SEARCH · Search PubMed

Results for “Depth Perception”

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.

SourceResearch connectionFrom yearThrough year

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

At least 595 records · Page 33Linked to original sources

PubMed1991

On the coexistence of stereopsis and binocular rivalry.

Dichoptically viewed complex texture stereograms with correlated spatial frequency information can yield stable depth perception, implying cooperative interaction between the two eyes. Dichoptically viewed dissimilar texture pairs may yield competition in the form of binocular rivalry. To study whether stereopsis and rivalry can spatially coexist when stimulus conditions for both are present, we had observers dichoptically view spatial frequency filtered random-dot patterns. The left eye viewed one half-image of an RDS; the right eye viewed the superimposition of the other RDS half-image (which when paired alone with the left-eye RDS yielded stereoscopic depth) and a noise target (which on its own engaged in rivalry with the right eye target). Observers judged the quality of depth and the rate of rivalry for these stereo-pairs. When the contrast of the noise component was low, observers experienced stereopsis and stable single vision that included the noise. At intermediate noise contrasts, local regions were seen either in rivalry or in stereoscopic depth, but rivalry and depth were not experienced at the same spatial location simultaneously. At high noise contrasts, the right eye target dominated almost exclusively, with little hint of stereopsis. Essentially the same pattern of results was obtained in forced-choice experiments in which observers judged the direction of stereoscopic tilt from vertical cosine gratings differing slightly in spatial frequency. Considered together, these results are inconsistent with theories positing that rivalry and stereopsis coexist at the same spatial location because they occur within independent, parallel pathways.

Depth Perception↗

PubMed1992

Common region: a new principle of perceptual grouping.

A new principle of grouping is proposed that is based on elements being located within a common region of space. Demonstrations analogous to Wertheimer's original displays show that this factor strongly influences perceived grouping and is capable of overcoming the effects of other powerful grouping factors such as proximity and similarity. Grouping by common region is further shown to depend on perceived depth relations, indicating that it is influenced by processes that occur after at least some depth perception has been achieved. Further demonstrations suggest that it is dominated by the smallest background area and that it can follow a hierarchical embedding scheme. It is argued that common region cannot be reduced to the effects of proximity, closure, or any other previously known factor and therefore constitutes a genuinely new principle of grouping.

Depth Perception↗

PubMed2001

Monovision: a review of the scientific literature.

We reviewed the scientific literature on monovision to compare the visual performance of monovision patients with that of others wearing more traditional prescriptions. We found that visual performance of monovision patients was comparable to that of control patients wearing a balanced binocular correction, provided that reading adds were not greater than about +2.5 D, that illumination was photopic, and that stimuli were presented at supra-threshold levels. Under these conditions, monovision patients were satisfied with their perceptual experience and performed within 2 to 6% of balanced binocular control patients on a range of occupational tasks. It is noteworthy that monovision patients had relatively more difficulty with acuity-based tasks than with tasks demanding good depth perception. With reading adds over +2.5 D, at low levels of illumination, or with near-threshold level stimuli, visual performance of monovision patients was reduced compared with controls. Subjectively, under low levels of illumination, monovision patients experienced problems with glare and halos around point sources of light.

Contact Lenses↗

PubMed2000

Horizontal-disparity tuning of neurons in the visual forebrain of the behaving barn owl.

Stereovision plays a major role in depth perception of animals having frontally-oriented eyes, most notably primates, cats, and owls. Neuronal mechanisms of disparity sensitivity have only been investigated in anesthetized owls so far. In the current study, responses of 160 visual Wulst neurons to static random-dot stereograms (RDS) were recorded via radiotelemetry in awake, fixating barn owls. The majority of neurons (76%) discharged significantly as a function of horizontal disparity in RDS. The distribution of preferred disparities mirrored the behaviorally relevant range of horizontal disparities that owls can exploit for depth vision. Most tuning profiles displayed periodic modulation and could well be fitted with a Gabor function as expected if disparity detectors were implemented according to the disparity energy model. Corresponding to this observation, a continuum of tuning profiles was observed rather than discrete categories. To assess a possible clustering of neurons with similar disparity-tuning properties, single units, and multi-unit activity recorded at individual recording sites were compared. Only a minority of neurons were clustered according to their disparity-tuning properties, suggesting that neurons in the visual Wulst are not organized into columns by preferred disparity. To assess whether variable vergence eye movements influenced tuning data, we correlated tuning peak positions on a trial-by-trial basis for units that were recorded simultaneously. The general lack of significant correlation between single-trial peak positions of simultaneously recorded units indicated that vergence, if at all, had only a minor influence on the data. Our study emphasizes the significance of visual Wulst neurons in analyzing stereoscopic depth information and introduces the barn owl as a second model system to study stereopsis in awake, behaving animals.

Action Potentials↗

PubMed1998

Spatial perception in macroscopic and microscopic surgical manipulations: differences between experienced and inexperienced surgeons.

The spatial perceptions of the phantom surgical field with the naked eye and under the surgical microscope were analyzed in a group of experienced and a group of inexperienced neurosurgeons. The phantom surgical field contained a start point, a virtual gate, and a target point. The virtual gate was an invisible zone arbitrarily set in the phantom surgical field. The examinees were first instructed regarding the position of the invisible virtual gate. Then they were asked to point consecutively to the three points with a suction tube under three different circumstances: with the naked eye, under the microscope, and by watching a navigation monitor. A surgical navigator was used to record the three-dimensional position of the suction tip. The pointing deviation from the suction tip to the center of the virtual gate was evaluated. The pointing accuracy with the naked eye did not differ between the two groups, but that under the microscope was significantly better in the experienced group than in the inexperienced group. Fluctuations in pointing deviation were significantly greater in the inexperienced neurosurgeons, especially with the microscope. Further analysis demonstrated that these differences were attributable to poorer depth perception of the phantom surgical space among the inexperienced neurosurgeons.

Clinical Competence↗

PubMed2005

Motion parallax driven by head movements: conditions for visual stability, perceived depth, and perceived concomitant motion.

Yoking the movement of the stimulus on the screen to the movement of the head, we examined visual stability and depth perception as a function of head-movement velocity and parallax. In experiment 1, for different head velocities, observers adjusted the parallax to find (a) the depth threshold and (b) the concomitant-motion threshold. Between these thresholds, depth was seen with no perceived motion. In experiment 2, for different head velocities, observers adjusted the parallax to produce the same perceived depth. A slower head movement required a greater parallax to produce the same perceived depth as faster head movements. In experiment 3, observers reported the perceived depth for different parallax magnitudes. Perceived depth covaried with smaller parallax without motion perception, but began to decrease with larger parallax and concomitant motion was seen. Only motion was seen with the larger parallax.

Adult↗

PubMed2000

Unconstrained stereoscopic matching of lines.

The computation of horizontal binocular disparities used in stereoscopic depth perception depends upon the identification of corresponding features in the two retinal images. In principle, binocular matching is a two-dimensional problem that considers matches in all possible meridians. Normally, constraints such as end points or crossing points limit the direction and magnitude of matches. If matching is unconstrained, such as is the case with long lines, it is completely ambiguous. Under these conditions the default match will be determined by the operating range, or upper disparity limit, of matchable vertical and horizontal disparities. We computed the operating range of vertical matches for stereoscopic depth as a function of line orientation. Our results suggest that the two-dimensional operating range is anisotropic for vertical and horizontal disparity and that unconstrained matches are not based upon either epipolar geometry or nearest neighbor constraints, but rather the mean of disparity estimates within the operating range for binocular matches. This operating range can be extended vertically when matches are constrained by image primitives.

Depth Perception↗

PubMed1999

Characteristics of accommodation toward apparent depth.

This paper deals with characteristics of accommodation evoked by perceived depth sensation and the dynamic relationship between accommodation and vergence, applying newly developed optical measurement apparatuses. A total of five subjects looked at three different two-dimensional stimuli and two different three-dimensional stimuli; namely a real image and a stereoscopic image. With regard to the two-dimensional stimuli, a manifest accommodation without any accompanying vergence was found because of an apparent depth sensation even though the target distance was kept constant. With regard to the three-dimensional stimuli, larger accommodation and clear vergence were evoked because of binocular parallax and a stronger depth sensation. As for the stereoscopic image, a manifest overshoot (the accommodation peaked first and receded considerably) was found while the vergence remained constant. On the other hand, the overshoot of accommodation was smaller when subjects were watching the real image. These results reveal that brain depth perception has a higher effect on accommodation than expected. The relationship of accommodation and vergence toward the stereoscopic image suggests a reason why severe visual fatigue is commonly experienced by many viewers using stereoscopic displays. It has also paved the way for the numerical analysis of the oculomotor triad system.

Accommodation, Ocular↗

PubMed2000

Body sway induced by depth linear vection in reference to central and peripheral visual field.

PURPOSE: A significant correlation between the magnitude of linear vection and the degree of body sway induced by a visual stimulus perceived as moving in depth was previously described (Jpn J Physiol 49: 417-424, 1999). The purpose of this study was to examine the role of the central and peripheral visual fields in inducing vection and body sway. METHODS: Ten healthy volunteer students who had no vestibular or neurological disorders served as subjects. A depth optokinetic stimulus (DOKS) was projected onto a head-mounted display (HMD) and was perceived to move in depth. Different amounts of the central or peripheral visual field were masked independently. The magnitude of the linear vection induced by the DOKS was evaluated by verbal assessment and compared with the magnitude of induced body sway. Body sway was monitored by a video-motion-analyzer that recorded the movement of the head, shoulder, hip, knee and ankle. RESULTS: The magnitude of vection was correlated with the frequency of DOKS and also with the amplitude of body sway (r = 0.74). When the central visual field was restricted by 10 to 30%, there was almost no change in the induced body sway and vection. However, when central occlusion was greater than 40%, depth perception and induced body movement were greatly reduced. With increasing amounts of peripheral field occlusion from 50 to 90%, there was a greater reduction of both vection and body sway. CONCLUSION: Vection is strongly correlated with body movement, and vection and body sway were more dependent on stimulation of the peripheral visual field.

Adult↗

PubMed1993

Visual learning in the hyperacuity range in adults.

We investigated the amount, speed, and specificity of the learning of new visual tasks in adult humans using stereoscopic depth perception and vernier discrimination as the sensitive probes for learning. The results of psychophysical experiments in untrained adult observers indicate two phases of highly specific perceptual learning in humans: a fast phase and a slower one. Both types of learning might take place relatively "early" during pattern recognition in the visual cortex, since learning was very specific, without transfer between different stimulus orientations.

Depth Perception↗

PubMed1998

[Higher cortical dysfunctions in preterm diplegia: how to evaluate and treat for their pedagogical difficulties].

Preterm diplegic children (SD) frequently suffer pedagogical difficulties. They showed visual perceptual impairments and also constructional dyspraxia, neuropsychologically. Multiple regression analysis proved that the constructional dyspraxia was independent from the impairments of visual acuity, stereoacuity, depth perception and visual perception. EEG coherence analysis in SD patients disclosed lower interhemispheric coherence at alpha band frequency in occipital derivations. The lower coherence value may correspond to thinning of posterior body and splenium of corpus callosum in SD patients. A adequate ophthalmological treatments, books with enough space between the lines and three dimensional models to facilitate the image of stereography are recommended.

Audiovisual Aids↗

PubMed1985

Stereoscopic stimuli activate different cortical neurones in man: electrophysiological evidence.

Dynamic random dot stimuli offer the possibility to study cortical neuronal mechanisms related to depth perception in man because these stimuli operationally skip all stages prior to the activation of cortical binocular disparity neurones. In the present paper, the scalp topography of brain potential components evoked by stereoscopic stimuli are compared with those evoked by similar binocular contrast stimuli, and our results present evidence that different neuronal populations of the visual cortex are activated in these two stimulus conditions.

Adult↗

PubMed1980

Stereopsis in human infants.

Stereoscopic depth perception was tested in human infants by a new method based on attracting the infant's attention through movement of a stereoscopic contour formed from a dynamic random-element stereogram. The results reveal that stereopsis emerges at 3 1/2 to 6 months of age, an outcome consistent with evidence for rapid postnatal development of the visual system.

Age Factors↗

PubMedDate not supplied

Bile duct injuries in the era of laparoscopic cholecystectomy.

By the introduction of laparoscopic cholecystectomy a new field of surgical development has been opened, resulting in the reduction of conventional surgical trauma, and giving the chance to the patient seeking for less postoperative pain, short hospital stay and quick return to activity and work. In spite of these advantages, many laparoscopic cholecystectomy related complications occurred, especially in the period of the learning curve. Due to the special technical requirements, problems of the two dimensional vision, depth perception and hand-eye coordination guided to injuries of the bile ducts, which reached a high rate of 3%. This rate is ten times more when compared with conventional cholecystectomy. The authors present a detailed account of the causes of the injuries, their typical localisation and the best way to avoid and treat them.

Activities of Daily Living↗

PubMed1989

Fundamentals of stereophotography in medicine.

Depth perception is given by binocular vision and it can be reproduced photographically by taking left and right pictures. However, the optimum separation between the views may not always correspond to the distance between our eyes, particularly in close-up work. Important applications of stereophotography in medicine are examined in this article as well as some of the fundamental principles and techniques for taking 3-D pictures and viewing the results.

Depth Perception↗

PubMed1997

Binocular matching of dissimilar features in phantom stereopsis.

Previously we have demonstrated that quantitative depth perception can be elicited from a stereogram that lacks contrast defined binocular corresponding elements (phantom stereopsis). In this report, we use computer simulation to demonstrate that it is biologically plausible for some known binocular cortical cell types to combine non-conventional matching features. Therefore, binocular matching processes based on the responses of these cells could be a conventional one, namely, looking for similar response patterns in the two eyes. While at cell types we simulated gave identical disparity outputs to the conventional stereogram, they responded differently to the phantom stereogram. Processes other than low-level disparity detectors may have to be invoked in order to achieve a unique depth solution.

Computer Simulation↗

PubMed2003

When does grouping happen?

Recent research on perceptual grouping is described with particular emphasis on identifying the level(s) at which grouping factors operate. Contrary to the classical view of grouping as an early, two-dimensional, image-based process, recent experimental results show that it is strongly influenced by phenomena related to perceptual constancy, such as binocular depth perception, lightness constancy, amodal completion, and illusory contours. These findings imply that at least some grouping processes operate at the level of phenomenal perception rather than at the level of the retinal image. Preliminary evidence is reported showing that grouping can affect perceptual constancy, suggesting that grouping processes must also operate at an early, preconstancy level. If so, grouping may be a ubiquitous, ongoing aspect of visual organization that occurs for each level of representation rather than as a single stage that can be definitively localized relative to other perceptual processes.

Depth Perception↗

PubMed1996

Cortical visual dysfunction in children: a clinical study.

Damage to the cerebral cortex was responsible for impairment in vision in 90 of 130 consecutive children referred to the Vision Assessment Clinic in Glasgow. Cortical blindness was seen in 16 children. Only 2 were mobile, but both showed evidence of navigational blind-sight. Cortical visual impairment, in which it was possible to estimate visual acuity but generalised severe brain damage precluded estimation of cognitive visual function, was observed in 9 children. Complex disorders of cognitive vision were seen in 20 children. These could be divided into five categories and involved impairment of: (1) recognition, (2) orientation, (3) depth perception, (4) perception of movement and (5) simultaneous perception. These disorders were observed in a variety of combinations. The remaining children showed evidence of reduced visual acuity and/ or visual field loss, but without detectable disorders of congnitive visual function. Early recognition of disorders of cognitive vision is required if active training and remediation are to be implemented.

Adolescent↗