Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Vision Disparity”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 397 records · Page 22Linked to original sources
PubMed2006

Systematic perceptual distortion of 3D slant by disconjugate eye movements.

When an observer pursues an object moving away from him or her, both eyes rotate in the opposite direction, and this type of disconjugate eye movement can generate eye movement-induced disparities in the case of dynamic objects that are present around the pursuit object. Such disparities are not usually generated by conjugate eye movement. The aim of this study was to determine whether eye movement-induced disparities could be calibrated with eye position information. Observers were requested to judge the slant of an object defined by the spatiotemporal pattern of occlusion during disconjugate eye movement. Interestingly, the observers' perception of the slant of the target object was systematically distorted, although the perceptual distortion decreased somewhat in the presence of a salient reference around the target. This suggests that eye movement-induced disparities are not calibrated properly with eye position information.

Eye Movements↗
PubMed2006

Short-latency disparity vergence eye movements: a response to disparity energy.

Vergence eye movements were elicited in human subjects by applying disparities to square-wave gratings lacking the fundamental ("missing fundamental", mf). Using a dichoptic arrangement, subjects viewed gratings that were identical at the two eyes except for a phase difference of 1/4 wavelength so that, based on the nearest-neighbor matches, the features and the 4n+1 harmonics (5th, 9th, etc.) all had binocular disparities of one sign, whereas the 4n-1 harmonics (3rd, 7th, etc.) all had disparities of the opposite sign. Further, the amplitude of the ith harmonic was proportional to 1/i. Using the electromagnetic search coil technique to record the positions of both eyes indicated that the earliest vergence eye movements elicited by these disparity stimuli had ultra-short latencies (minimum, <65 ms) and were always in the direction of the most prominent harmonic, the 3rd, but their magnitudes fell short of those elicited when the same disparities were applied to pure sinusoids whose spatial frequency and contrast matched those of the 3rd harmonic. This shortfall was evident in both the horizontal vergence responses recorded with vertical grating stimuli and the vertical vergence responses recorded with horizontal grating stimuli. When the next most prominent harmonic, the 5th, was removed from the mf stimulus (creating the "mf-5" stimulus) the vertical vergence responses showed almost no shortfall-indicating that it had been almost entirely due to that 5th harmonic-but the horizontal vergence responses still showed a small shortfall, at least with higher contrast stimuli. This small shortfall might represent a very minor contribution from higher harmonics and/or distortion products and/or a feature-based mechanism. We conclude that the earliest disparity vergence responses-especially vertical-were strongly dependent on the major Fourier components of the binocular images, consistent with early spatial filtering of the monocular visual inputs prior to their binocular combination as in the disparity-energy model of complex cells in striate cortex [Ohzawa, I., DeAngelis, G. C., & Freeman, R. D. (1990). Stereoscopic depth discrimination in the visual cortex: neurons ideally suited as disparity detectors. Science, 249, 1037-1041].

Computer Graphics↗
PubMed1989

Disparity curvature and the perception of three-dimensional surfaces.

BINOCULAR stereopsis provides information about the relative distance of objects from the differences in the horizontal position of their images on the two retinas. Because the size of the disparity between two points is inversely related to the square of the viewing distance, it is usually assumed that disparities have to be scaled according to distance using the vergence angle of the eyes, or by using the small vertical disparities that also exist between corresponding points of the two images. Here we present evidence that the visual system could extract information about the shapes of surfaces (without the need for scaling) by using the second spatial derivative of disparity--disparity curvature--which remains invariant with viewing distance. Rather than computing the second derivative, we suggest that an approximation to disparity curvature could be derived from the differences in curvature of corresponding line elements in the two eyes.

Discrimination, Psychological↗
PubMedDate not supplied

Modeling V1 neuronal responses to orientation disparity.

The contribution of interocular orientation differences to depth perception, at either the neuronal or the psychophysical level, is unclear. To understand the responses of binocular neurons to orientation disparity, we extended the energy model of Ohzawa et al. (1990) to incorporate binocular differences in receptive-field orientation. The responses of the model to grating stimuli with interocular orientation differences were examined, along with the responses to random dot stereograms (RDS) depicting slanted surfaces. The responses to combinations of stimulus orientations in the two eyes were left-right separable, which means there was no consistent response to the binocular orientation difference. All existing neuronal data concerning orientation disparity can be well described by this type of model (even a version with no disparity selectivity). The disparity sensitive model is nonetheless sensitive to changes in RDS slant, although it requires narrow orientation bandwidth to produce substantial modulation. The disparity-insensitive model shows no selectivity to slant in this stimulus. Several modifications to the model were attempted to improve its selectivity for orientation disparity and/or slant. A model built by summing several disparity-sensitive models showed left-right inseparable responses, responding maximally to a consistent orientation difference. Despite this property, the selectivity for slant in RDS stimuli was no better than the simple disparity-selective model. The range of models evaluated here demonstrate that interocular orientation differences are neither necessary nor sufficient for signaling slant. In contrast, within the framework of the energy model, positional disparity sensitivity appears to be both necessary and sufficient.

Animals↗
PubMed1995

Immediate saccade amplitude disconjugacy induced by unequal images.

We tested the ability of normal subjects to make changes in the conjugacy of their saccades. Subjects dichoptically viewed a grid the size of which was 10% larger in one eye. The grids were centred onto a flat screen at 57 cm or 1 m from the subject. Horizontal saccades immediately became larger in the eye viewing the larger grid. For some subjects this disconjugacy persisted even under subsequent monocular viewing. Such persistent changes occurred mainly in the field where the required disconjugacy was divergent for centrifugal saccades, convergent for centripetal saccades. Vertical saccades also developed compensatory disconjugacy; its amplitude was smaller but less variable. To explain these results we propose a fast associative learning mechanism that pairs peripheral disparity with saccades and is capable of producing saccade disconjugacy even in the absence of disparity. For horizontal saccades a secondary conditioning of monocular depth cues by the disparity would also be involved.

Adult↗
PubMed2006

3D shape discrimination using relative disparity derivatives.

Three-dimensional (3D) shape discrimination could be achieved using relative disparity signals or it could be achieved using a higher-order disparity derivative detector. Two 3D shape discrimination tasks were used to distinguish between these possibilities: a within-shape task and a between-shape task. Disparity thresholds were larger when discriminating within the same shape than when discriminating between shapes. More importantly, within-shape discriminations were dependent on the pedestal disparity (distance from fixation) whereas between-shape discriminations were not. The results suggest that a mechanism sensitive to higher-order disparity derivatives can achieve discrimination between different 3D shapes.

Discrimination, Psychological↗
PubMed1999

Fixation disparity and nonius bias.

Fixation disparity, i.e. the vergence error within Panum's area, can be measured psychophysically with two nonius (vernier) lines that are presented dichoptically, i.e. one to each eye. The observer adjusts these nonius lines to subjective alignment; the resulting physical nonius offset indicates the amount of fixation disparity. The present experiments investigate the relation between fixation disparity and the nonius bias, which is the physical offset of the nonius lines that is adjusted by the observer in order to perceive them as aligned when both nonius lines are presented to both eyes (binocular nonius bias) or both to the left or both to the right eye (monocular nonius bias). It was found that (1) the fixation disparity is correlated with the binocular nonius bias in the horizontal and vertical meridian and (2) the binocular nonius bias can be predicted from the average of the right eye and left eye monocular nonius bias. To remove the influence of the nonius bias on measured fixation disparity it is possible to calculate the fixation disparity relative to the individual binocular nonius bias, rather than to the physical coincidence of the nonius lines. This procedure tends to increase the correlation between fixation disparity and the tonic resting position of vergence. We discuss the clinical relevance of the dichoptic nonius method for measuring fixation disparity and its limitations as compared to physical recordings of eye position.

Convergence, Ocular↗
PubMed2002

Influences of motion and depth on brightness induction: an illusory transparency effect?

To experiments were performed to investigate whether motion and binocular disparity influence brightness induction, and whether the effects of motion and binocular disparity, if any, interact with each other. In order to introduce motion, textured backgrounds were used as the inducing field. The results showed that motion and/or crossed disparity reduce brightness induction, whereas uncrossed disparity increases it. The effect of motion and the effect of disparity are independent of each other and additive, which suggests that, to the extent that brightness induction reflects segmentation of objects, motion and binocular disparity serve independently to segment objects from their background. The difference between the effects of crossed and uncrossed disparity can be explained by what we call 'illusory transparency'.

Analysis of Variance↗
PubMed1989

Influence of extraocular muscle imbalance on binocular performance.

In assessing binocular performance, it is possible that extraocular coordination is more significantly involved than presently recognized. Dynamic phorometry or phorometric testing in the nine cardinal directions of gaze is advised for evaluating the extraocular muscular system. These case reports used interrelation of phorias to evaluate binocular problems. The interpretation of these data helps determine the amount of horizontal prism necessary to reduce compensating vergences. Although a control group was not used, the elimination of associated vertical fixation disparity in these cases seemed to ameliorate binocular stress.

Aniseikonia↗
PubMed1997

Relationship between binocular disparity and motion parallax in surface detection.

The ability to detect surfaces was studied in a multiple-cue condition in which binocular disparity and motion parallax could specify independent depth configurations. On trials on which binocular disparity and motion parallax were presented together, either binocular disparity or motion parallax could indicate a surface in one of two intervals; in the other interval, both sources indicated a volume of random points. Surface detection when the two sources of information were present and compatible was not better than detection in baseline conditions, in which only one source of information was present. When binocular disparity and motion specified incompatible depths, observers' ability to detect a surface was severely impaired if motion indicated a surface but binocular disparity did not. Performance was not as severely degraded when binocular disparity indicated a surface and motion did not. This dominance of binocular disparity persisted in the presence of foreknowledge about which source of information would be relevant.

Humans↗
PubMed1993

How is depth perception affected by long-term wearing of left-right reversing spectacles?

The plasticity of binocular depth perception was investigated. Six subjects wore left-right reversing spectacles continuously for 10 or 11 days. On looking through the spectacles, the relation between the direction of physical depth (convex or concave) and the direction of binocular disparity (crossed or uncrossed) was reversed, but other depth cues did not change. When subjects observed stereograms through a haploscope and were asked to judge the direction of perceived depth, the directional relation between perceived depth and disparity was reversed both in the two line-contoured stereograms and in the random-dot stereogram in the middle of the wearing period, but the normal relation often returned late in the wearing period. When subjects observed two objects while wearing the spectacles and were asked which appeared the nearer, veridical depth perception increased as the wearing-time passed. These results indicate that the visual transformation reversing the direction of binocular disparity causes changes both in binocular stereopsis and in processes integrating different depth cues.

Depth Perception↗
PubMed2005

Retinal correspondence of monocular receptive fields in disparity-sensitive complex cells from area V1 in the awake monkey.

PURPOSE: To explore the neural mechanisms underlying disparity sensitivity in complex cells of the macaque visual cortex, the relationship between interocular receptive field (RF) positional shift and disparity sensitivity was studied in area V1. METHODS: Single-unit recordings were made from area V1 of awake Macaca mulatta. Monocular RFs were mapped by means of a reverse cross-correlation technique, and their centers were determined after performing a bidimensional Gaussian function fitting. Interocular RF shifts were calculated for both bright and dark stimuli. Similarly, Gabor adjustments were obtained from disparity profiles to bright and dark dynamic random-dot stereograms (RDSs). RESULTS: Twenty-five complex cells were studied. The response profiles to disparity were similar for bright and dark RDSs. Interocular RF positional shift correlated significantly with both the peaks of Gabor fittings of disparity-sensitivity profiles and the peaks of the Gaussian envelopes of these Gabor fittings. Correlation between interocular RF positional shift and the peaks of the Gaussian envelopes was stronger than correlation between interocular RF positional shift and peaks of Gabor fittings. CONCLUSIONS: Interocular shift of monocular RFs is more related to the center of the range of disparities to which the cell is sensitive, than to the preferred disparity of the cell.

Animals↗
PubMed2002

Adaptations and deficits in the vestibulo-ocular reflex after third nerve palsy.

OBJECTIVE: To analyze the vestibulo-ocular reflex (VOR) in patients with unilateral peripheral third nerve palsy. PARTICIPANTS AND METHODS: Ten patients and 15 healthy subjects were studied using magnetic search coils. Subjects made sinusoidal +/-10 degrees head-on-body rotations in yaw, pitch, and roll in darkness and during monocular viewing in light. RESULTS: Horizontal VOR and visually enhanced VOR (VVOR) gains of the paretic eye were decreased during both abduction and adduction. Vertical VOR and VVOR gains of the paretic eye were decreased during both elevation and depression. Dynamic and static torsional VOR and VVOR gains of the paretic eye were reduced during both excyclotorsion and incyclotorsion. Horizontal, vertical, and torsional VOR and VVOR gains were normal in the nonparetic eye. CONCLUSIONS: Adducting VOR gains were reduced as anticipated from medial rectus palsy. Abducting gains were also reduced; the reduction is attributed to an adaptive decrease in innervation to the lateral rectus to achieve symmetry of the horizontal VOR in the paretic eye. Torsional VOR gains were reduced during excyclotorsion from palsy of the inferior oblique muscle. Gains were also reduced during incyclotorsion, which can be explained by an adaptive decrease in innervation to the superior oblique to restore symmetry of the torsional VOR in the paretic eye. CLINICAL RELEVANCE: Monocular adaptation in the VOR of the paretic eye reduces asymmetrical movement of retinal images during head motion, prevents nystagmus, and reduces retinal image disparity.

Adaptation, Ocular↗
PubMed1996

Stability of binocular depth perception with moving head and eyes.

We systematically analyse the binocular disparity field under various eye, head and stimulus positions and orientations. From the literature we know that certain classes of disparity which involve the entire disparity field (such as those caused by horizontal lateral shift, differential rotation, horizontal scale and horizontal shear between the entire half-images of a stereogram) lead to relatively poor depth perception in the case of limited observation periods. These classes of disparity are found to be similar to the classes of disparities which are brought about by eye and head movements. Our analysis supports the suggestion that binocular depth perception is based primarily (for the first few hundred milliseconds) on classes of disparity that do not change as a result of ego-movement.

Depth Perception↗
PubMed1999

Adapting to expansion increases perceived time-to-collision.

We used a tracking method to measure errors in estimating absolute time-to-collision caused by adapting to an expanding target. After adaptation, the estimated time-to-collision was longer than in the baseline condition. This was the case whether estimates were based on binocular information alone or monocular information alone. Estimates of time-to-collision were lengthened by 8-16% when based on binocular information alone, and by 18-25% when based on monocular information alone. These findings are consistent with a previous proposal that changing-size and changing-disparity information converge before the stage at which motion-in-depth signals are generated.

Adaptation, Psychological↗
PubMed1998

[Fixation disparity with the Pola pointing test: not representative for eye position under natural viewing conditions].

BACKGROUND: According to certain findings obtained with the Zeiss Polatest, H.J. Haase defined a "Fixation Disparity Type One". In this diagnosis, the "Zeigertest" is particularly important. The Zeigertest consists of a central ring presented to both eyes for fixation, a vertical clock hand presented to the right eye and two markings at the six and twelve o'clock positions presented to the left eye. All parts are surrounded by a binocularly visible frame. Subjects with a "Fixation Disparity Type One" see a misalignment between the clock hand and the peripheral markings. We investigated (1) whether the perceived misalignment correlated with an objective deviation of the eyes from orthovergence and (2) whether subjects with a "Fixation Disparity Type One" had a deviation of the eyes from orthovergence when looking at a natural, i.e., fully fusionable object. SUBJECTS AND METHODS: Out of 303 medical students, 10 subjects with a "Fixation Disparity Type One" were selected and asked to indicate the perceived alignment or misalignment in the Zeigertest with a laser pointer. Two subjects without fixation disparity served as controls. The position of both eyes was recorded using the search coil technique. One of the 10 subjects with "Fixation Disparity Type One" had to be excluded due to excessive blinking. Experiment 1: In the beginning all parts of the Zeigertest were presented to both eyes (natural viewing condition). Then, the object for one of the eyes was switched off leaving the frame as the only fusional stimulus. The outcome variable was a refixation movement of the other eye. This experiment is similar to the unilateral cover test. Experiment 2: In the beginning all parts of the Zeigertest were presented to both eyes (natural viewing condition). Then, the original Zeigertest was switched on (clock hand presented only to the right eye, peripheral markings only to the left eye). The outcome variable was a change of vergence. RESULTS: Experiment 1: A significant refixation movement did not occur in any of the subjects. Experiment 2. In all 9 subjects with "Fixation Disparity Type One" the vergence changed significantly between 2.4 and 14.9 arcmin. The change of vergence correlated significantly with the angle of the perceived misalignment between clock hand and peripheral markings. CONCLUSION: A fixation disparity ascertained at the Zeigertest does not indicate a fixation disparity under natural viewing conditions.

Adult↗
PubMed1994

A transparent motion aftereffect contingent on binocular disparity.

Under transparent motion conditions overlapping surfaces are perceived simultaneously, each with its own direction. The motion aftereffect (MAE) of transparent motion, however, is undirectional and its direction is opposite to that of a sensitivity-weighted vector sum of both inducing vectors. Here we report a bidirectional and transparent MAE contingent on binocular disparity. Depth (from retinal disparity) was introduced between two patterns. A fixation dot was presented at zero disparity, that is, located between the two adaptation patterns. After adaptation to such a stimulus configuration testing was carried out with two stationary test patterns at the same depths as the preceding moving patterns. For opposite directions a clear transparent MAE was perceived. However, if the adaptation directions were orthogonal the chance of a transparent MAE being perceived decreased substantially. This was subject dependent. Some subjects perceived an orthogonal transparent MAE whereas others saw the negative vector sum-an integrated MAE. In addition the behavior of the MAE when the distance in depth between adapting and test patterns was increased was investigated: it was found that the visibility of the MAE then decreased. Visibility is defined in this paper as: (i) the percentage of the trials in which MAEs are perceived and (ii) the average MAE duration. Both measures decreased with increasing distance. The results suggest that segregation and integration may be mediated by direction-tuned channels that interact with disparity-tuned channels.

Contrast Sensitivity↗
PubMed2003

Eye movements facilitate stereo-slant discrimination when horizontal disparity is noisy.

Conditions in which saccadic gaze shifts within planar surfaces facilitate stereo-slant discrimination for slant about the horizontal and vertical axis were investigated. When horizontal disparity noise was added, large gaze shifts in the direction of the slant lowered stereo-slant discrimination thresholds compared to thresholds measured with steady central fixation, whereas eye movements orthogonal to the slant orientation did not lower slant-discrimination thresholds. When no horizontal noise was added, performance was the same with and without gaze shifts. These results suggest that slant is recovered from depth differences between target edges when horizontal disparity signals are variable and that foveal fixation improves the measures of disparity. Eye movements did not lower slant thresholds by providing multiple foveal samples of slant at different target locations that were averaged to reduce disparity noise levels, because eye movements only lowered the thresholds when there was a depth difference between the fixation points. To study which signals for azimuth are used when slant is recovered from the difference in depth between target edges, vertical disparity noise was added and stimulus height was reduced. Both methods elevated slant-discrimination thresholds when horizontal disparity noise was present, suggesting that vertical disparity is used as a cue for azimuth.

Depth Perception↗