bluuebunny/crossref_metadata_2025 huggingface dataset:
Color scaling of discs and natural objects at different luminance
levels
Authors: HANSEN THORSTEN , GEGENFURTNER KARL R.
Published: September 2006

Assigning a basic color name to an object and rating the amount of a
particular hue is a fundamental visual capability. Traditional color
scaling studies have used increment flashes or isoluminant stimuli of a
homogeneous color. Natural objects, however, do not contain a single color
but are characterized by a distribution of different chromatic hues. Here
we study color scaling using photographs of natural fruit objects. Stimuli
were either homogeneous spots, digital photographs of fruit objects (e.g.,
banana), or outline shapes of the fruit objects. Stimuli were displayed on
a CRT monitor on a homogeneous white background; its luminance was varied
above and below the medium gray. The chromaticity of the stimuli was
varied in 36 equally spaced chromatic directions in the isoluminant plane
of the Derrington-Krauskopf-Lennie (DKL) color space. For each stimuli,
subjects rated the amount of red, green, blue, and yellow in the stimulus
on a scale from 0–8. In agreement with earlier studies we found that
the positions of the peak ratings for each color do not coincide with the
cardinal axis of DKL color space and are largely invariant under changes
of the background luminance. For the average rating we found a dependence
on background luminance for all colors: yellow ratings increase with
darker backgrounds, whereas ratings for the other colors, in particular
green, decrease. For the fruit objects, we found a selective increase in
the average color rating for the natural fruit color. For example, the
average rating for yellow was 1.7 times higher for the banana images
compared to disc stimuli. No such selective increase was found for outline
shapes. We conclude that the distribution of hues in natural objects with
a characteristic object color can have a profound effect on color scaling
and color appearance.
Paradoxical shifts in human color sensitivity caused by constructive
and destructive interference between signals from the same cone
class
Authors: STOCKMAN ANDREW , MONTAG ETHAN D. , PLUMMER DANIEL J.
Published: September 2006

Paradoxical shifts in human color (spectral) sensitivity occur on
deep-red (658 nm) background fields. As the radiance of the deep-red
background is increased from low to moderate levels, the spectral
sensitivity for detecting 15-Hz flicker shifts toward shorter wavelengths,
although by more than is predicted by selective chromatic adaptation
(e.g., Eisner & MacLeod, 1981; Stromeyer et
al., 1987; Stockman et al., 1993). Remarkably, though, at higher background
radiances, the spectral sensitivity then shifts precipitously back towards
longer wavelengths. Here, we show that both effects are due in large part
to destructive and constructive interference between signals
generated by the same cone type. Contrary to the conventional model of the
human visual system, the M- and L-cone types contribute not just the
customary fast signals to the achromatic or luminance pathway, but also
slower signals of the same or opposite sign. The predominant signs of the
slow M- and L-cone signals change with background radiance, but
always remain spectrally opposed (M-L or L-M). Consequently, when the slow
and fast signals from one cone type destructively interfere, as they do
near 15 Hz, those from the other cone type constructively interfere,
causing the paradoxical shifts in spectral sensitivity. The shift in
spectral sensitivity towards longer wavelengths is accentuated at higher
temporal frequencies by a suppression of fast M-cone signals by deep-red
fields.
Color naming, unique hues, and hue cancellation predicted from
singularities in reflection properties
Authors: PHILIPONA DAVID L. , O'REGAN J. KEVIN
Published: September 2006

Psychophysical studies suggest that different colors have different
perceptual status: red and blue for example are thought of as elementary
sensations whereas yellowish green is not. The dominant account for such
perceptual asymmetries attributes them to specificities of the neuronal
representation of colors. Alternative accounts involve cultural or
linguistic arguments. What these accounts have in common is the idea that
there are no asymmetries in the physics of light and surfaces that could
underlie the perceptual structure of colors, and this is why neuronal or
cultural processes must be invoked as the essential underlying mechanisms
that structure color perception. Here, we suggest a biological approach
for surface reflection properties that takes into account only the
information about light that is accessible to an organism given the
photopigments it possesses, and we show that now asymmetries appear in the
behavior of surfaces with respect to light. These asymmetries provide a
classification of surface properties that turns out to be identical to the
one observed in linguistic color categorization across numerous cultures,
as pinned down by cross cultural studies. Further, we show that data from
psychophysical studies about unique hues and hue cancellation are
consistent with the viewpoint that stimuli reported by observers as
special are those associated with this singularity-based categorization of
surfaces under a standard illuminant. The approach predicts that unique
blue and unique yellow should be aligned in chromatic space while unique
red and unique green should not, a fact usually conjectured to result from
nonlinearities in chromatic pathways.
Normal and dichromatic color discrimination measured with transient
visual evoked potential
Authors: GOMES BRUNO D. , SOUZA GIVAGO S. , RODRIGUES ANDERSON R. , SAITO CÉZAR A. , SILVEIRA LUIZ CARLOS L. , DA SILVA FILHO MANOEL
Published: September 2006

It would be informative to have an electrophysiological method to
study, in an objective way, the effects of mercury exposure and other
neurotoxics on human color vision performance. The purpose of the present
work was to study human color discrimination by measuring chromatic
difference thresholds with visual evoked potential (VEP). Six young normal
trichromats (24 ± 1 years old) and one deutan (26 years old) were
tested. The stimuli consisted of sinusoidal isoluminant chromatic gratings
made from chromaticity pairs located along four different color directions
centered on two reference points. Heterochromatic flicker photometry (HFP)
protocol was used to obtain the isoluminance condition for every subject
and for all chromaticity pairs. Spatial frequency was 2 cycles/deg.
Presentation mode comprised onset (300 ms)/offset (700 ms) periods. As
previously described, we found a negative deflection in the VEP which was
related to the chromatic difference: as chromatic difference increased,
amplitude increased and latency decreased. VEP response amplitude was
plotted against distance in the CIE 1976 color space between the grating
chromaticities and fitted with a regression line. We found color
thresholds by extrapolating the fitting to null amplitude values. The
thresholds were plotted in the CIE 1976 color space as MacAdam ellipses.
In normal trichromats the ellipses had small size, low ellipticity, and
were vertically oriented. In the deutan subject, the ellipses had large
size, high ellipticity, and were oriented towards the deutan copunctal
locus. The VEP thresholds were similar to those obtained using grating
stimuli and psychophysical procedures, however smaller than those obtained
using pseudoisochromatic stimuli (Mollon-Reffin method). We concluded that
transient VEP amplitude as a function of contrast can be reliably used in
objective studies of chromatic discrimination performance in normal and
altered human subjects.
Global integration of local color differences in transparency
perception: An fMRI study
Authors: DOJAT MICHEL , PIETTRE LOŸS , DELON-MARTIN CHANTAL , PACHOT-CLOUARD MATHILDE , SEGEBARTH CHRISTOPH , KNOBLAUCH KENNETH
Published: September 2006

In normal viewing, the visual system effortlessly assigns
approximately constant attributes of color and shape to perceived objects.
A fundamental component of this process is the compensation for illuminant
variations and intervening media to recover reflectance properties of
natural surfaces. We exploited the phenomenon of transparency perception
to explore the cortical regions implicated in such processes, using fMRI.
By manipulating the coherence of local color differences around a region
in an image, we interfered with their global perceptual integration and
thereby modified whether the region appeared transparent or not. We found
the major cortical activation due to global integration of local color
differences to be in the anterior part of the parahippocampal gyrus.
Regions differentially activated by chromatic versus achromatic
geometric patterns showed no significant differential response related to
the coherence/incoherence of local color differences. The results link
the integration of local color differences in the extraction of a
transparent layer with sites activated by object-related properties of an
image.
The effect of test distance on the CN lantern results
Authors: HOVIS JEFFERY K. , RAMASWAMY SHANKARAN
Published: September 2006

The purpose of this study is to determine how the viewing distance
affects the pass/fail results of the CN Lantern (CNLan). The CNLan is
a color vision test designed for the railway industry. It presents 15
triplets of colored lights that could be any combination of red, green and
yellow. The test was viewed from 4.6 m and 2.3 m. Sixty-seven
color-defectives participated in the first part of the study. Sixty-six
percent of the subjects repeated the experiment 10 days later. There was a
significant (P < 0.05) decrease in the mean number of errors
from 7.6 to 4.3 as the distance decreased. There was also a corresponding
increase in the percentage of subjects who passed from 9.0% at 4.6 m to
20.9% at the 2.3 m viewing distance. None of the subjects who passed at
the longer distance failed at the shorter distance. The replication
results were statistically identical to the first session (P >
0.05). Decreasing the CNLan viewing distance by 50% does decrease the
number of errors and increase the pass rate. This indicates that some
color-defectives could work in the railway yards where the sighting
distances for the signal lights are shorter than on the main track.
Spatial profile of contours inducing long-range color
assimilation
Authors: DEVINCK FRÉDÉRIC , SPILLMANN LOTHAR , WERNER JOHN S.
Published: September 2006

Color induction was measured using a matching method for two spatial
patterns, each composed of double contours. In one pattern (the standard),
the contours had sharp edges to induce the Watercolor Effect (WCE); in the
other, the two contours had a spatial taper so that the overall profile
produced a sawtooth edge, or ramped stimulus. These patterns were chosen
based on our previous study demonstrating that the strength of the
chromatic WCE depends on a luminance difference between the two contours.
Low-pass chromatic mechanisms, unlike bandpass luminance mechanisms, may
be expected to be insensitive to the difference between the two spatial
profiles. The strength of the watercolor spreading was similar for the two
patterns at narrow widths of the contour possibly because of chromatic
aberration, but with wider contours, the standard stimulus produced
stronger assimilation than the ramped stimulus. This research suggests
that luminance-dependent chromatic mechanisms mediate the WCE and that
these mechanisms are sensitive to differences in the two spatial profiles
of the pattern contours only when they are wide.
Induced steady color shifts from temporally varying surrounds
Authors: D'ANTONA ANTHONY D. , SHEVELL STEVEN K.
Published: September 2006

The color appearance of a physically steady central region can appear
to vary over time if a surrounding chromatic light varies in time. The
induced temporal variation, however, is strongly attenuated at surround
temporal frequencies above ∼3 Hz. At these higher temporal
frequencies, the central region appears steady (De Valois et al., 1986). The posited explanation is a cortical low-pass
temporal filter. Here, we investigate whether higher temporal-frequency
surrounds induce color shifts in the steady appearance of the
central test. Surrounds modulated in time along the l or
s chromatic direction of MacLeod-Boynton color space were
symmetric around equal-energy white (EEW). The temporal frequency of the
surround was varied. If observers perceived the central test to be
temporally modulating between two points in time, they set two separate
matches to the extreme points of this modulation. If the central test
appeared steady in time, then color matches were made to this steady
appearance. Corroborating previous reports, measurements showed that
surround temporal frequencies below ∼3 Hz induced temporal modulation.
At higher temporal frequencies, however, the surround induced steady color
shifts, compared to a steady surround at its time average (EEW). The
measurements imply that a nonlinear neural process affects chromatic
induction from time-varying context.
Response of carp (Cyprinus carpio) horizontal cells to heterochromatic flicker photometry
Authors: DE AGUIAR MARLISON JOSÉ L. , VENTURA DORA FIX , FILHO MANOEL DA SILVA , DE SOUZA JOHN MANUEL , MACIEL ROGÉRIO , LEE BARRY B.
Published: September 2006

The objective of the present work was to determine the interaction of cone inputs in the response of horizontal cells using heterochromatic flicker photometry (HFP). Intracellular electrophysiological recordings were made in horizontal cells of isolated retinae of carp maintained in physiological solution, with the receptor side up. Sharp glass microelectrodes filled with 3 M KCl solution with resistances between 100 and 120 MΩ were used. Stimuli comprised six cycles of two 6-Hz sinusoidal light waves in counterphase adjusted for the same number of quanta: a green light (550 nm) from a monochromator with a Xenon lamp and an LED red light (628 nm). The stimulation program consisted of 10 steps with the 550-nm wave at constant amplitude, while the 628-nm wave varied in increments of 10% up to 100%, followed by another 10 steps with the 628-nm wave at constant amplitude while the 550-nm wave varied in increments of 10% up to 100%. We recorded responses from four different horizontal cell classes: H1 (monophasic, broadband,n= 37), H2 (biphasic, red-green color-opponent,n= 13), and H3 (biphasic, blue-yellow color-opponent,n= 2) cone horizontal cells; and RH (monophasic, broadband,n= 3) rod horizontal cells. H1 and RH horizontal cells showed a similar cancellation point at a heterochromatic mixture consistent with mixed inputs from 630- and 550-nm cones. No cancellation point was found for the H2 cell class. Fish H1 cells add cone inputs and signal “luminance” in light levels appropriate for cone stimulation. The same occurs with RH cells, which also signal “luminance,” but in light levels appropriate for rod work. For both cell classes there is an HFP cancellation point occurring at a combination of 628-nm and 550-nm lights in opposing phase that leads to the cancellation of the cell's response. No cancellation was found for H2 and H3 cells, which are the chromatically opponent horizontal cells in lower vertebrates.
Color constancy in natural scenes with and without an explicit
illuminant cue
Authors: AMANO KINJIRO , FOSTER DAVID H. , NASCIMENTO SÉRGIO M.C.
Published: September 2006

Observers can generally make reliable judgments of surface color in
natural scenes despite changes in an illuminant that is out of view. This
ability has sometimes been attributed to observers' estimating the
spectral properties of the illuminant in order to compensate for its
effects. To test this hypothesis, two surface-color-matching experiments
were performed with images of natural scenes obtained from high-resolution
hyperspectral images. In the first experiment, the sky illuminating the
scene was directly visible to the observer, and its color was manipulated.
In the second experiment, a large gray sphere was introduced into the
scene so that its illumination by the sun and sky was also directly
visible to the observer, and the color of that illumination was
manipulated. Although the degree of color constancy varied across this and
other variations of the images, there was no reliable effect of illuminant
color. Even when the sky was eliminated from view, color constancy did not
worsen. Judging surface color in natural scenes seems to be independent of
an explicit illuminant cue.
The gap effect is exaggerated in parafovea
Authors: DANILOVA MARINA , MOLLON JOHN
Published: September 2006

In central vision, the discrimination of colors lying on a tritan line is improved if a small gap is introduced between the two stimulus fields. Boynton et al. (1977) called this a “positive gap effect.” They found that the effect was weak or absent for discriminations based on the ratio of the signals of long-wave and middle-wave cones; and even for tritan stimuli, the gap effect was weakened when forced choice or brief durations were used. We here describe measurements of the gap effect in the parafovea. The stimuli were 1 deg of visual angle in width and were centered on an imaginary circle of radius 5 deg. They were brief (100 ms), and thresholds were measured with a spatial two-alternative forced choice. Under these conditions we find a clear gap effect, which is of similar magnitude for both the cardinal chromatic axes. It may be a chromatic analog of the crowding effect observed for parafoveal perception of form.
Effects of motion and configural complexity on color transparency
perception
Authors: GERARDIN PEGGY , ROUD PHILIPPE , SÜSSTRUNK SABINE , KNOBLAUCH KENNETH
Published: September 2006

We tested whether motion and configural complexity affect perceived
transparency. A series of five coherent chromatic transformations in color
space was applied across a figure: translation, convergence, shear,
divergence and rotation. The stimuli consisted of a bipartite or a
checkerboard configuration (10 × 10°), with a central static or
moving overlay (5 × 5°). Three different luminance conditions
(the plane of chromatic transformation oriented toward higher, lower, or
equal luminances) were also tested for each of three modulation depths.
For each stimulus, the observer judged whether the overlay appeared
transparent or not. The main results indicated an interaction between the
type of chromatic transformation and stimulus motion and complexity. For
example, convergences are judged to appear transparent significantly more
often when motion is added for bipartite configurations, or when they are
generated in a checkerboard configuration. Surprisingly, shears that have
been reported to appear opaque, are more frequently reported to appear
transparent with short vector lengths and when combined with motion. Other
transformations are also affected by motion, although the effectiveness of
figural complexity on transparency seems to depend on both the type of
color shifts and the presence of motion. The results indicate that adding
motion and stimulus complexity are not necessarily neutral with respect to
the chromatic shifts evoking transparency. Thus, studies that have used
motion to enhance transparency may yield different results about the color
shifts supporting transparency perception from those that did not. The
same might be supposed for stimulus complexity under some conditions.
Hyperoxia, hyperglycemia, and photoreceptor sensitivity in normal
and diabetic subjects
Authors: KURTENBACH ANNE , MAYSER HELMUT M. , JÄGLE HERBERT , FRITSCHE ANDREAS , ZRENNER EBERHART
Published: September 2006

The aim of this study was to investigate the effects of an increase in
the saturation of blood oxygen (SaO2) and/or serum glucose
on photoreceptor sensitivity in normal subjects and in patients with
diabetes mellitus. We monitored cone and rod sensitivity by recording
dark-adaptation curves to both green and red test stimuli while inhaling
either air (20% O2 + 80% N2) or 100% oxygen in 12
normal subjects and 12 diabetic patients with no (10) or mild (2)
retinopathy. We also repeated the experiment in 10 of the normal subjects
under hyperglycemia (mean serum glucose: 161 mg/dl). Results show that
in normal subjects the dark-adapted cone sensitivity is improved by an
increase in SaO2 or by hyperglycemia. Final rod sensitivity is
unchanged during hyperoxia and during hyperglycemia when measured with a
green test spot. However the kinetics of dark adaptation are altered
during hyperglycemia, and an increase in final sensitivity is observed
when measured with the red test spot. Inhalation of oxygen during
hyperglycemia in normal subjects reduces cone sensitivity compared to that
found during hyperglycemia alone (Pasteur effect). In diabetic subjects
the dark-adapted cone threshold is comparable to that found in normal
subjects, and sensitivity also increases with an increase in
SaO2. The final rod threshold, however, is impaired compared to
that of the control group, and rod sensitivity is improved by increasing
the SaO2. The results suggest that the metabolism of rods and
cones may differ in normal subjects: in cones, the rate of metabolism can
be augmented by increasing the available oxygen or glucose, whereas rods
appear more insensitive to increased blood oxygen saturation and
hyperglycemia. In diabetic subjects, both cone and rod metabolism can be
increased by supplemental oxygen, indicative of an early rod deficit. The
study lends weight to the hypothesis that dark-adapted rods in diabetics
are hypoxic before the onset of retinopathy.
The discoloration illusion
Authors: PINNA BAINGIO
Published: September 2006

The discoloration illusion, a new visual phenomenon, is
described. This phenomenon originates from the juxtaposition of eight
chromatic parallel contours on a white background, creating a luminance
gradient and enclosing a light red region. Under these conditions, the
inner region appears white: the light red discolors and appears white with
both surface color and luminous qualities. In two experiments, the
discoloration illusion was (i) compared with the coloration effect of the
watercolor illusion, obtained when the number of adjacent contours was
reduced to at least two, and (ii) tested under several conditions useful
for understanding the roles of the luminance gradient profile. The results
suggest that discoloration is not a lightness illusion and does not depend
on simultaneous contrast or on achromatic mechanisms, but more likely on
chromatic mechanisms that, through the luminance chromatic gradient,
provide cues about the interactions of light and surface and model the
volume by depicting lights and shades. The discoloration illusion suggests
a possible neural scenario where multiple juxtaposed contours may
stimulate neurons, selective for different asymmetric luminance profiles
and signaling not only the unilateral belongingness of the boundaries and
the coloration effect but also the volumetric and the illumination
effects.
Surface color perception in three-dimensional scenes
Authors: BOYACI HUSEYIN , DOERSCHNER KATJA , SNYDER JACQUELINE L. , MALONEY LAURENCE T.
Published: September 2006

Researchers studying surface color perception have typically used stimuli that consist of a small number of matte patches (real or simulated) embedded in a plane perpendicular to the line of sight (a “Mondrian,” Land & McCann, 1971). Reliable estimation of the color of a matte surface is a difficult if not impossible computational problem in such limited scenes (Maloney, 1999). In more realistic, three-dimensional scenes the difficulty of the problem increases, in part, because the effective illumination incident on the surface (the light field) now depends on surface orientation and location. We review recent work in multiple laboratories that examines (1) the degree to which the human visual system discounts the light field in judging matte surface lightness and color and (2) what illuminant cues the visual system uses in estimating the flow of light in a scene.
Color stimuli perception in presence of light scattering
Authors: OZOLINSH MARIS , COLOMB MICHÉLE , IKAUNIEKS GATIS , KARITANS VARIS
Published: September 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 corresponding to the blue, green, and red color contributions in achromatic white stimuli (computer digital R, G, or B values for chromatic stimuli equal to RGB values in the achromatic white background) that results in the greatest luminance contrast for the white–blue stimuli, thus advancing the visual acuity for the white-blue stimuli. Besides such blue stimuli on the white background are displayed with a uniform, spatially unmodulated distribution of the screen blue phosphor emission over the entire area of the screen including the stimulus C optotype area. It follows that scattering, which has the greatest effect on the blue component of screen luminance, has the least effect on the perception of white–blue stimuli.
Visual sensitivity to color errors in images of natural scenes
Authors: ALDABA MIKEL A. , LINHARES JOÃO M.M. , PINTO PAULO D. , NASCIMENTO SÉRGIO M.C. , AMANO KINJIRO , FOSTER DAVID H.
Published: September 2006

Simple color-difference formulae and pictorial images have traditionally been used to estimate the visual impact of color errors introduced by image-reproduction processes. But the limited gamut of RGB cameras constrains such analyses, particularly of natural scenes. The purpose of this work was to estimate visual sensitivity to color errors introduced deliberately into pictures synthesized from hyperspectral images of natural scenes without gamut constraints and to compare discrimination thresholds expressed in CIELAB and S-CIELAB color spaces. From each original image, a set of approximate images with variable color errors were generated and displayed on a calibrated RGB color monitor. The threshold for perceptibility of the errors was determined in a paired-comparison experiment. In agreement with previous studies, it was found that discrimination between original and approximate images needed on average a CIELAB color difference ΔEab* of about 2.2. Although a large variation of performance across the nine images tested was found when errors were expressed in CIELAB units, little variation was obtained when they were expressed in S-CIELAB units.
Monge: The Verriest Lecture, Lyon, July 2005
Authors: MOLLON JOHN
Published: September 2006

In 1789, when neither the physical basis of hue nor the retinal basis of color perception was established, the mathematician Gaspard Monte stated firmly that our color perceptions do not depend on the absolute value of the physical variable, but are influenced by the context and in particular by our estimate of the illuminant. He used this insight to explain color contrast effects and the Paradox of Monge (the desaturation of red objects seen through a red filter). He proposed that we can estimate the chromaticity of the illuminant in any scene because all surfaces reflect to us varying mixtures of (i) the body color and (ii) a specular component that represents the illuminant. He also realized that white objects have a special property: Provided that they are illuminated by a single illuminant, such objects exhibit no variation in chromaticity across their surface. Thus at least one of the unique hues exists as an external reference on which observers can agree. It is suggested that other unique hues may also have a basis in the external world.
Foveal and extra-foveal influences on rod hue biases
Authors: THOMAS LAURA P. , BUCK STEVEN L.
Published: September 2006

Green, blue and short-wavelength-red rod hue biases are strongest and most reliable with large, dimly-mesopic, extra-foveal stimuli but tend to diminish when stimuli are confined to a small area of the central fovea. This study explores how the stimulation of foveal and extra-foveal areas interact in determining rod hue biases, and whether large stimuli are as effective for revealing rod hue biases when foveally centered as when eccentrically centered. We assessed rod influence by measuring wavelengths of unique green and unique yellow (with 1-s duration, 1 log scot td stimuli and a staircase procedure) under bleached and dark-adapted conditions. We measured unique hues with foveally centered 2°- and 7.4°-diameter disks, a 7.4° (outer) × 2° (inner) diameter annulus, and a 7°-eccentric, 7.4°-diameter disk. The rod green bias (shift of unique yellow locus) was typically <10 nm and remained fairly constant across spatial configurations, indicating no special foveal influence. The rod blue bias (shift of unique green) varied more among observers and spatial configurations, reaching up to 47 nm. However, stimuli covering the fovea typically produced no rod blue bias. Thus, the present results add differences in spatial dependence (i.e., foveal/extra-foveal interaction) between green and blue rod biases to previously demonstrated differences (e.g., differences in amount of light level dependence, in time course and in the spectral range influenced by each bias).
Temporal nulling of induction from spatial patterns modulated in
time
Authors: AUTRUSSEAU FLORENT , SHEVELL STEVEN K.
Published: September 2006

Temporally varying chromatic-inducing light was used to infer
receptive-field organization. Time-varying shifts in color appearance
within a test field were induced by a surrounding chromatic pattern; the
shifts were then nulled by adding a time-varying stimulus to the test area
so the observer perceived a steady test. This method measured chromatic
induction without requiring an observer to judge the color appearance of
the test. The induced color shifts were consistent with a
+s/−s spatially antagonistic neural receptive
field, which also accounts for color shifts induced by static chromatic
patterns (Monnier & Shevell, 2003, Monnier
& Shevell, 2004). The response of this type
of receptive-field, which is found only in the visual cortex, increases
with S-cone stimulation at its center and decreases with S-cone
stimulation within its surround. The measurements also showed a negligible
influence of temporal inducing frequency in the range 0.5–4 Hz.
Color naming and categorization in inherited color vision
deficiencies
Authors: BONNARDEL VALÉRIE
Published: September 2006

Dichromatic subjects can name colors accurately, even though they
cannot discriminate among red-green hues (Jameson & Hurvich, 1978). This result is attributed to a normative
language system that dichromatic observers developed by learning subtle
visual cues to compensate for their impoverished color system. The present
study used multidimensional scaling techniques to compare color
categorization spaces of color-vision deficient (CVD) subjects to those of
normal trichromat (NT) subjects, and consensus analysis estimated the
normative effect of language on categorization. Subjects sorted 140
Munsell color samples in three different ways: a free sorting task
(unlimited number of categories), a constrained sorting task (number of
categories limited to eight), and a constrained naming task (limited to
eight basic color terms). CVD color categories were comparable to those of
NT subjects. For both CVD and NT subjects, a common color categorization
space derived from the three tasks was well described by a
three-dimensional model, with the first two dimensions corresponding to
reddish-greenish and yellowish-bluish axes. However, the third axis, which
was associated with an achromatic dimension in NTs, was not identified in
the CVD model. Individual differences multidimensional scaling failed to
reveal group differences in the sorting tasks. In contrast, the personal
color naming spaces of CVD subjects exhibited a relative compression of
the yellowish-bluish dimension that is inconsistent with the typical
deutan-type color spaces derived from more direct measures of perceptual
color judgments. As expected, the highest consensus among CVDs (77%) and
NTs (82%) occurred in the naming task. The categorization behaviors
studied in this experiment seemed to rely more on learning factors, and
may reveal little about CVD perceptual representation of colors.
The Kosovo Trap
Authors: BEREND IVAN T.
Published: September 2006

In February 2006, talks began in Vienna to decide the status of Kosovo. The solution was forecast in several statements: instead of officially remaining a province of Serbia, considering that 90% of the population of the area is Albanian, mostly Muslim, and want independence, independent statehood might be granted to Kosovo. Kosovo enjoyed an autonomous status under Tito (abolished by Milošević) and thus has the legal right to decide on independence.

Serbia wants to keep its authority over the province, which is considered to be the ‘cradle of Serbia,’ a sacrosanct place in Serbian history. However, the Serb population has gradually decreased and become a small minority. This happened due to a huge Serb emigration after the Ottoman conquest of the region, a spontaneous, sometimes forced emigration, which gained special impetus during the Second World War, when the region became part of ‘Great Albania,’ and Serbs were killed and chased out of the province. The tension and violence of the post-war decades made emigration advisable for Serbs. Milošević's Kosovo war-and-rape campaign made the Kosovars victims of exalted Serb nationalism in the late 1990s. The NATO bombing stopped this but the Serb minority declined into an unbearable situation. The Kosovo Liberation Army's violent actions, killing Serbs, burning their houses, shooting at school buses, continued until recently and led to the flight of half of the remaining Serb population, and ‘cleansed’ Kosovo of 80% of the Roma population.
The First Wave of International War Crimes Trials: Istanbul and Leipzig
Authors: KRAMER ALAN
Published: September 2006

The Nuremberg tribunal following the Second World War is universally considered as the foundation stone of international law with regard to war crimes and crimes against humanity. It may come as a surprise, however, to learn that the first international attempts to prosecute war crimes and crimes against humanity came at the end of the First World War, with trials held at Allied prompting in Turkey and Germany.
Labour Market Flexibility: Need and Outcome. Some Socio-economic Reflections based on the European Experience
Authors: URBAN SABINE M.-L. , VELO DARIO
Published: September 2006

The fast rate of the globalisation process and huge technological changes are leading to increased uncertainty. Risk (considered either as a threat or as an opportunity) is correlated to uncertainty. That means that the socio-economic environment may be considered as ambiguous, and the reaction of players complex, unforeseeable and difficult to handle. In such conditions one looks for simple formulae or tricks to manage the necessary change in human behaviour, institutional structures, production and trade methods. ‘Flexibility’ seems to be a magic keyword – both a performance driver and an expression of freedom. Labour market flexibility is currently the focus of ideological and political debate. This paper aims to clarify some points in the debate, especially in the European Union context. First, we give some brief information about the EU framework with regard to the labour market flexibility and its performance. Second, we try to understand how labour market flexibility is dependent on decisions of enterprises (in search of competitiveness). But this point of view needs to be enlarged to a more systemic approach; flexibility is only one of the socio-economic performance variables. A flexibility paradigm is related to a new political and humanistic project, and is a serious consideration for a number of industrial and financial companies, scientific associations and bodies.
Self-regulation and social and behavioral functioning following childhood traumatic brain injury
Authors: GANESALINGAM KALAICHELVI , SANSON ANN , ANDERSON VICKI , YEATES KEITH OWEN
Published: September 2006

This study examined the impact of childhood traumatic brain injury (TBI) on self-regulation and social and behavioral functioning, and the role of self-regulation as a predictor of children's social and behavioral functioning. Participants included 65 children with moderate to severe TBI and 65 children without TBI, all between 6 and 11 years of age. Self-regulation and social and behavioral functioning were assessed 2 to 5 years following injury. Children with TBI displayed deficits in self-regulation and social and behavioral functioning, after controlling for socioeconomic status (SES), although the magnitude of the deficits was not related to injury severity. Self-regulation accounted for significant variance in children's social and behavioral functioning, after controlling for SES and group membership. Self-regulation may be an important determinant of children's social and behavioral functioning following TBI. (JINS, 2006,12, 609–621.)
Motivational processes and autonomic responsivity in Asperger's
disorder: Evidence from the Iowa Gambling Task
Authors: JOHNSON SHANNON A. , YECHIAM ELDAD , MURPHY ROBIN R. , QUELLER SARAH , STOUT JULIE C.
Published: September 2006

Asperger's disorder (ASP), like other autism spectrum disorders,
is associated with altered responsiveness to social stimuli. This study
investigated learning and responsiveness to nonsocial, but motivational,
stimuli in ASP. We examined choice behavior and galvanic skin conductance
responses (SCRs) during the Iowa Gambling Task (IGT; Bechara et al., 1994) in 15 adolescents and young adults with ASP and
14 comparison subjects. We examined aspects of learning, attention to wins
and losses, and response style with a formal cognitive model, the
Expectancy–Valence Learning model (Busemeyer & Stout, 2002). The ASP group did not differ from the
comparison group in proportions of selections from advantageous decks.
However, ASP participants showed a distinct pattern of selection
characterized by frequent shifts between the four IGT decks, whereas
comparison participants developed clear deck preferences. SCR results
showed some evidence of reduced responsiveness in the ASP group during the
IGT. Results from the cognitive model indicated that, in contrast to the
comparison group, the ASP group's selections were less consistent
with the motivational significance they assigned to decks. Findings are
discussed in the context of the neurobiological substrates associated with
IGT performance (JINS, 2006, 12, 668–676.)
Detection of inadequate effort on the California Verbal Learning
Test-Second edition: Forced choice recognition and critical item
analysis
Authors: ROOT JAMES C. , ROBBINS REUBEN N. , CHANG LUKE , VAN GORP WILFRED G.
Published: September 2006

The Forced Choice Recognition (FCR) and the Critical Item Analysis
(CIA) indices of the California Verbal Learning Test-II (CVLT-II) have
been identified by the CVLT-II test developers as potentially useful,
brief screening indicators of effort in neuropsychological assessment.
This retrospective study analyzes performance on these measures in three
groups: (1) clinically referred individuals; (2) forensically referred
individuals not suspected of inadequate effort; and (3) forensically
referred individuals whose performance on freestanding tests of effort
suggested inadequate effort. Performances on FCR were analyzed for their
relation to actual memory impairment and with regard to concrete and
abstract distractor endorsement. FCR and CIA performances were analyzed
for agreement with formal tests of inadequate effort and their test
characteristics. Incremental validity was assessed by hierarchical
logistic regression with previously identified indices for detection of
inadequate effort on the CVLT. Results indicate that (1) FCR and CIA
performances are not related to decreased memory performance; (2) FCR and
CIA indices exhibit higher specificity and lower sensitivity, with higher
positive predictive value than negative predictive value; and (3) FCR and
CIA indices exhibit modest incremental validity with previously identified
indices. Implications for use of FCR and CIA indices in inadequate effort
detection are discussed (JINS, 2006, 12,
688–696.)
Impulsivity, reward sensitivity, and decision-making in subarachnoid
hemorrhage survivors
Authors: SALMOND CLAIRE H. , DEVITO ELISE E. , CLARK LUKE , MENON DAVID K. , CHATFIELD DORIS A. , PICKARD JOHN D. , KIRKPATRICK PETER J. , SAHAKIAN BARBARA J.
Published: September 2006

Subarachnoid hemorrhage (SAH) survivors often report psychosocial and
emotional changes, including a diminished capacity for decision making.
However, systematic investigations into the nature of the changes have
been limited to those patients surviving SAH secondary to aneurysms of the
anterior communicating artery. This study aimed to explore the nature of
decision making in survivors of SAH secondary to aneurysms of the middle
cerebral or posterior communicating artery using a series of computerized
tasks. Twenty SAH survivors and 20 matched controls completed a battery of
computerized decision-making tasks. These included tasks examining an
individual's ability to make probabilistic choices and risk-taking
behavior, as well as tasks examining aspects of impulsivity. The results
revealed two key patterns of abnormal decision-making behavior in the SAH
survivors: altered sensitivity to both reward and punishment, and
impulsive responding. These complex deficits may contribute to
difficulties in daily living resulting from apathy, poor judgment, or
inhibition in SAH survivors. (JINS, 2006, 12,
697–706.)
The impact of sleep deprivation and task difficulty on networks of fMRI brain response
Authors: STRICKER JOHN L. , BROWN GREGORY G. , WETHERELL LESLEY A. , DRUMMOND SEAN P.A.
Published: September 2006

Previous fMRI research has found altered brain response after total sleep deprivation (TSD), with TSD effects moderated by task difficulty. Specific models of the impact of sleep deprivation and task difficulty on brain response have yet to be developed. Differences in networks of fMRI measured brain response during verbal encoding in sleep deprived and well-rested individuals were examined with structural equation modeling (SEM). During fMRI scanning, 23 healthy volunteers memorized words either easy or difficult to recall, 12 (well-rested) and 36 hours (sleep deprived) after awaking.A priorimodels that linked specified regions of interest were evaluated, with the focus on the extent to which two left parietal regions interacted with the left inferior frontal gyrus (Model 1) or with the right inferior frontal gyrus (Model 2). Task difficulty, not TSD, determined which model fit the brain response data; Model 2 fit best for hard words before and after TSD, whereas Model 1 fit best for easy words. TSD altered the patterns of interaction within each of the best fitting models: prefrontal interactions with the left inferior parietal lobe were diminished and intra-parietal interactions increased. Sleep deprivation and item difficulty produce different effects on brain networks involved in verbal learning. (JINS, 2006,12, 591–597.)
Neuropsychological and neuroimaging changes in preclinical Alzheimer's disease
Authors: TWAMLEY ELIZABETH W. , ROPACKI SUSAN A. LEGENDRE , BONDI MARK W.
Published: September 2006

Alzheimer's disease (AD) is a common, devastating form of dementia. With the advent of promising symptomatic treatment, the importance of recognizing AD at its very earliest stages has increased. We review the extant neuropsychological and neuroimaging literature on preclinical AD, focusing on longitudinal studies of initially nondemented individuals and cross-sectional investigations comparing at-risk with normal individuals. We systematically reviewed 91 studies of neuropsychological functioning, structural neuroimaging, or functional neuroimaging in preclinical AD. The neuropsychological studies indicated that preclinical AD might be characterized by subtle deficits in a broad range of neuropsychological domains, particularly in attention, learning and memory, executive functioning, processing speed, and language. Recent findings from neuroimaging research suggest that volume loss and cerebral blood flow or metabolic changes, particularly in the temporal lobe, may be detected before the onset of dementia. There exist several markers of a preclinical period of AD, in which specific cognitive and biochemical changes precede the clinical manifestations. The preclinical indicators of AD reflect early compromise of generalized brain integrity and temporal lobe functioning in particular. (JINS, 2006,12, 707–735.)
Assessing everyday action in dementia: A response to de Jonghe
(2006)
Authors: GIOVANNETTI TANIA
Published: September 2006

The Cognitive Neuropsychology Laboratory at Temple University applies
neuropsychological models of action processes to the study of everyday
action (EA) in dementia. Our ultimate goals are to develop models of EA
impairment and inform interventions that promote EA in the home. Our
recent paper (Giovannetti et al., 2006b) was an
initial step in this overarching plan. We examined differences in EA
between participants with Alzheimer's disease (AD)
versus Vascular dementia (VaD), two distinct neurocognitive
syndromes (see Libon et al., 2004). The groups
obtained comparable overall accomplishment scores, but VaD participants
made more commissions and accomplished fewer steps when distractor objects
were in the workspace. Thus, VaD participants demonstrated a different
pattern of EA impairment than AD participants.
A Contemporary Approach to Geriatric Neuropsychology
Authors: Barr William B.
Published: September 2006

Geriatric Neuropsychology: Assessment and Intervention.
Deborah K. Attix and Kathleen Welsh-Bohmer (Eds.). 2006. New York: The
Guilford Press, 467 pp., $65.00 HB.

Most neuropsychologists specializing in assessment and treatment of
adults will receive a fair share of referrals for assessment of memory and
cognitive functions in older patients. The past 15 to 20 years have been
marked by an impressive increase in the amount known about the
neurobiological basis of aging and dementia. Keeping up with this field
has been like monitoring a “moving target,” as a result of
increasing refinements in diagnostic categories, technological
developments in neuroimaging, and continuing discoveries in the fields of
genetics and molecular biology. The field has needed an accessible
reference that reviews all of these important areas while also providing
an integration of the literature from a uniquely neuropsychological
perspective. I am pleased to report that the book, Geriatric
Neuropsychology: Assessment and Intervention, meets this important
need.