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PubMed1989

Amphetamine-induced recovery of visual cliff performance after bilateral visual cortex ablation in cats: measurements of depth perception thresholds.

After bilateral visual cortex ablation, cats exhibit a loss of depth perception as measured on a visual cliff, which recovers following administration of d-amphetamine. In this Study, 3 amphetamine-treated cats with visual cortex ablations showed a rapid and enduring recovery, with 2 of these animals obtaining levels of performance seen only with binocular vision, suggesting a restoration of binocular depth perception. Cats with asymmetrical lesions showed only a transient improvement during amphetamine treatment, and some animals not displaying autonomic signs of amphetamine intoxication did not improve. Saline-treated cats showed no signs of improvement, and the effect of amphetamine was blocked by the catecholaminergic antagonist haloperidol. These results indicate that amphetamine can induce an enduring recovery from a behavioral deficit after brain injury, which if left untreated would not spontaneously recover.

Amphetamine↗
PubMed2006

Does depth perception require vertical-disparity detectors?

Stereo depth perception depends on the fact that objects project to different positions in the two eyes. Because our eyes are offset horizontally, these retinal disparities are mainly horizontal, and horizontal disparity suffices to give an impression of depth. However, depending on eye position, there may also be small vertical disparities. These are significant because, given both vertical and horizontal disparities, the brain can deduce eye position from purely retinal information and, hence, derive the position of objects in space. However, we show here that, to achieve this, the brain need measure only the magnitude of vertical disparity; for physically possible stimuli, the sign then follows from the stereo geometry. The magnitude of vertical disparity--and hence eye position--can be deduced from the response of purely horizontal-disparity sensors because vertical disparity moves corresponding features off the receptive fields, reducing the effective binocular correlation. As proof, we demonstrate an algorithm that can accurately reconstruct gaze and vergence angles from the population activity of pure horizontal-disparity sensors and show that it is subject to the induced effect. Given that disparities experienced during natural viewing are overwhelmingly horizontal and that eye position measures require only horizontal-disparity sensors, this work raises two questions: Does the brain in fact contain sensors tuned to nonzero vertical disparities, and if so, why?

Algorithms↗
PubMed2005

Ordinal configural cues combine with metric disparity in depth perception.

Prior research on the combination of depth cues generally assumes that different cues must be in the same units for meaningful combination to occur. We investigated whether the geometrically ordinal cues of familiarity and convexity influence depth perception when unambiguous metric information is provided by binocular disparity. We used bipartite, random dot stereograms with a central luminance edge shaped like a face in profile. Disparity specified that the edge and dots on one side were closer than the dots on the other side. Configural cues suggested that the familiar, face-shaped region was closer than the unfamiliar side. Configural cues caused an increase in perceived depth for a given disparity signal when they were consistent with disparity and a decrease in perceived depth when they were inconsistent. Thus, geometrically ordinal configural cues can quantitatively influence a metric depth cue. Implications for the combination of configural and depth cues are discussed.

Cues↗
PubMed1989

Binocular depth perception, visual acuity and visual fields in cats following neonatal section of the optic chiasm.

We studied the role of the transcallosal pathway in stereopsis by measuring binocular and monocular depth perception in two cats that had undergone section of the optic chiasm at the age of 21 d. To ensure that the surgery did not impair vision to the extent that depth perception could not be evaluated, visual acuity and visual fields were also measured. In both of the chiasm-sectioned animals the visual fields were reduced and the visual acuity was substantially lower than in normal cats, with a maximum of about 2 cyc deg-1. Binocular depth thresholds of the chiasm-sectioned cats were worse than those of the normal cat but were better than their own monocular thresholds. These results suggest that the chiasm-sectioned animals were still able to use binocular cues to judge depth and indicate that the indirect pathway through the corpus callosum is sufficient to mediate binocular depth perception.

Depth Perception↗
PubMed1985

Binocular depth perception in the cat following early corpus callosum section.

The role of the corpus callosum in the mediation of binocular depth perception was examined by measuring monocular and binocular depth discrimination thresholds in cats which had undergone section of the corpus callosum shortly after birth. Three kittens had the posterior callosum sectioned at the age of eleven days. A fourth kitten underwent a sham operation and one additional animal served initially as an unoperated control. Monocular and binocular depth thresholds were measured for all kittens when they were between three and five months old. Although there was some individual variability, none of the callosum-sectioned kittens showed any deficits of binocular depth perception relative to normal animals. The initially unoperated kitten had its callosum sectioned at five months and was retested following surgery. Its performance did not change from preoperated levels. Finally, the three neonatal callosum-sectioned kittens underwent section of the optic chiasm when they were six months old, causing a complete breakdown in binocular depth discrimination. The results are interpreted to indicate that although the corpus callosum may be a sufficient pathway for the maintenance of stereopsis in cat, it is not necessary.

Animals↗
PubMed2001

[The Titmus Fly Test--evaluation of subjective depth perception with a simple finger pointing trial. Clinical study of 73 patients and probands].

BACKGROUND: Subjects with different binocular defects were tested for their stereoscopic achievement. The determination of the subjects limiting disparity (in seconds of arc) was not used to characterize their stereoscopic acuity, but the subjective depth perception as a simple clinical method. METHODS: 52 subjects with different binocular defects and 21 normosensoric volunteers were examined for their stereoscopic achievement. In our stereoscopic measurement we ask the subjects to indicate the subjective plane of the fly's wings manually by their own finger, or by a hand-held plastic card, or with the aid of a mechanic instrument. The results of the different methods were compared with each other. RESULTS: There were no differences between the results within the group of normosensoric subjects. The patients with reduced abilities exhibit significantly different results in depth perception when measured manually or by machinery. The subjective depth localization correlates well with the binocular defect and is independent of the used stereoscopic method. CONCLUSIONS: The basic finger test of the subjective level of the Fly's wings gives a quite reasonable approximation of local stereoscopic depth perception. In terms of practical investigation the finger test shows in convincing manner whether the individual stereoscopic ability is based on normal, subnormal or anomalous binocular interaction.

Adolescent↗
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↗
PubMed1991

Influence of remote objects on local depth perception.

The perceived relative depth of two test dots displayed within the fovea is shown to be influenced by other features in the surrounding area. These features can be as far apart as 51 deg and can have relative disparities as large as 20 deg, much larger than the disparities of the test dots. Since this effect is seen for stimuli presented for 100 msec or less, changes in direction of gaze cannot play a role. The effect varies inversely as the spatial separation between the test dots and the remote features, and is insensitive to the relative disparities of these remote features when they are greater than 2 deg. Observers sometimes differ significantly from each other in their responses to various configurations of the outlying features. This appears to rule out response mechanisms which depend only on the stimulus; some characteristics of the observer must be involved in determining the response. For these briefly presented stimuli, observers are unable to report accurately the relative depth of the central foveated test items if they are also required to report the depths of distant peripheral features.

Depth Perception↗
PubMed1992

Shape analysis and stereopsis for human depth perception.

The perceived relative depth of two isolated short parallel lines in the center of a scene is known to depend on the disparities and positions of other items in the scene, as well as on their own disparities. We demonstrate here that the shapes of these other items also contribute significantly to the perceived depth, and that these non-disparity influences on depth judgements may already be evident when only three dots are presented as stimuli. When two short vertical test lines are surrounded by a trapezoidal "picture frame", the perceived relative depth of the test lines is affected by the shape of the trapezoid as well as by the disparities assigned to its vertical parallel sides. The influence of the trapezoidal frame can be interpreted as an effect of perspective. The induced relative depth of the test lines is measured by recording the amount of "compensating disparity" that must be given to one of the lines in order for observers to judge the two test lines to be equidistant from the observer's viewing position. Surprisingly, for fixed disparities of the vertical edges of the surrounding picture frame, the induced depth of the test lines increases as the difference in the lengths of the vertical sides increases, regardless of whether the perspective interpretation of the difference in the lengths is consistent with or in conflict with the disparity-defined slant. Shape-related apparent depth changes are especially sensitive to the shape of the trapezoid if it is nearly rectangular, and are comparable in magnitude to those resulting from changes in disparity of the surrounding frame. When a pair of short vertical parallel test lines is presented alone, without a surrounding frame or any other items in the scene, excellent relative depth discrimination is displayed by most subjects. However, if the lines are replaced by squares, trapezoids, triangles, single horizontal lines, or other figures of about the same size as the original test lines, the slant discrimination threshold for these plane figures for naïve observers become poorer by a factor of 20-100. By the use of a feedback signal, observers can be trained to use only disparity cues and ignore shape effects. Some observers have difficulty ignoring the shapes of some figures, the "difficult" figures being different for each observer. After training, the relative depth thresholds for most figures approach those of the original unconnected parallel test lines.

Depth Perception↗
PubMedDate not supplied

Enhancing depth perception in translucent volumes.

We present empirical studies that consider the effects of stereopsis and simulated aerial perspective on depth perception in translucent volumes. We consider a purely absorptive lighting model, in which light is not scattered or reflected, but is simply absorbed as it passes through the volume. A purely absorptive lighting model is used, for example, when rendering digitally reconstructed radiographs (DRRs), which are synthetic X-ray images reconstructed from CT volumes. Surgeons make use of DRRs in planning and performing operations, so an improvement of depth perception in DRRs may help diagnosis and surgical planning.

Algorithms↗
PubMed1999

Listing's plane rotation with convergence: role of disparity, accommodation, and depth perception.

Earlier studies have reported temporal rotation of Listing's plane with convergence of the eyes causing torsion, which is dependent on eye elevation. The amount by which the planes rotate differs from study to study. To gain insight into the functional significance of the temporal tilt of Listing's plane for vision, we examined whether the rotation of the plane depends on the visual conditions, namely on the stimuli driving vergence. In different conditions, accommodative vergence, disparity-vergence, combinations of disparity with accommodation or depth perception were used and the resulting rotation of Listing's plane was measured. Our findings show, for the first time, that the relationship between convergence and Listing's-plane temporal rotation depends on the stimuli driving vergence. When the stimulus contains only disparity cues, vergence and Listing's plane rotate immediately and consistently among subjects. Accommodative vergence, the mutual couplings between vergence and accommodation, can influence the orientation of Listing's plane, but they do so in a idiosyncratic way. The largest rotation was elicited by stereograms combining disparity-vergence with depth perception. These findings support the idea of a functional role of Listing's plane rotation for binocular vision, perhaps for depth perception.

Accommodation, Ocular↗
PubMed1988

The cue interaction model of depth perception: a stability analysis.

In this paper, we offer a stability analysis of "the cue interaction model" of depth perception (House (1984]. Depth estimation using stereopsis suffers from the "matching problem", the problem of correctly matching the retinal image of a feature in one eye, to its retinal image in the other eye. The Cue Interaction Model overcomes this by using monocular cues to disambiguate between the "correct matches" and the "incorrect matches". Its decision making is based on the concept of cooperation and competition in a neural network. A general class of cooperative and competitive models has been mathematically analysed by Amari and Arbib (1977), with special attention given to equilibrium states and stability. In this paper we adapt their methods to study the above model. In particular, we prove that if the parameters are correctly tuned, the model successfully achieves its goals by suppressing the cues which represent the "incorrect matches".

Animals↗
PubMed1981

Depth perception, eye alignment and cortical ocular dominance of dark-related cats.

On first exposure to light, animals that have been reared from birth until about 4 months of age in total darkness exhibit substantial visual and visuomotor deficits, which decline in severity during the first few months following exposure to light. In order to determine whether dark-reared animals eventually acquire stereoscopic vision following exposure to light we examined the binocular status of 5 dark-reared animals two of which developed convergent eye alignment. The binocular status was assessed behaviorally by measurements of the ability of each animal to perceive depth using either one or both eyes, and physiologically by documentation of the distribution of cortical ocular dominance of a sample of visual acuity, their binocular depth perception remained very poor, comparable to the monocular performance of normal cats. In marked contrast to normal animals none of the dark-reared animals, even those with normal eye alignment, performed substantially better binocularly than monocularly, a result indicating the absence of a uniquely binocular mechanism for depth perception in these animals. Although the dark-reared animals were found to retain a substantial (but reduced) complement of binocularly influenced cortical neurons, the tuning of these cells for retinal disparity must be insufficiently precise to mediate depth perception under binocular viewing conditions that is superior to that which can be achieved monocularly.

Animals↗
PubMed2005

Is depth perception of stereo plaids predicted by intersection of constraints, vector average or second-order feature?

Stereo plaid stimuli were created to investigate whether depth perception is determined by an intersection of constraints (IOC) or vector average (VA) operation on the Fourier components, or by the second-order (non-Fourier) feature in a pattern. We first created stereo plaid stimuli where IOC predicted vertical disparity, VA predicted positive diagonal disparity and the second-order feature predicted negative diagonal disparity. In a depth discrimination task, observers indicated whether they perceived the pattern as 'near' or 'far' relative to a zero-disparity aperture. Observers' perception was consistent with the disparity predicted by VA, indicating its dominance over IOC and the second-order feature in this condition. Additional stimuli in which VA predicted vertical disparity were created to investigate whether VA would dominate perception when it was a less reliable cue. In this case, observers' performance was consistent with disparity predicted by IOC or the second-order feature, not VA. Finally, in order to determine whether the second-order feature contributes to depth perception, stimuli were created where IOC and VA predicted positive horizontal disparity while the second-order feature predicted negative horizontal disparity. When the component gratings were oriented near horizontal (+/-83 degrees from vertical), depth perception corresponded to that predicted by the second-order feature. However, as the components moved away from horizontal (+/-75 degrees and +/-65 degrees from vertical), depth perception was increasingly likely to be predicted by an IOC or VA operation. These experiments suggest that the visual system does not rely exclusively on a single method for computing pattern disparity. Instead, it favours the most reliable method for a given condition.

Contrast Sensitivity↗
PubMed2003

A physiological theory of depth perception from vertical disparity.

It has been known since the time of Helmholtz that vertical differences between the two retinal images can generate depth perception. Although many ecologically and geometrically inspired theories have been proposed, the neural mechanisms underlying the phenomenon remain elusive. Here we propose a new theory for depth perception from vertical disparity based on the oriented binocular receptive fields of visual cortical cells and on the radial bias of the preferred-orientation distribution in the cortex. The theory suggests that oriented cells may treat a vertical disparity as a weaker, equivalent horizontal disparity. It explains the induced effect, and the quadrant and size dependence of vertical disparity. It predicts that horizontal and vertical disparities should locally enhance or cancel each other according to their depth signs, and that the effect of vertical disparity should be orientation dependent. These predictions were confirmed through psychophysical experiments.

Depth Perception↗
PubMed1985

Reinstatement of binocular depth perception by amphetamine and visual experience after visual cortex ablation.

In adult cats with bilateral visual cortex ablation the complete deficit in binocular depth perception, as measured on a visual cliff, was reversed by 4 doses of amphetamine. The amphetamine-induced recovery endured after the amphetamine treatment was discontinued. This enduring recovery of function was not obtained if the animals were housed in the dark during drug intoxication. Therefore, both amphetamine intoxication and visual experience are simultaneously required for recovery of binocular depth perception after visual cortex ablation.

Animals↗