bluuebunny/crossref_metadata_2025 huggingface dataset:
Visual Acuity Affected by Size Perception Based on Convergence Cue
Authors: Shinoda H , Ikeda M
Published: December 2015

Increasing (or decreasing) the convergence angle can shrink (or expand) the perceived size of an object without changing its retinal size (Oyama, 1974 Perception & Psychophysics16 175 – 182). Here we address the question whether such a change in perceived size affects visual acuity. We investigated the effects of perceived size on the legibility of letters, using a telestereoscope consisting of four mirrors to control the observer's convergence angle while keeping the size of the retinal image constant. The targets were photocopies of ordinary Japanese books containing both types of Japanese characters, kana and kanji. The former is a phonetic character and simpler than the latter. Letters were printed in black on white paper. First, we demonstrated that letters do become more legible (illegible) as perceived size expands (shrinks), although their retinal size does not change. Then, we measured the size of the convergence angle at which letters became legible. The ‘threshold’ size of the convergence angle was obtained for several retinal sizes (0.1 to 0.2 deg) of letters, and for kana and kanji, respectively.

Four subjects participated in the experiment. The result shows that the threshold convergence angle for legibility decreases as the retinal size of letters decreases, so that the minimum retinal size of legible letters depends linearly on the convergence angle. The results implicate contributions from higher levels of the visual system to the determination of visual acuity.
A Neural Network Model of Tilt Aftereffects
Authors: Bednar J A , Miikkulainen R
Published: December 2015

RF-LISSOM, a self-organising model of laterally connected orientation maps in the primary visual cortex, was used to study the psychological phenomenon known as the tilt aftereffect. The model allows observation of activation and connection patterns between large numbers of neurons simultaneously, making it possible to relate higher-level phenomena to low-level events, which is difficult to do experimentally. In RF-LISSOM, the same self-organising processes that are responsible for the development of the orientation map and its lateral connections are shown to result in tilt aftereffects over short time scales in the adult. The results give computational support for the idea that direct tilt aftereffects arise from adaptive lateral interactions between feature detectors, as has long been surmised. They also suggest that indirect effects could result from the conservation of synaptic resources during this process. The model thus provides a unified computational explanation of self-organisation and both direct and indirect tilt aftereffects in the primary visual cortex.
Highly Accurate Measurements of Human Colour Vision Parameters with Application to Diagnostics
Authors: Chistopolov A V
Published: December 2015

A new method for measuring a wide spectrum of parameters describing a subject's colour vision is presented. It is based on a portable visual colorimeter, ‘Spectr-3M’, designed in our laboratory and has several useful features: (1) it enables testing over a wide area of the chromaticity diagram; (2) it allows the use of continuously changing colour stimuli; (3) the measurement accuracy is high; (4) the testing procedure is fast and comfortable, minimising the effects caused by prolonged testing and increasing the reliability of the data.

Using this method we have revealed significant deviations from the CIE 1931 standard colorimetric observer in the colour perception of several subjects previously attested by the Rabkin and Ishihara charts as having normal perception. The data obtained by our method are more informative than results obtained with the Nagel anomaloscope, revealing not only general features of colour perception defects (as the anomaloscope), but allowing more detailed characterisation, including even small deviations from the CIE 1931 standard observer.
Critical Flicker Frequency in Auditory-Deprived Children
Authors: Krasnoperova N A
Published: December 2015

The visual system of auditory-deprived children deserves special attention since its development and functioning occur without the usual support of the auditory system which stimulates eye movements in response to sound producing objects, helps in their localisation, etc. Moreover, normally, the contributions of the visual and auditory systems to learning at school are comparable but, in the cases of complete or partial deafness, the visual system is the only or the main channel responsible for acquisition and processing of information. In a pilot study, we have found that such specific conditions of visual performance could affect some visual capabilities and indices of functioning, in particular, the critical flicker frequency (CFF). CFF was measured in 63 auditory-deprived children (aged 6 – 9 years) from special kindergartens and schools and in 92 children of the same ages from ordinary schools. The light source was a red-light-emitting diode in a dark plastic cone. Since it is known that CFF depends on the state of fatigue and other conditions, the measurements were performed at several different times of the day in each subject: in the morning before lessons, in the midday after lessons, and during the 2nd or the 3rd lesson before and after a special visual exercise lasting 15 – 20 min. It was found that auditory-deprived children differed from the control group by much larger influence of school work on CFF ( p<0.001): in the control group, the average CFF after lessons was 17% lower than before lessons whereas in the test group, the corresponding lowering was equal to 34%, ie was twice as great. Other differences were less evident or insignificant.
Spatial Extent of Masking by Sine-Wave Gratings
Authors: Babenko V V
Published: December 2015

The contrast threshold for detection of a target consisting of 1.5 periods of a sine wave was determined as a function of the number of cycles in a sinusoidal mask with the same spatial frequency and orientation. The test frequencies were 2, 4, and 8 cycles deg−1. The masks were spatial-frequency modulated so as to equate their spectral extent. Stimuli were seen monocularly in Maxwellian view at a mean luminance of 10 cd m−2. The contrast threshold in a backward masking paradigm was determined by a 2AFC staircase. Data were obtained from three subjects with normal vision.

It was found that as the number of cycles in the mask was increased, the contrast threshold fell, but only to a certain level. The full range of the threshold decrement was about 2 dB. At all the spatial frequencies tested, the final threshold level was reached with 3 cycles in the mask and then remained unaffected by a further increase in the number of cycles.

The results implicate frequency-tuned mechanisms of very restricted spatial extent. It is suggested that these may underlie processing of spatially distributed information at the post-striate stages.
Eye-Position Effects on the Visual Transfer Function
Authors: Bobrova-Evpiatieva E V
Published: December 2015

Light responses of neurons in several brain areas are affected by eye position (Andersen et al, 1990 Journal of Neuroscience10 1176 – 1196). To find out if eye position may influence contrast sensitivity, measurements were made of the spatial contrast modulation transfer function at two different eye positions: with the gaze directed straight ahead and horizontally deflected by 30 deg, respectively. Eleven gratings (1.05 – 36.8 cycles deg−1) were presented so that their retinal position was identical at both eye positions. The data obtained show a significant effect of eye position on contrast sensitivity in 4 subjects out of 8. We found a mean decrease in contrast sensitivity by 10.8% in the ‘deflected’ condition. The eye-position effect was pronounced at low (14.8%) and high (29.6%) frequencies, being insignificant at middle frequencies. The maximal sensitivity decrease observed was 62.1% at 25 cycles deg−1 in one subject. In 4 of the subjects, no significant eye-position effect was found.

Thus a horizontal deflection of the gaze direction can narrow the visual transfer function in some observers and consequently impair perception of near-threshold objects dominated by high or low spatial frequencies. Further studies will show what may account for this phenomenon: the interaction of retinal and eye position signals and/or optical changes due to compression of the eye ball.
Accuracy of Pointing to Invisible Landmarks in a Familiar Environment
Authors: Sellen K , van Veen H A H C , Bülthoff H H
Published: December 2015

Humans develop a mental representation of their environment that enables them to solve their day-to-day navigation tasks. The nature and quality of this representation can be probed experimentally by studying spatial tasks like distance and bearing estimation. We investigated pointing accuracy in an outdoor environment as part of a larger project in which we compare spatial behaviour in real environments with that in virtual environments (virtual reality).

We carried out experiments in the centre of Tübingen (ca 600 m × 400 m). Standing near one of eleven well-known landmarks, subjects had to turn a pointer in the estimated direction of each of the other ten invisible (occluded) landmarks (all ten subjects had lived in Tübingen for at least two years). The estimated directions were read by the experimenter from a hidden compass and later compared with the actual directions. This procedure was repeated from all eleven locations along the subjects' route through the town.

The mean absolute angular error of pointing was 10.8°, while the individual subject's means ranged from 9.1° to 15.0°. We found highly significant differences in pointing accuracy for the different locations; mean absolute error ranged from 6.3° to 15.8° ( n=10). Systematic asymmetries in pointing from one landmark to another and back were not found.

The pointing accuracy found in this study is clearly better than that found in most other studies, which might relate to the familiarity and the size of the environment. The apparent absence of an asymmetry in the pointing directions between two locations is consistent with the notion of a metric mental map.
Contrast Sensitivity and Visual-Field Thresholds in Patients with Thyroid Optic Neuropathy
Authors: Jankauskiene J , Lukauskiene R , Mickiene B
Published: December 2015

Thyroid optic neuropathy is one of the most troubling complications of endocrine ophthalmopathies. It is related to the degree of extraocular muscle swelling in the apex of the orbit. The purpose of this study was to investigate contrast sensitivity and visual-field thresholds in patients with thyroid optic neuropathy. We examined twenty-two patients aged 29 – 63 years (mean 45.3 years). The control group consisted of fifteen healthy persons of similar age. Contrast sensitivity was measured by means of Volkov's charts (sinusoidal gratings) at eight spatial frequencies from 17.5 to 0.46 cycles deg−1. The visual field was investigated with a static automatic perimeter (Allgan Humphrey Field Analyzer) by means of the central 30-2 threshold test. All patients underwent a complete ophthalmological examination including best corrected Snellen visual acuity, fundus copy, and proptosis measurement with the Hertel exophthalmometer. The mean proptosis of patients was 19.4 mm. Fifteen of the patients had decreased visual acuity. Contrast sensitivity at low spatial frequencies was significantly reduced in the patients. It was established that a reduction of visual-field threshold accompanies the decrease of visual acuity. Our results show that contrast sensitivity and visual-field threshold testing are very sensitive at detecting early optic neuropathy and may be a useful means of following patients after treatment.
Temporal Integration and the Masking Effect of Spatiotemporal Noise
Authors: Kukkonen H T , Rovamo J
Published: December 2015

In computer-generated spatiotemporal noise every stimulus frame contains a new static noise sample. The spectral density of white spatiotemporal noise is calculated by multiplying the squared rms contrast of noise by the product of the noise check area and the exposure duration of each noise check. When the exposure duration of each noise check is gradually increased, the spectral density of spatiotemporal noise increases, reaching its maximum when noise becomes static. In static spatial noise both stimulus and noise checks have the same duration. The signal-to-noise ratio is known to be constant at detection threshold. Detection thresholds should thus increase in proportion to the spectral density of spatiotemporal noise, which increases with the duration of the noise checks. We measured detection thresholds for stationary cosine gratings embedded in spatiotemporal noise. The exposure duration of the noise checks was increased from one frame duration to the total exposure duration of the stimulus grating. Noise was thus gradually transformed from spatiotemporal to static spatial noise. The contrast energy threshold increased in proportion to the spectral density of spatiotemporal noise up to a noise check duration found to be equal to the integration time for the stimulus grating without noise. After this, energy thresholds remained constant in spite of the increase in the spectral density of spatiotemporal noise. This suggests that the masking effect of spatiotemporal noise increases with the duration of noise checks up to the critical duration marking the saturation of the temporal integration of the signal.
Influence of Scanning Eye Movements on the Scintillating-Grid Illusion
Authors: Böhm S G , Schrauf M , Wölwer W , Wist E R
Published: December 2015

The scintillating grid is an example of a brightness contrast illusion in which bright disks are superimposed on a Hermann grid. Dark spots are perceived within the bright disks as flashing with each flick of the eye (Schrauf et al Vision Research in press). With steady fixation, stimulation must be brief for the illusion to occur. Varying exposure duration with steady fixation, we found the maximum illusion at durations between 210–350 ms (Schrauf et al, 1996 Perception25 Supplement, 78).

In the present study voluntary saccadic eye movements were used to produce brief exposures during fixations. The task of 5 trained subjects was to scan scintillation grids of five different spacings (0.5 – 2.0 deg separation of grid elements, observation time 60 s) in a manner yielding a maximum scintillating effect. Eye movements were recorded binocularly at 100 Hz with the Demel Debic 90 infrared corneal reflection tracker (resolution: 6 min arc). For each fixation we calculated latency and position. Durations and amplitudes of the saccades increased with decreasing angular separation of grid elements. When the illusion was maximal, roughly 60% of fixation durations were between 250 and 550 ms. These durations overlap with those obtained with steady fixation combined with variable exposure durations. Unlike the Hermann grid illusion, where illusory dark spots can be perceived at very brief exposure durations, the scintillating grid illusion takes much more time to develop. The long optimal durations found here are discussed in relation to mechanisms of scanning eye movements.
Altered Functions of Visual Brain Areas: Review of Recent Evidence from Blind Human Subjects
Authors: Kujala T , Alho K
Published: December 2015

We investigated the functional role of human visual brain areas deprived of visual information. To this end, we recorded brain activity elicited by auditory and somatosensory stimuli in blind human subjects. Activity was recorded in the ‘Attend’ condition, in which subjects detected occasional deviant stimuli presented among repetitive standard stimuli and in the ‘Ignore’ condition, in which subjects did not attend to the stimuli.

The results indicate that in the early-blinded subjects, event-related potential (ERP) topography elicited by deviant auditory and somatosensory target stimuli is posterior to that in the sighted (Kujala et al, 1995 Experimental Brain Research104 519 – 526). This suggests involvement of posterior brain areas in auditory and somatosensory processing in the blind humans. For the auditory modality, activated areas were located with magnetoencephalography (MEG), which indicates involvement of extrastriate occipital areas in detection of auditory targets (Kujala et al, 1995 Experimental Brain Research103 143 – 146). Visual-cortex plasticity was further studied in subjects who had lost their vision after childhood in order to clarify whether these cross-modal changes are specific to visual deprivation of early onset. In that study, auditory ERP topographies of late-blinded, early-blinded, and sighted subjects were compared. Comparison of posterior topography of ERPs elicited by deviant target stimuli in both early-blinded and late-blinded subjects with that in the sighted subjects suggests visual-cortex involvement in auditory processing even in late-onset blindness (Kujala et al, 1977 Psychophysiology34 213 – 216). Preliminary MEG recordings in one late-blinded subject provided further support for posterior generators (parietal-occipital) in auditory processing.
A Possible Role for the Antioxidants Lutein and Zeaxanthin in Protecting against Age-Related Increases in Lens Density
Authors: Hammond B R , Náñez J E
Published: December 2015

Epidemiological data have identified a number of factors that influence risk of developing age-related cataract (ARC). For instance, factors that promote (eg smoking and light exposure) and factors that protect (eg antioxidants) against oxidative stress to the crystalline lens appear to increase and decrease risk of ARC, respectively. Although biochemical studies consistently support a protective role for antioxidants, the epidemiological data are inconsistent. Since ARC is a condition with a protracted latency period, it is possible that the inconsistencies present in the epidemiological literature may be due to the focus on cataractous patients. We focused on the lens health of individuals prior to cataract. Lens health was determined by measuring the optical density (OD) of the lens with a psychophysical technique. OD characterises many of the biochemical changes of the lens and is part of many systems used to classify ARC. Variance in lens OD, stratified by age, was examined for its relationship to variables thought to be important to the etiology of ARC. We report results for the relationship of lens OD to the antioxidants lutein and zeaxanthin (L and Z). For older individuals (>48 years) we noted a significant inverse relationship between dietary intake of L and Z and lens OD ( n=39, r=−0.34, p<0.015). This was not the case for younger individuals (24 – 36 years). This relationship is increased when L and Z are measured directly in the retina is a psychophysical technique. For older individuals, retinal L and Z (ie macular pigment) are inversely related to lens OD ( n=51, r=-0.47, p<0.001). These data are consistent with a role of L and Z in protecting against age-related increases in the OD of the crystalline lens.
Spatial-Frequency Characteristics of Different Areas of Human Cortex
Authors: Harauzov A K , Shelepin Y E , Pronin S V
Published: December 2015

We recorded visual evoked potentials in normal subjects from different areas of the occipital cortex, from the temporal and parietal lobes according to the ‘ten - twenty’ electrode system. Stimuli were black-and-white sine-wave gratings with eight different spatial frequencies in the range 0.45 to 14.4 cycles deg−1, presented at four different temporal frequencies (1, 2, 4, 8 Hz). Stimulation was either contrast-reversal or onset. VEPs were analysed both by component analysis and by Fourier transformation.

Spatial characteristics were measured from the dependence of the amplitudes and latencies of the main response components (N1, P1, N2, P2) on the contrast and spatial frequency of the gratings. The characteristics obtained in the occipital lobe are in accordance with earlier experimental data [Regan, 1989 Human Electrophysiology (Amsterdam: Elsevier)]. When the temporal frequency of stimulation was increased, the maximum of the spatial-frequency curves shifted to lower spatial frequencies. However, we found differences in the spatial-frequency characteristics of different cortical areas. The results are discussed in terms of differences in the spatial and temporal tuning of the receptive fields of neurons in these areas.
Task-Dependence of Texture-Segregation-Specific VEP Components
Authors: Meigen T
Published: December 2015

Recently, texture-segregation-specific components have been isolated in the human visual evoked potential (tsVEPs). As tsVEPs are characterised by a negative peak near 200 ms they occur between luminance-contrast responses (P100) and cognitive responses (P300). The aim of this study was to estimate the temporal overlap of tsVEPs and cognitive VEP components by directing a task to either visual or auditory stimuli.

Eight visually normal subjects participated in the experiment. Horizontal and vertical line segments were arranged to yield either an ‘orientation chequerboard’ stimulus or two fields with homogeneous orientations. As auditory stimuli, two tones with different pitches were presented through headphones. Auditory and visual stimuli were temporally uncorrelated, which allowed off-line isolation of VEPs and AEPs by appropriate averaging from the same raw data. VEPs and AEPs were recorded from an array of 13 electrodes ranging from frontal to occipital positions. tsVEPs were isolated under two conditions, where the subjects detected the presence of (a) the orientation chequerboard, or (b) the higher pitch by pressing a button.

It was found that (1) tsVEPs could be isolated under both tasks; (2) tsVEPs were strongly modulated by the task; (3) the task-specific modulation occurred in the same time domain as the tsVEP itself, but showed a different topography; (4) AEPs were less modulated by the task. The data suggest that an additional task concerning the gradient content of texture stimuli may modulate the resulting tsVEPs. This may partially account for the interindividual variability in recent tsVEP data, as a comparable task may be introduced tacitly by the subjects.
Perception of the Rotation Direction in Structure from Motion Displays
Authors: Bocheva N , Stefanova M
Published: December 2015

The ability of human observers to extract the three-dimensional shape of visual objects from optic flow depends on the estimation of the characteristics of the flow. A convenient way to describe optic flow is to decompose it into translational and rotational components. Theoretical considerations [Koenderink, 1990, in Perception and Control of Self Motion Eds R Warren, A Wertheim (Hillsdale, NJ: Lawrence Erlbaum Associates)] suggest that the local orientation and shape extracted from the optic flow depend on the direction of the axis of rotation. We performed a set of experiments to evaluate the ability of human observers to determine the elevation and the azimuth of the rotation axis in structure-from-motion displays. The stimuli were pseudo-random dot patterns. The motion of the dots corresponded to the two-dimensional projections of opaque spherical, elliptical, or hyperbolic surface patches. A matching procedure was used. The results show that the estimation of the elevation is more precise and reliable than the azimuth of the rotation axis and does not depend on differences in stimulus shape or on the azimuth values. The best estimates were obtained for vertical and horizontal axes of rotation. The results are discussed in relation to the role of rotation axis evaluation for the extraction of the local shape of the three-dimensional objects, as well as to the possible mechanisms for the determination of this global characteristic of the optic flow.
Breakdown of Apparent Motion under Stereoscopic Viewing
Authors: Yukumatsu S , Bingushi K
Published: December 2015

To study the effect of binocular disparity on apparent motion, we measured the cumulative time of its breakdown during a 30 s fixation viewing period. Two light spots, both on the left side of the fixation point, were alternately presented one by one on a CRT display (unilateral condition). These spots were binocularly disparate and viewed through a stereoscope. While one spot near the fixation point was presented on a zero disparity plane, the other spot (more peripheral) was either on a zero, uncrossed, or crossed disparity plane, so that three-dimensional motion could be seen depending on disparity values. We found that the duration of the breakdown of apparent motion was longer when uncrossed and zero-disparity spots were paired to produce apparent motion, and it was shorter when crossed and zero-disparity spots were paired. However, such disparity-specific tendencies were not obtained when the two spots were presented on both sides of the fixation point (bilateral condition). The disparity-specific tendencies in the unilateral condition can be explained by assuming that three-dimensional apparent motion that is consistent with the motion perspective may be stable because we experience it more frequently. Thus, we assume that perception of motion, both apparent and real, may develop through everyday experiences of moving to and fro in the environment rather than seeing objects move.
Summation of Quantal Noise in Space and Time
Authors: Hemilä S , Lerber T , Donner K
Published: December 2015

Noise in visual neurons, or variability in psychophysical experiments, may be quantified in terms of photon fluctuations from an ‘equivalent’ steady illumination. The conversion requires assumptions on how photon signals are pooled in space and time, ie how to pass from the light flux to the numbers of photon events relevant to the Poisson statistics describing signal/noise. Real weighting profiles for the integration of photon events in space and time [the sensitivity distribution of the receptive field (RF) and the waveform of the impulse response (IR)] are commonly approximated by sharp-bordered apertures of ‘complete’, equal-weight summation of events. Such apertures based on signal equivalence cannot provide noise equivalence, however, because greater numbers of events summed with lower weights (as in reality) have lower variances than smaller numbers summed with full weight. Thus sharp-bordered apertures are necessarily smaller if defined for noise equivalence rather than for signal equivalence. We have calculated the difference for some commonly encountered RF and IR profiles. Summation areas, expressed as numbers of photoreceptors (cones or rods) contributing with equal weight, are denoted NS for signal and NN for noise, and sharply delimited summation times are correspondingly denoted tS and tN. We show that the relation in time is tN=0.6 tS to 0.7 tS for realistic quantal response waveforms of photoreceptors. In space, the relation is NN=0.5 NS for the Gaussian distribution (eg for the RF centre mechanism of retinal ganglion cells). For a photoreceptor in an electrically coupled network the difference is still greater, eg for rods in the toad retina NN=0.2 NS ( NS=13.7 rods and NN=2.8 rods). We introduce a third possible definition of sharp-bordered summation apertures: one that provides the same signal-to-noise ratio (SNR) for large-long stimuli as the real integration profiles. The SNR-equivalent summation area is N*= NS2/ NN and the summation time is t*= tS2/ tN.
2-D Affine Transformations Cannot Account for Human 3-D Object Classification
Authors: Liu Z
Published: December 2015

Converging evidence in object recognition has shown that the performance of human observers depends on their familiarity with the appearance of the objects. The degree of this dependence is a function of the inter-object similarity in the object set. The more similar the objects are, the stronger is this dependence, and the more dominant is two-dimensional (2-D) image information. However, the extent to which 3-D structural information is used still remains an area of strong debate. Previously, we showed that all models that allowed 2-D rotations in the image plane of independent 2-D templates were unable to account for human performance in recognising novel object views. Here we derive a closed-form Bayesian ideal observer that gives rise to probably the best possible performance when applying 2-D affine transformations (translation, rotation, scaling, stretching, and other linear transformations) to stored 2-D templates. In addition, we compare human performance with a closed-form derivation that finds the best match between a 2-D template and a 2-D image under 2-D affine transformations. We also compare human performance with a generalised radial basis functions model. This model establishes optimal performance for learned 2-D templates, and then adjusts the variance of its radial basis (Gaussian) functions to achieve best possible performance for novel views of individual objects. We demonstrate that none of these models can account for human performance in 3-D object recognition. Human statistical efficiency for novel views is higher than for learned views, which suggests that 3-D structural information is used by human observers.
Implication of the Yellow Pigment in Dichoptic Colour Mixing
Authors: de Mattiello M L F , Biondini A R , Salinas H
Published: December 2015

Working with colours generated from the three primaries, we found earlier that blue made it difficult to obtain dichoptic mixtures, producing chromatostereopsis and alternation effects which disappeared with increasing eccentricity (1 deg 3 min) or decreasing intensity of the blue component. The unanswered question was: is it true that mixtures with a strong blue component can never be obtained centrally as some authors claim? Therefore, we returned to this subject, using the same methodology and analysing the role that the yellow pigment (YP) would play.

First, the samples that previously produced the aforementioned effects were tested, confirming that chromatostereopsis stopped before the alternation. Immediately after that, identical samples were observed through low-density yellow filters that were superposed until both effects ceased. Since the density of the YP of the four participating observers had been previously measured, it was possible to calculate the necessary increase for each one of them, observing that the increment became smaller as the mixtures were displaced towards longer wavelengths.

This behaviour indicates a possible function of YP: the attenuation of the blue cone signal to make it compatible with signal from the red and green cones. As the YP varies among observers, this might be the reason why some sources mention that these mixtures can be obtained. If this hypothesis is accepted, this should not be interpreted as a variation in the number of blue receptors through the macula, a variation not necessarily observed in physiology.
Difference in Perceived Colour between Painted Chips and CRT Images
Authors: Hasegawa T , Iiyama R
Published: December 2015

The inducing effect of blue in colour assimilation on a CRT screen is so strong that pale blue apparently veils the stimulus pattern (Miyamoto and Hasegawa, 1996 Perception25 Supplement, 105). A similar tendency can be observed on painted paper, but this effect is not so marked. This led us to try colour matching between coloured papers and colours reproduced on a CRT screen. In both conditions the shapes (square) and the sizes (35 cm × 35 cm) were the same. They were displayed in the centre of a 155 cm × 155 cm gray (Munsell value 5, 22 cd cm−2) square with 10 cm wide white fringe (74 cd cm−2). The task was to adjust the colour on the CRT screen to match the coloured chip which was inside an illuminated box at a viewing distance of 180 cm in a dark room. Twenty-four colours were tested. Matched blues and other blue hues were slightly more saturated than object colours, but differences in chromaticity coordinates ( u‘ v’) were not statistically significant. This result is opposite to the prediction because it suggests a less bluish impression in the film-colour mode. By contrast, luminance in matched blues was lower than that of the object. This means that the brightness effect increased. An additional experiment in which the stimulus size was larger and the illuminating condition was changed to a light room produced the following results: (i) no meaningful difference in chromaticity coordinates could be seen; and (ii) the luminance of matched colours increased with size and in the lighter viewing condition. These facts show that the bluish colours on the CRT screen do not change their perceived chromaticity or spread spatially. The only difference was the subjective brightness increase in the condition when the room was dark. The strong effect of the blues in assimilation on the screen, therefore, does not depend on the colour identification process itself, but on the combined effect of luminosity and visual frequency response.
The MacKay Phenomenon: Is it All Hand-Waving?
Authors: Smith C , Lee B
Published: December 2015

When a table-tennis bat with a light-bulb in its centre is waved about by another person in a stroboscopically lit room, the light appears to float free from the bat, although it is physically fixed. A related phenomenon was reported originally by MacKay [1958 Nature (London)180 507 – 508)]. This illusion disappears in an active condition, where observers move the bat with their own hands, which suggests a proprioceptive basis for the illusion. In our implementation with a Power Macintosh computer, the illusion occurred in both conditions. Thus ‘hand-waving’ is not inherent to the illusion but may exert its effect indirectly by promoting predictive eye-tracking movements.

To test the hypothesis that the perceived position of the bulb is extrapolated between a visual icon, tied to retinal coordinates, and its actual physical location thus causing the displace-ment illusion, we performed two experiments. From experiment 1 we found that for simple one-dimensional movement, the displacement illusion occurs only when there is a change in direction such that the bulb appears to ‘overshoot’ the bat. In experiment 2, using random two-dimensional movement, we manipulated the length of the dark (non-visible) period. The overshoot increased from around 30 min arc at 65 ms to around 60 min arc at 300 ms. For longer dark periods (up to 2000 ms), the illusion occurred providing the change in direction was within the 300 ms window after stimulus offset. These results show that during discontinuous illumination, perceived location is determined by extrapolation.
Can Slip of the Retinal Image Cause Amblyopia?
Authors: Leinonen M T , Rinne P
Published: December 2015

One of the main purposes of the oculomotor system is to keep the image projected on the retina stationary in spite of the continuous movement of the head. If the vestibulo-ocular and optokinetic reflexes are defective, the retinal image becomes blurred owing to the uncoordinated movements of the head and the eyes. It is well known that in children retinal blur caused by media opacities or large refraction errors results in amblyopia. In a similar way amblyopia could be caused by slip of the retinal image due to a defective oculomotor system.

Our patient was a small for gestational age A-twin. He developed dystonic diplegia with poor head control. At the age of 7 months he was considered to have cortical visual impairment. In a magnetic resonance image of the brain there were diffuse periventricular changes in the white matter and hypoplasia of the corpus callosum and the cerebellar vermis. Binocular optokinetic reflexes to full-field stimuli were horizontally asymmetric and were missing vertically. The reflexes to rotation of the child were asymmetric in the same way. In order to stabilise the retinal image the head of the child was supported always when he was supposed to look at a target with fine details. Increase in visual acuity measured with a Teller acuity card procedure was apparent after head support. This suggests that retinal slip can cause amblyopia. It is usual practice not to support the head of a child who has cerebral palsy and poor head control. In the case of defective head - eye coordination this practice could be harmful to the normal development of vision.
Differential Activation to Faces, Degraded Faces, and Their Inverted Counterparts
Authors: Linkenkaer-Hansen K , Sams M , Hietanen J K , Ilmoniemi R J
Published: December 2015

We investigated electrophysiological correlates of activation to faces, pointillised faces (degraded to a degree still allowing face perception), and their inverted counterparts. Evoked magnetic fields to the four stimulus categories were recorded by 122-channel magnetoencephalography (MEG) in six subjects. Simultaneously recorded 64-channel EEG provided visual evoked potentials in four subjects.

Analysis of the onset, peak latencies, and the signal strength of the face enhanced N170 response indicated the following. (1) In general, the MEG and EEG recordings supported each other. (2) Degrading the images delayed both the onset and peak latencies. Degrading the upright faces increased activity in some subjects, but activity to the degraded inverted faces was lower in all subjects. (3) Inversion delayed the onset latency of both the original and degraded faces by 4 – 10 ms on average. A similar shift was found for the peak latency of the inverted original face images. However, their pointillised counterparts peaked on average 26 ms later when inverted. The signal amplitude also reflected a differential effect of inverting original vs degraded faces; whereas original faces evoked larger responses in all six subjects, the signal to inverted degraded faces decreased in four subjects. The findings suggest that the analysis of both the onset (100 – 120 ms) and peak activity (150 – 170 ms) is important for understanding face processing. The effect of inversion on the evoked responses was found to be different for the original and pointillised faces.
Illusory Contours Do Not Capture Stereopsis—They Just Constrain the Depth Spreading
Authors: Häkkinen J , Kojo I , Liinasuo M , Nyman G
Published: December 2015

If vertical cut-out sectors defining a Kanizsa square are given crossed disparity, the illusory figure appears in depth. Such an illusory figure can pull the background pattern inside the illusory figure to the same depth. It has been assumed that illusory contours are necessary for this phenomenon, which is called stereo capture (Ramachandran, 1986 Perception & Psychophysics39 361 – 373). However, we noticed that the vertical cut-out sectors of the inducing figures (‘pacmen’) are not the only structures that can capture the background texture. The rows of background dots that are enclosed between the disparate vertical cut-out sectors also have unambiguous stereoscopic depth. Thus it might be possible that the disparate rows alone capture the background texture. To investigate our hypothesis we created a stereogram in which the inducing figures were removed. It consisted of a dotted background texture and four areas devoid of dots. The dotless areas corresponded to the areas which were occluded by the original inducing figures. Because of this, the top and bottom rows inside the central area were in crossed disparity.

According to our results (a) depth capture also occurred without illusory contours; (b) when illusory contours were not present, the depth of the disparate rows spread more often to other areas. Usually the depth spread first to the central area of the figure and after that horizontally to other areas of the figure. Therefore, we conclude that illusory contours do not capture stereopsis—they just constrain the depth spreading.
A Visual-Field Anisotropy of the Filehne Illusion
Authors: Ehrenstein W H
Published: December 2015

During pursuit eye movements stationary objects are perceived to move in the direction opposite to the ocular pursuit (the Filehne illusion). The strength of this illusion, which indicates a loss of position constancy, was quantified by a cancellation method. Subjects pursued a small target that moved horizontally at 6 deg s−1 over 18 deg. When the target reached the midpoint of its trajectory, a test spot was exposed for 200 ms, either 0.5 or 1 deg above or below the target. Subjects reported the direction in which the test spot appeared to move. Test-spot speed was varied according to subject response (by means of an adaptive program Best PEST) to determine the point of subjective stationarity. This test speed was divided by the target speed to derive a percent measure of the illusion (eg 0% if no cancellation was needed, 100% if cancellation speed equalled that of pursuit). Whereas the magnitude of the Filehne illusion did not depend on the separation of the target and the test spot, it depended strongly (p<0.01) on whether the test stimulus was in the upper (26% illusion) or lower (36.5% illusion) visual field. The present anisotropy is compared to corresponding anisotropies in motion sensitivity (Ehrenstein et al, 1991 Pflügers Archiv418 R39) and pursuit velocity (Schlykowa et al, 1996 NeuroReport7 409 – 412) and conforms with a general view of a differentiation of visual and oculomotor functions between upper and lower visual fields, serving far-space and near-space orientation, respectively (Previc, 1990 Behavioral and Brian Sciences13 519 – 575).
One Eye is Usually Centred Horizontally (and near the Golden Section Vertically) in Portraits over the Past 500 Years
Authors: Tyler C W
Published: December 2015

Although the eyes are a key feature of facial portraits, compositional rules for the placement of the eyes relative to the frame are obscure. Two hypotheses of eye position in the portrait frame were compared: that the pair of eyes were symmetrically placed or that one eye was centred in the frame. Portraits were defined as paintings of a single person from the waist up without other dominant objects or animals in the scene. From all artists represented in seven source-books on portraiture over the past five centuries (eg from van Eyck to Picasso), the first portrait in which both eyes were visible was analysed (170 portraits). Horizontal and vertical eye and mouth positions were measured as a proportion of frame width and height.

The eyes in portraits tend to cluster horizontally around the centre vertical, with one eye centred in a normal distribution with a sigma of only ±5% of the frame width. The binocular mean had a bimodal distribution implying that one or other eye was usually centred. Conversely, the eye height distribution was not centred vertically but peaked close to the classic golden ratio of 0.618 (where the smaller portion has the same ratio to the larger as does the larger to the whole), with virtually no eyes below the vertical centre. The mouth distribution was much broader than that of the centred eye. The eye centring with an accuracy of ∼1 eye width seems not to be mentioned in art criticism, which suggests that unconscious functions operate in our aesthetic judgements.
Interleukin-11 alters placentation and causes preeclampsia features in mice
Authors: Winship Amy L. , Koga Kaori , Menkhorst Ellen , Van Sinderen Michelle , Rainczuk Katarzyna , Nagai Miwako , Cuman Carly , Yap Joanne , Zhang Jian-Guo , Simmons David , Young Morag J. , Dimitriadis Evdokia
Published: December 2015

Significance

Preeclampsia is an insidious disease, unique to humans, affecting ∼8% of pregnancies. There are no early detection tests or pharmacological treatments. Impaired placentation is widely accepted to contribute to the pathogenesis. However, the mechanisms remain elusive, given the complications of studying first-trimester placental development in women. A major limitation for the study of new treatments is the lack of available animal models that recapitulate the full spectrum of preeclampsia features. We have developed a mouse model characterized by elevated levels of the cytokine Interleukin-11 (IL11). This study provides evidence of a novel pathway causative of preeclampsia features in vivo
.
It also provides a novel in vivo mouse model that is useful for preclinical studies to test potential therapeutics.
Encouraging prediction during production facilitates subsequent comprehension: Evidence from interleaved object naming in sentence context and sentence reading
Authors: Hintz Florian , Meyer Antje S. , Huettig Falk
Published: December 2015

Many studies have shown that a supportive context facilitates language comprehension. A currently influential view is that language production may support prediction in language comprehension. Experimental evidence for this, however, is relatively sparse. Here we explored whether encouraging prediction in a language production task encourages the use of predictive contexts in an interleaved comprehension task. In Experiment 1a, participants listened to the first part of a sentence and provided the final word by naming aloud a picture. The picture name was predictable or not predictable from the sentence context. Pictures were named faster when they could be predicted than when this was not the case. In Experiment 1b the same sentences, augmented by a final spill-over region, were presented in a self-paced reading task. No difference in reading times for predictive versus non-predictive sentences was found. In Experiment 2, reading and naming trials were intermixed. In the naming task, the advantage for predictable picture names was replicated. More importantly, now reading times for the spill-over region were considerable faster for predictive than for non-predictive sentences. We conjecture that these findings fit best with the notion that prediction in the service of language production encourages the use of predictive contexts in comprehension. Further research is required to identify the exact mechanisms by which production exerts its influence on comprehension.
National accounts statistics of the Arab countries: selected indicators
Authors: El-Khoury Gabi
Published: December 2015

This statistical file is mainly concerned with the latest available data and estimates on gross domestic product (GDP) as one of the basic and useful indicators in assessing the economic performance in Arab countries and worldwide. Tables 1 and 2 provide figures on GDP and GDP per capita of Arab countries at current prices, while Tables 3 and 4 present estimates of GDP and GDP per capita at constant prices. Table 5 is concerned with gross national income (GNI) per capita at current prices, while Table 6 shows figures on GDP growth rates. Figures on the composition of GDP by economic sectors and on the annual change of real GDP are shown in Tables 7 and 8 respectively.
Adaptive gene- and pathway-trait association testing with GWAS summary statistics
Authors: Kwak Il-Youp , Pan Wei
Published: December 2015

Background: Gene- and pathway-based analyses offer a useful alternative and complement to the usual single SNP-based analysis for GWAS. On the other hand, most existing gene- and pathway-based tests are not highly adaptive, and/or require the availability of individual-level genotype and phenotype data. It would be desirable to have highly adaptive tests applicable to summary statistics for single SNPs. This has become increasingly important given the popularity of large-scale meta-analyses of multiple GWASs and the practical availability of either single GWAS or meta-analyzed GWAS summary statistics for single SNPs.

Results: We extend two adaptive tests for gene- and pathway-level association with a univariate trait to the case with GWAS summary statistics without individual-level genotype and phenotype data. We use the WTCCC GWAS data to evaluate and compare the proposed methods and several existing methods. We further illustrate their applications to a meta-analyzed dataset to identify genes and pathways associated with blood pressure, demonstrating the potential usefulness of the proposed methods. The methods are implemented in R package aSPU, freely and publicly available.

Availability and implementation:  https://cran.r-project.org/web/packages/aSPU/

Contact:  weip@biostat.umn.edu

Supplementary information:  Supplementary data are available at Bioinformatics online.