Binocular Cues Research Articles

Cue integration outside central fixation: A study of grasping in depth

We assessed the usefulness of stereopsis across the visual field by quantifying how retinal eccentricity and distance from the horopter affect humans' relative dependence on monocular and binocular cues about 3D orientation. The reliabilities of monocular and binocular cues both decline with eccentricity, but the reliability of binocular information decreases more rapidly. Binocular cue reliability also declines with increasing distance from the horopter, whereas the reliability of monocular cues is virtually unaffected. We measured how subjects integrated these cues to orient their hands when grasping oriented discs at different eccentricities and distances from the horopter. Subjects relied increasingly less on binocular disparity as targets' retinal eccentricity and distance from the horopter increased. The measured cue influences were consistent with what would be predicted from the relative cue reliabilities at the various target locations. Our results showed that relative reliability affects how cues influence motor control and that stereopsis is of limited use in the periphery and away from the horopter because monocular cues are more reliable in these regions.

Impaired distance perception and size constancy following bilateral occipitoparietal damage

Accurate distance perception depends on the processing and integration of a variety of monocular and binocular cues. Dorsal stream lesions can impair this process, but details of this neurocognitive relationship remain unclear. Here, we tested a patient with bilateral occipitoparietal damage and severely impaired stereopsis. We addressed four related questions: (1) Can distance and size perception survive limitations in perceiving monocular and binocular cues? (2) Are egocentric (self-referential) and allocentric (object-referential) distance judgments similarly impaired? (3) Are distance measurements equally impaired in peripersonal and extrapersonal space? (4) Are size judgments possible when distance processing is impaired? The results demonstrate that the patient's lesions impaired both her distance and size perception, but not uniformly. Her performance when using an egocentric reference frame was more impaired than her performance when using an allocentric reference frame. Likewise, her distance judgments in peripersonal space were more impaired than those in extrapersonal space. The patient showed partial preservation in size processing of novel objects even when familiar size cues were removed.

A comparison of visuomotor cue integration strategies for object placement and prehension

Visual cue integration strategies are known to depend on cue reliability and how rapidly the visual system processes incoming information. We investigated whether these strategies also depend on differences in the information demands for different natural tasks. Using two common goal-oriented tasks, prehension and object placement, we determined whether monocular and binocular information influence estimates of three-dimensional (3D) orientation differently depending on task demands. Both tasks rely on accurate 3D orientation estimates, but 3D position is potentially more important for grasping. Subjects placed an object on or picked up a disc in a virtual environment. On some trials, the monocular cues (aspect ratio and texture compression) and binocular cues (e.g., binocular disparity) suggested slightly different 3D orientations for the disc; these conflicts either were present upon initial stimulus presentation or were introduced after movement initiation, which allowed us to quantify how information from the cues accumulated over time. We analyzed the time-varying orientations of subjects' fingers in the grasping task and those of the object in the object placement task to quantify how different visual cues influenced motor control. In the first experiment, different subjects performed each task, and those performing the grasping task relied on binocular information more when orienting their hands than those performing the object placement task. When subjects in the second experiment performed both tasks in interleaved sessions, binocular cues were still more influential during grasping than object placement, and the different cue integration strategies observed for each task in isolation were maintained. In both experiments, the temporal analyses showed that subjects processed binocular information faster than monocular information, but task demands did not affect the time course of cue processing. How one uses visual cues for motor control depends on the task being performed, although how quickly the information is processed appears to be task invariant.

Response Modes Influence the Accuracy of Monocular and Binocular Reaching Movements

The authors manipulated the availability of monocular and binocular vision during the constituent planning and control stages of a goal-directed reaching task. Furthermore, trials were completed with or without online limb vision to determine whether monocular- or binocular-derived ego-motion cues influence the integration of visual feedback for online limb corrections. Results showed that the manipulation of visual cues during movement planning did not influence planning times or overall kinematics. During movement execution, however, binocular reaches--and particularly those completed with online limb vision--demonstrated heightened endpoint accuracy and stability, a finding directly linked to the adoption of a feedback-based mode of reaching control (i.e., online control). In contrast, reaches performed with online monocular vision produced increased endpoint error and instability and demonstrated reduced evidence of feedback-based corrections (i.e., offline control). Based on these results, the authors propose that the combination of static (i.e., target location) and dynamic (i.e., the moving limb) binocular cues serve to specifically optimize online reaching control. Moreover, results provide new evidence that differences in the kinematic and endpoint parameters of binocular and monocular reaches reflect differences in the extent to which the aforementioned engage in online and offline modes of movement control.

Differences in temporal frequency tuning between the two binocular mechanisms for seeing motion in depth

There are two types of binocular cues available for perception of motion in depth. One is the binocular disparity change in time and the other is the velocity difference between the left and the right retinal images (inter-ocular velocity differences). We measured the luminance contrast threshold for seeing motion in depth while isolating either of the cues at various temporal modulations of velocity in the stimulus. To isolate disparity cues, dynamic random-dot stereograms were used (the disparity condition) while binocularly uncorrelated random-dot kinematograms were used to isolate velocity cues (the velocity condition). Results showed that sensitivity peaked at a temporal frequency (approximately 1 cps) in the velocity condition while the peak in the disparity condition was at the lowest frequency (0.35 cps) or at least at a frequency lower than that in the velocity condition. This suggests that the visual system has different temporal frequency properties for the velocity and disparity cues for motion in depth.

Strong percepts of motion through depth without strong percepts of position in depth

Encoding the motion of objects through three spatial dimensions is a fundamental challenge for the visual system. Two binocular cues could contribute to the perception of motion through depth: changes in horizontal disparity (CD) and interocular velocity differences (IOVD). Although conceptually distinct, both cues are typically present when real objects move. Direct experimental isolation of the putative IOVD cue has remained elusive, and it is therefore unclear to what extent the visual system relies on it. We have found that binocularly anticorrelated stimuli impair position in depth judgments, but motion through depth judgments for the same stimuli are relatively unaffected. This dissociation of direction of motion from position in depth provides strong evidence that percepts of motion through depth are not based exclusively on estimating changes in disparity. Horizontal IOVDs appear to complement the CD cue. Vertical IOVDs fail to yield comparable performance, further implicating a comparison of horizontal interocular velocity and also ruling out explanations of our results based on monocular cues. These results suggest that (1) IOVDs are a robust cue to motion through depth; (2) IOVDs and retinal disparities exhibit similar horizontal/vertical anisotropies, consistent with the geometry of binocular viewing; and (3) binocular anticorrelation provides means to titrate the relative contributions of CD and IOVD cues.

Matching boxes: Familiar size influences action programming

The perception/action model is the dominant account of the primary division of labour in the human visual pathway. Integral to this model is the idea that goal-directed actions are guided spatially by bottom-up vision, independent of perceptual recognition and top-down object knowledge. We question this idea by showing that the expected size of familiar objects (matchboxes) affects the amplitude of reaches made to grasp them, and the pre-shaping of the hand, even when binocular cues are available. This suggests that perceptual recognition routinely influences action programming.

Isthmotectal axons maintain normal arbor size but fail to support normal branch numbers in dark‐reared Xenopus laevis

Developing binocular projections to the Xenopus tectum require visual input in order to establish matching topographic maps. In dark-reared Xenopus, the ipsilateral eye's map, relayed via the retino-tecto-isthmotectal pathway, fails initially to acquire normal rostrocaudal order. Moreover, with extended time in the dark, the ipsilateral map becomes progressively less well organized. This phenomenon showed that without binocular cues, the isthmotectal axons are unable to locate proper sites for their terminal zones but left open the issue of whether the axons are able to establish arbors of normal dimensions and/or to sustain normal numbers of branches. In order to test whether dark-rearing modifies isthmotectal axon branching, we have used horseradish peroxidase to examine axons of Xenopus after dark-rearing for periods from 3 to 298 weeks. The results demonstrate that these axons never acquire more than about half the normal numbers of terminals. Surprisingly, however, the dark-reared axons' terminal zones are normal in mediolateral and rostrocaudal extent despite the lack of binocular cues that normally could constrain arbor size by inducing pruning of branches in regions with mismatched visual inputs. The effects of dark-rearing are reversible. After a return to normal lighting conditions, the recovery process begins quickly, with a significant increase in branch numbers within 4 weeks. The terminal zone remains of normal dimensions. These results support the hypothesis that correlated binocular visual input is essential for the maintenance of normal numbers of isthmotectal branches but that normal termination zone size can be established in the absence of visual cues.

Highlight disparity contributes to the authenticity and strength of perceived glossiness

The disparity of highlights on specular reflecting surfaces usually differs from the disparity of the surface points. A. Kirschmann (1895) proposed that this fact may be used as a binocular cue for gloss perception. This was confirmed by A. Blake and H. Bülthoff (1990) who found that subjects judged the glossiness of convex ellipsoidal surfaces as most realistic if the disparity of the highlights was close to the physical correct one. Extending on this finding, we investigate more closely whether the effect of highlight disparity depends on the sharpness of the highlight and the relative amount of diffuse and specular reflection. We measured the effect of highlight disparity on both perceived strength and perceived authenticity of gloss. We used complex, three-dimensional curved surfaces that were stereoscopically presented on a CRT. The reflection characteristics were varied using the Phong lighting model. Highlights were presented either with or without highlight disparity. In a rating experiment, subjects were asked to judge the strength and the authenticity of the perceived surface glossiness. The presence of highlight disparity lead to an enhancement of both the authenticity and the strength of perceived glossiness. The latter finding was confirmed in an additional matching experiment.

Binocular vision and motion-in-depth

When an object moves in three dimensions, the two eyes' views of the world deliver slightly different information to the visual system, providing binocular cues to depth and motion-in-depth. This short review describes the two main sources of binocular information, namely, changing disparity over time and interocular velocity differences; this could be used for the perception of motion-in-depth. We discuss the evidence obtained in recent years on the extent to which each of them is used in human vision. We also highlight outstanding questions and issues in the field that have yet to be addressed.

Judging surface slant for placing objects: a role for motion parallax

People have a variety of sources of information (cues) about surface slant at their disposal. We used a simple placing task to evaluate the relative importance of three such cues (motion parallax, binocular disparity and texture) within the space in which people normally manipulate objects. To do so, we projected a stimulus onto a rotatable screen. This allowed us to manipulate texture cues independently of binocular disparity and motion parallax. We asked people to stand in front of the screen and place a cylinder on the screen. We analysed the cylinder’s orientation just before contact. Participants mainly relied on binocular cues (weight between 50 and 90%), in accordance with binocular cues being known to be reliable when the stimulus surface is nearby and almost frontal. Texture cues contributed between 2 and 18% to the estimated slant. Motion parallax was given a weight between 1 and 9%, despite the fact that it only provided information when the head began to move, which was just before the arm did. Thus motion parallax is used to judge surface slant, even when one is under the impression of standing still.

Temporal aspects of cue combination

The human brain processes different kinds of information (or cues) independently with different neural latencies. How does the brain deal with these differences in neural latency when it combines cues into one estimate? To find out, we introduced artificial asynchronies between the moments that monocular and binocular cues indicated that the slant of a surface had suddenly changed. Subjects had to detect changes in slant or to indicate their direction. We found that the cues were combined to improve performance even when the artificial asynchrony between them was about 100 ms. We conclude that neural latency differences of tens of milliseconds between cues are irrelevant because of the low temporal resolution of neural processing.

Poster 28: Vocational Rehabilitation for a Nurse With Stargardt’s Disease

Accommodation, or the change in refractive power of the eye to focus objects at different distances, is driven by many stimuli including defocus blur, the awareness of target distance or proximal cues, and through the vergence crosslink (convergence acccommodation). The effectiveness of defocus blur as an accommodative stimulus is decreased in normally-sighted subjects as visual acuity is experimentally reduced and as the target is imaged at increasing eccentricities from the fovea. Since subjects with central retinal abnormalities have reduced visual acuity and typically fixate eccentrically, one would predict that defocus blur would not be an effective accommodative stimulus for them. Using an infrared optometer, steady-state accommodative responses of six subjects with juvenile macular degeneration (JMD) and of three normally-sighted controls were measured. The effectiveness of defocus blur in stimulating accommodation varied across the subjects and was related to visual acuity, with those subjects having worse acuity showing less accurate accommodative responses. When provided with additional cues to accommodative demand (i.e. proximal and/or binocular cues), subjects with JMD showed more accurate accommodative responses. In general, those subjects who did not modulate accommodative response with changing defocus blur cues showed the most accurate accommodation under binocular viewing. In contrast, those subjects who did change accommodative response with changing defocus blur cues showed the most accurate accommodation under monocular viewing.

Spatial scale of stereomotion speed processing

To examine the spatial scale of the mechanisms supporting the perception of motion in depth defined by binocular cues, we measured stereomotion speed discrimination thresholds as a function of stimulus size using a two-interval speed comparison task. Stimuli were either random dot stereogram (RDS) bars featuring both the changing disparity (CD) and the interocular velocity difference (IOVD) cues to motion in depth or dynamic random dot stereogram (DRDS) bars featuring the CD cue alone. Monocular speed discrimination performance was also assessed, using half-images of the RDS stimulus. In addition, subjects' stereoacuity for stationary versions of the binocular stimuli was measured. Stimuli ranged in vertical extent from 1.25 to 40 min. Sensitivity to speed differences was strongly related to stimulus height for DRDS stimuli. Performance decreased rapidly as stimulus size was reduced, becoming nearly random for heights below 5 min. However, for RDS stimuli, speed discrimination performance declined with reductions in stimulus size at a far slower rate, providing superior performance at every stimulus size used. Monocular performance was superior still for the majority of subjects, yet showed a similar rate of decline to binocular RDS stimuli. We conclude that the spatial resolution of the CD mechanism and its static disparity inputs is, on average, nearly nine times more coarse than the IOVD system and its monocular motion inputs. Static stereoacuity controls show that this finding cannot be explained by differences in the disparity signals available in our RDS and DRDS stimuli.

An ROV Stereovision System for Ship-Hull Inspection

Ship hulls, as well as bridges, port dock pilings, dams, and various underwater structures need to be inspected for periodic maintenance. Additionally, there is a critical need to provide protection against sabotage activities, and to establish effective countermeasures against illegal smuggling activities. Unmanned underwater vehicles are suitable platforms for the development of automated inspection systems, but require integration with appropriate sensor technologies. This paper describes a vision system for automated ship-hull inspection, based on computing the necessary information for positioning, navigation, and mapping of the hull from stereo images. Binocular cues are critical in resolving a number of complex visual artifacts that hamper monocular vision in shallow-water conditions. Furthermore, they simplify the estimation of vehicle pose and motion, which is fundamental for successful automatic operation. The system has been implemented on a commercial remotely operated vehicle (ROV), and tested in pool and dock tests. Results from various trials are presented to demonstrate the system capabilities

An Evaluation of the Agreement Between Contour-Based Circles and Random Dot-Based Near Stereoacuity Tests

Monocular cues are present in the contour-based Titmus and Randot circles stereoacuity tests frequently giving rise to false-positive results in patients with abnormal stereoacuity. Stereoacuity derived using these 2 test types was compared to evaluate whether discrepancies between these tests were limited to the coarse/nil end of the stereoacuity spectrum or whether they were apparent across a wider range of possible stereoacuity scores, including levels of stereopsis equated with macular fusion. Fifty-four normal volunteers and 91 patients with a history of anomalous binocular vision by a variety of conditions (eg, strabismus, monovision, or unilateral eye disease) participated. In each participant, stereoacuity was measured using the Titmus(c) circles, the Randot(c) (version 2) circles, and the Preschool Randot(c) Stereoacuity test. In patients with a history of anomalous binocular vision, better stereoacuity scores were acquired using the circles tests than the random dot-based Preschool Randot Stereoacuity test (Friedman repeated-measures analysis of variance on ranks, Chi-square = 99.3, P < 0.001; Student-Newman-Keuls Method, P < 0.05). Among patients with known binocular vision anomalies, stereoacuity score disagreement was evident across the entire range of measurable stereoacuity. Stereoacuity score discrepancies between the circles tests and the random dot based tests frequently cross categories (eg, fine vs. moderate or coarse stereopsis). Disagreement between the test types may reflect different underlying mechanisms by the different types of tests or confounding nonstereoscopic binocular cues in the Titmus and Randot circles test.

Aftereffects of motion in depth based on binocular cues

Aftereffects of motion in depth based on binocular cues

Vision for robotic object manipulation in domestic settings

In this paper, we present a vision system for robotic object manipulation tasks in natural, domestic environments. Given complex fetch-and-carry robot tasks, the issues related to the whole detect-approach-grasp loop are considered. Our vision system integrates a number of algorithms using monocular and binocular cues to achieve robustness in realistic settings. The cues are considered and used in connection to both foveal and peripheral vision to provide depth information, segmentation of the object(s) of interest, object recognition, tracking and pose estimation. One important property of the system is that the step from object recognition to pose estimation is completely automatic combining both appearance and geometric models. Experimental evaluation is performed in a realistic indoor environment with occlusions, clutter, changing lighting and background conditions.

The role of (micro)saccades and blinks in perceptual bi-stability from slant rivalry

We exposed the visual system to an ambiguous 3D slant rivalry stimulus consisting of a grid for which monocular (perspective) and binocular (disparity) cues independently specified a slant about a horizontal axis. When those cues specified similar slants, observers perceived a single slant. When the difference between the specified slants was large, observers alternatively perceived a perspective- or a disparity-dominated slant. Eye movement measurements revealed that there was no positive correlation between a perceptual flip and both saccades (microsaccades as well as larger saccades) and blinks that occurred prior to a perceptual flip. We also found that changes in horizontal vergence were not responsible for perceptual flips. Thus, eye movements were not essential to flip from one percept to the other. After the moment of a perceptual flip the occurrence probabilities of both saccades and blinks were reduced. The reduced probability of saccades mainly occurred for larger voluntary saccades, rather than for involuntary microsaccades. We suggest that the reduced probability of voluntary saccades reflects a reset of saccade planning.

Integrating visual cues for motor control: A matter of time

The visual system continuously integrates multiple sensory cues to help plan and control everyday motor tasks. We quantified how subjects integrated monocular cues (contour and texture) and binocular cues (disparity and vergence) about 3D surface orientation throughout an object placement task and found that binocular cues contributed more to online control than planning. A temporal analysis of corrective responses to stimulus perturbations revealed that the visuomotor system processes binocular cues faster than monocular cues. This suggests that binocular cues dominated online control because they were available sooner, thus affecting a larger proportion of the movement. This was consistent with our finding that the relative influence of binocular information was higher for short-duration movements than long-duration movements. A motor control model that optimally integrates cues with different delays accounts for our findings and shows that cue integration for motor control depends in part on the time course of cue processing.