees of deficiency. To date, it has not been possible to examine whether any loss of S-cone function is accompanied by physical disruption in the cone mosaic.

A novel mutation in the short-wavelength-sensitive cone pigment gene associated with a tritan color vision defect.

Inherited tritan color vision deficiency is caused by defects in the function of the short-wavelength-sensitive (S) cones. This heterozygous group of disorders has an autosomal dominant pattern of inheritance. Amino acid variations of the S cone opsin are rare and all that have been identified thus far are associated with inherited tritan color vision defects.

Induction effects for heterochromatic brightness matching, heterochromatic flicker photometry, and minimally distinct border: implications for the neural mechanisms underlying induction.

Brightness induction refers to the finding that the apparent brightness of a stimulus changes when surrounded by a black versus a white stimulus. In the current study, we investigated the effects of black/white surrounding stimuli on settings made between red and green stimuli on three different tasks: heterochromatic brightness matching (HBM), heterochromatic flicker photometry (HFP), and minimally distinct border (MDB). For HBM, subjects varied the relative luminance between the red and green stimuli so that the brightness of the two colors appeared equal.

Independence of mechanisms tuned along cardinal and non-cardinal axes of color space: evidence from factor analysis.

Many previous studies employing paradigms such as adaptation, masking and summation-near-threshold have demonstrated the existence of separate mechanisms underlying the detection of the three cardinal axes of color space: L+M, L-M and S-(L+M). In addition, some studies have demonstrated the existence of higher-order mechanisms tuned to non-cardinal axes (which are made up of combinations of the cardinal axes). In order to address the issue of separate and independent color mechanisms further, here we applied factor analysis to contrast threshold data obtained from 41 subjects for nine different axes in color space (the three cardinal axes and the six non-cardinal axes midway between).

Individual differences in chromatic (red/green) contrast sensitivity are constrained by the relative number of L- versus M-cones in the eye.

Many previous studies have shown that the relative number of long-wavelength-selective (L) versus medium-wavelength-selective (M) cones in the eye influences spectral sensitivity revealed perceptually. Here, we hypothesize that the L:M cone ratio should also influence red/green chromatic contrast sensitivity. To test this, in each subject we derived an estimate of L:M ratio based on her red/green equiluminance settings (obtained with heterochromatic flicker photometry), and measured both red/green chromatic and luminance contrast sensitivity at different spatial and temporal frequencies.

Surfactant replacement for ventilator-associated pneumonia: a preliminary report.

Background: Surfactant abnormalities have been described in bacterial pneumonia.

Objective: To determine the safety and effect of exogenous surfactant replacement in patients with ventilator-associated pneumonia (VAP).

Methods: Patients with VAP were randomized in a double-blind study to receive either an artificial surfactant (Exosurf) consisting mostly of disaturated phospholipids (DSPL) or saline via a continuous nebulizer system for 5 days.