bluuebunny/crossref_metadata_2025_split huggingface dataset:
Flicker Fusion Frequency in Ophthalmic Express-Diagnosis
Authors: Golubtsov K V , Orlov O Y 
Published: December 2015

The critical flicker fusion frequency (CFF) for full-field illumination is an easily accessible measure for evaluating the functional state of the visual system. A decrease of the CFF is a symptom of some disorder and reason for medical care. Owing to the great number of components of the visual system (which includes the retina, neural pathways, and visual centres), however, diagnosis based on this single measure may be rather uncertain. This is possibly the reason why the diagnostic value of the CFF seems to be underestimated and why corresponding devices are not represented among everyday health evaluation procedures. We suggest a simple and convenient (even though not precise) device for CFF testing, useful for express-diagnosis of (i) general visual fatigue due to visual strain and (ii) abnormalities related to ophthalmopathology, implying the need of medical care. The simplicity and convenience of the device make it appropriate for monitoring, for example, school pupils in classrooms. A toy-like modification of the device enables testing of pre-school children. The diagnostic value of simple devices can be increased if the functional differences (relevant to the CFF: colour, movement, etc) of distinct parts of the human visual system are taken into account. Their deviations from the norm can be especially useful for selective diagnosis in some cases. This may be considered when developing further devices for simple express-diagnosis of ophthalmic diseases.
Two New Dynamic Effects: Light Explosion and Night Crash
Authors: Zavagno D , Caputo G 
Published: December 2015

Starting from an achromatic display used by Zavagno to study a glare and a ‘smoke’ effect, we show two new dynamic effects that we call (a) ‘light explosion’ and (b) ‘night crash’. On a uniform white or black background four black or white rectangles (inducers, 1 deg × 5.7 deg) were arranged to form an orthogonal cross with a square gap in its centre. (a) When the luminance of black inducers on a white background is transformed into a smooth gray scale gradient with the lighter ends facing the square gap, a luminous mist with a glare effect is seen. When such a transformation is performed dynamically by changing the gradient from outside to inside (with the outside ends remaining black and the inside changing toward white), a sudden explosion of light is seen. (b) When the luminance of white inducers on a black background is transformed into a smooth gray scale gradient with their darker ends facing the square gap, a sort of dark ‘smoke’ is seen. If such a transformation is performed dynamically by changing the gradient from inside to outside (with the outside ends remaining white and the inside changing toward black), a sudden and instantaneous black diffusion (a sort of night crash) is seen. Both the light explosion and the night crash effects have an exponential course followed by an immediate drop. Psychophysical data show that both effects depend on an interaction between the lightness of the background, the lightness of the square gap, and the transformation rate of the gray scale gradient.
Is Rotation of Visual Mental Images a Motor Act?
Authors: Wexler M 
Published: December 2015

The relationship between the mechanisms of vision and of visual mental imagery, such as mental rotation, has been well established. The relations between mental rotation and motor action, on the other hand, have hardly been studied, despite the fact that, ecologically, most non-mental rotation is the result of motor actions such as manual manipulation of medium-sized objects. I propose the following motor/imagery hypothesis: transformations of visual mental images are functionally closely related to the planning stages of the motor system. There is a certain amount of indirect support for this hypothesis in the literature. In the present work the motor/imagery hypothesis was tested directly, by means of a dual task paradigm. Subjects performed two tasks simultaneously: the Shepard - Cooper visual imagery task, which involves mental rotation; and a motor rotation (which could not be seen), turning a joystick handle in the plane of the visual image at a previously learned angular speed and direction. The motor/imagery hypothesis predicts a correlation between corresponding features of the two rotations. The results strongly confirm the motor/imagery hypothesis. The concurrent motor task shifts the classic V-shaped mental rotation RT curve: mental rotation is faster and less error-prone when it is in the same direction as the motor rotation than when it is in the opposite direction. Moreover, there is a strong correlation between the speeds of the two rotations: all else being equal, subjects' mental rotations were slower when their manual rotations were slower, and vice versa.
Retinal Mechanisms Underlying Pedestal Effects in Brightness Discrimination: A Model
Authors: Donner K , Hemilä S 
Published: December 2015

The dependence of the minimal discriminable intensity difference (MDD) of two flashed stimuli on the pedestal (the intensity of the dimmer one) is known to follow a nonmonotonic ‘dipper’ function. When the pedestal is zero, the MDD is by definition identical to the threshold for light detection. Very dim pedestals have little effect on the MDD, but there is a range of fairly dim pedestals, of intensities around the detection threshold, where the MDD decreases with increasing intensity. Beyond that range, the MDD is a monotonically increasing function of intensity. Functions of this type have been observed with spatially very different stimuli. We propose that dipper functions arise owing to the fact that different aspects of the primary light response of photoreceptors are relevant to near-threshold and suprathreshold visual signals. Decisions near the detection threshold are based on signals determined by the peak amplitude of photoreceptor responses, which for dim stimuli grows linearly with intensity. By contrast, visual signals for clearly suprathreshold stimuli reflect the rate of rise of early parts of the photoreceptor response, tracing only a short segment of the photoreceptor response just after the point where it has reached threshold amplitude. The latter type of signal shows a similar intensity dependence as do psychophysical brightness judgments, starting with a supralinear segment and passing via linearity into a compressive power function at high stimulus intensities (Donner, 1989 Visual Neuroscience3 39 – 51; Djupsund et al, 1996 Vision Research36 3253 – 3264). Discrimination sensitivity is in principle proportional to the derivative of this function. The transition from the ‘peak-amplitude-based’ linear signalling range around detection threshold to the ‘early-rise-based’ signalling range described by the nonlinear brightness function implies a sharp contraction of the response time window. Intensity discrimination improves, because the intensity dependence of the signal scaled by its variability becomes steeper than linear. As pedestal intensity is raised further, however, the MDD begins to increase again, basically in inverse proportion to the decreasing derivative of the brightness function.
Deafness and Attentional Visual Search: A Developmental Study
Authors: Marendaz C , Robert C , Bonthoux F 
Published: December 2015

Neurophysiological (epigenetic specialisation of cortical areas) as well as behavioural (sign language, visual control of spatial surroundings) constraints suggest that deaf people should develop heightened abilities of processing parafoveal/peripheral visual information. Electrophysiological (visual event-related potentials) and psychophysical research using visual detection tasks on congenitally deaf adults corroborates this viewpoint (Neville, 1994 The Cognitive Neurosciences 219 – 231). The aim of this study was to examine whether this ability remains when the visual detection task requires a spatiotemporal organisation of attention. Forty congenitally bilaterally deaf (from a specialised institution) and sixty-four hearing subjects, subdivided into five age groups (from 7 years of age to young adults) performed four visual search tasks. The results showed that the younger deaf children performed dramatically worse than the aged-matched hearing children. This difference in performance between deaf and hearing children, however, disappeared at an age level of 11 years. Deaf adults did not perform significantly better than hearing adults. The data obtained in children have been replicated in a longitudinal study (re-test two years after). We are currently trying to determine which attentional mechanisms are more deficient in young deaf children (spatiotemporal organisation of search, engagement/disengagement of attention, etc) and what underlies the apparent amelioration of their deficit during development.
The Stereokinetic Phenomenon from Two or Three Points
Authors: Komatsu H 
Published: December 2015

The stereokinetic phenomenon occurs when certain 2-D patterns are rotated in the frontoparallel plane. Zanforlin explained this phenomenon by the hypothesis of the minimisation of velocity differences. Our visual system minimises relative velocity differences between the various points of the pattern, which determines the apparent height of the stereokinetic cone. Zanforlin and Vallortigara applied the hypothesis to a rotating straight line or the two end-points of a straight line. They showed that the apparent length of the line does not depend on the absolute physical velocities of the end-points but rather on the relative velocities, and the absolute physical velocities merely affect the apparent position of the line with respect to the plane of the disk. In the present experiments with two points, the apparent length indeed depended on the relative velocities, but the absolute velocities did not affect the apparent position. The apparent position of the line with respect to the plane of the disk depended on whether or not the centre of rotation was between the two end-points. Adding one more point gave a triangle that appeared slanted into 3-D space. The shape composed of three points was held constant, even when rotated and slanted. The height of the apparent triangle also depended on the relative velocities.
Experimental Evaluation of the Reliability of the Method of Constant Stimuli
Authors: Dubrovskii V E , Lovi O V 
Published: December 2015

Although the method of constant stimuli is commonly used in psychophysical investigations, special statistical procedures for testing its reliability are rarely employed. Measurement errors are usually ignored, and their potential effect on the overall efficiency of the measurement procedure is not taken into consideration. In reality, the decision-making strategy of the subject may change during the course of the experiment, and responses may be correlated. We suggest a completely nonparametric method for testing hypotheses about a subject's decision-making strategy. It is based on the analysis of contingency tables and includes the method of primary-data grouping. This technique was applied to address two questions: (1) whether the results of a set of experiments, conducted independently of each other, may be considered as statistically equivalent; (2) whether the subject's response depends statistically on his preceding decisions. Specially designed experiments on discrimination of the length of lines were performed with a large number of untrained subjects. Exploratory analysis of primary data typical for experiments of this kind has revealed some features that are usually not detected by ordinary statistical data processing, but may affect the final results. It appeared that untrained subjects often used a decision-making strategy biased towards the preceding response. This does not seem to be dependent on the personal characteristics of the subject. Some psychophysical procedures in fact encourage subjects to use this strategy.
Chromatic Cues for Face Detection in Natural Scenes
Authors: Oliva A , Akamatsu S , Schyns P G 
Published: December 2015

One of the challenging problems of human and machine vision is the detection of objects against complex backgrounds. Our research addresses the question of how faces can be very quickly detected in naturalistic scenes on the basis of luminance and chromatic cues. Although luminance information varies with pose and illumination differences, chromatic information is by and large invariant under these transformations. Hence, chromatic information might be a very powerful cue for segmentation and detection. We compared faces of different pigmentation against background scenes of different colours. Specifically, colour histograms were computed in a perceptually uniform colour space (L*u*v*). We computed the Euclidian distances between the averages of the colour histograms of faces and scenes in L*u*v*. This metric was used to calibrate the contrast between face and scene colour in the experimental design. In a face detection task, subjects saw faces against scene backgrounds at a different distance in colour space. Each combination face - scene was presented for 120 ms (to prevent saccadic explorations), and the subject's task was to indicate whether or not a face was present. Controls involved face - scene pairs on an isoluminant background. Results revealed that luminance information did not affect detection on the basis of chromatic cues. Importantly, the metric of detectability in L*u*v* space between scene and faces predicted reaction times to detection.
Fusion of Visual and Proprioceptive Information about Hand Position Prior to Movement
Authors: Desmurget M , Rossetti Y , Prablanc C 
Published: December 2015

The problem whether movement accuracy is better in the full open-loop condition (FOL, hand never visible) than in the static closed-loop condition (SCL, hand only visible prior to movement onset) remains widely debated. To investigate this controversial question, we studied conditions for which visual information available to the subject prior to movement onset was strictly controlled. The results of our investigation showed that the accuracy improvement observed when human subjects were allowed to see their hand, in the peripheral visual field, prior to movement: (1) concerned only the variable errors; (2) did not depend on the simultaneous vision of the hand and target (hand and target viewed simultaneously vs sequentially); (3) remained significant when pointing to proprioceptive targets; and (4) was not suppressed when the visual information was temporally (visual presentation for less than 300 ms) or spatially (vision of only the index fingertip) restricted. In addition, dissociating vision and proprioception with wedge prisms showed that a weighed hand position was used to program hand trajectory. When considered together, these results suggest that: (i) knowledge of the initial upper limb configuration or position is necessary to plan accurately goal-directed movements; (ii) static proprioceptive receptors are partially ineffective in providing an accurate estimate of the limb posture, and/or hand location relative to the body, and (iii) visual and proprioceptive information is not used in an exclusive way, but combined to furnish an accurate representation of the state of the effector prior to movement.
Motion Integration over Time and Space
Authors: Takahashi N , Groner R 
Published: December 2015

The effect of temporal and spatial overlap on globally coherent motion was studied. Two lines oriented 60° and 300°, respectively, moved horizontally, creating the perception of either an integrated coherent motion on the horizontal axis, or two distinct component motions orthogonal to each line. The overlap of presentation time was varied: 100% (simultaneous), 50% (partial overlap), and 0% (successive). With respect to the spatial condition, the two lines were presented (1) superimposed in a single aperture, (2) in two adjacent apertures, or (3) in two distant apertures. We found that, when the lines were presented simultaneously, the percentage of perceived coherent motion was consistently high, regardless of spatial condition. However, when temporal overlap was lower, the percentage of perceived coherent motion decreased according to the number of apertures and their distance. In the 0% condition there were fewer than 50% coherent motions reported, even in the single-aperture condition. An effect of the intersection of the two lines was observed in the 50% condition, but not in the 100% condition. These and other findings suggest that timing is the most critical factor, and spatial effects, as expressed by the distance between the lines and by the intersections, play a less important role.
Visual Motion Induces Effector Movement
Authors: Nattkemper D 
Published: December 2015

A left-hand response to a left-hand stimulus is faster than a right-hand response to the same stimulus, even when spatial location is irrelevant to the task at hand. The existence of this spatial stimulus-response correspondence effect suggests that spatial properties of actions to be performed can be pre-specified by spatial properties of perceived events, so that actions are induced by perceptual content. If this view is correct, one should be able to show that not only spatial positions of actions can be pre-specified by properties of perceived events, but other features of actions as well. Specifically, I attempt to show that the direction of a to-be-executed movement can be specified by the direction of a moving stimulus. To study this question a variant of the Simon paradigm was developed: subjects were required to monitor a spot-like stimulus moving from left to right or from right to left on a display. At some point in time the spot would change its colour (from white to blue or red) and the subject had to respond differentially to the respective colour. Two aspects of this situation were varied. First, the type of the action-relevant signal was varied: it could either be a dynamic moving signal or a static non-moving one. Second, the type of response was varied: subjects were required to respond to the colour either with a dynamic response (moving a stylus to the left or right) or with a more static response (pressing a button on the left or on the right).
Recognition Model with Extension Fields
Authors: Kalocsai P , Biederman W I 
Published: December 2015

A recognition model which defines a measure of shape similarity on the direct output of multiscale and multiorientation Gabor filters does not manifest qualitative aspects of human object recognition of contour-deleted images in that: (a) it recognises recoverable and nonrecoverable contour-deleted images equally well, whereas humans recognise recoverable images much better; (b) it distinguishes complementary feature-deleted images whereas humans do not. Adding some of the known connectivity patterns of the primary visual cortex to the model in the form of extension fields (connections between collinear and curvilinear units) among filters (a) increased the overall recognition performance of the model, (b) boosted the recognition rate of the recoverable images far more than of the nonrecoverable ones, (c) increased the similarity of complementary feature-deleted images, but not part-deleted ones. These correspond more closely to human psychophysical results. Interestingly, performance was approximately equivalent for narrow (±15 deg) and broad (±90 deg) extension fields.
Vection with Degraded Real-World Stimuli
Authors: Ohmi M 
Published: December 2015

Psychophysical studies have revealed that the retinal periphery plays a dominant role in inducing vection, ie the visually induced sensation of self-motion. This suggests that the quality of the visual stimulus is not an important factor for vection. However, since abstract stimuli were used in these studies, it is not clear whether the quality of real-world visual stimuli could still play a critical role in inducing vection. We investigated how vection induced by real-world visual stimuli was affected when the stimuli were spatially or temporally degraded. Stereoscopic video clips were taken through the windshield of a car driven on a sharply curved and hilly road. These clips were degraded spatially by using a mosaic effect, or temporally by using a strobe effect on a video editing system. The perceived direction and strength of vection were measured while subjects were viewing these visual stimuli presented on a 63 deg wide and 38 deg high video projection monitor. Degradation of the visual stimuli was found to have little effect on the assessment of direction in horizontal vection. Assessment of the direction of vertical vection, however, was significantly disturbed by both spatial and temporal degradation of the stimuli. Temporal degradation reduced the strength of vection significantly for both horizontal and vertical motion. In contrast, although spatial degradation of visual stimuli reduced the strength of vection in both dimensions slightly, the effect was not statistically significant. We conclude that the spatial quality of real-world visual stimuli does not play a significant role in inducing vection.
Active Visual Examination of Static and Dynamic Autostereograms: Effects of Performance in a Visuomotor Task
Authors: Sergeichev O P , Levashov O V 
Published: December 2015

The purpose of our experiments was to investigate whether visual perception could be influenced by extended presence ‘inside’ a 3-D virtual reality of computer-generated autostereograms (AST). In addition to usual ASTs (with stationary hidden figures, words, and 3-D surfaces) we used novel, dynamic autostereograms (DASTs), generated in a 3-D studio as a short film, where consecutive frames were ASTs with small modifications of the disparity values. The percept resembled textured ‘mushrooms’ rising towards the observer from the main frontal plane. When the disparity rose to some limiting value, the growth stopped and was inverted: a convexity was gradually transformed into a concavity and vice versa. The maximum range of local disparity change was ±0.6 deg. Our ASTs and DASTs were arranged in a sequence of increasing complexity. During a ‘training’ session (3 – 15 min), the subject had to actively examine the sequence and recognise all hidden forms. Performance in threading a needle with one (the right) hand was recorded before and after ‘training’. The needle was set at a 50 cm distance from the subject, turned so that the eye of the needle was not visible. The total time of five successful trials was measured for each of five right-handed subjects with normal or corrected vision. In two sets of experiments, this visuomotor task was carried out under binocular and monocular viewing, respectively. In both conditions, performance improved significantly (Fisher's criterion) after the ‘training’ session. The total time decreased from 50 – 55 s to 35 – 40 s in the binocular condition and from 70 – 75 s to 47 – 55 s in the monocular condition. The results are discussed in terms of ‘tuning’ of vergence eye movements during autostereogram examination.