Non-corresponding Points Research Articles

Alfred Wilhelm Volkmann on stereoscopic vision

ABSTRACT Wheatstone’s demonstration of binocular single vision and depth with stimulation of non-corresponding points reverberated throughout mid-nineteenth century German visual science. It challenged the received view that single vision was a consequence of retinal correspondence otherwise objects were seen double. Wheatstone also argued that stimulation of corresponding points could yield double vision. He interpreted his experimental observations in psychological rather than physiological terms, as did Helmholtz later. Volkmann addressed both of these challenges in a long article on stereoscopic vision published in 1859. While he accepted the first of the questions Wheatstone posed Volkmann was more cautious with regard to the second. Volkmann was an experimentalist who applied psychophysical methods to determine thresholds for stereoscopic depth perception. In line with many of his colleagues in Germany, he took issue implicitly with Wheatstone’s approach: how can the detailed quantitative experiments supporting Vieth and Müller’s interpretation of binocular single vision be derailed by simple observations with a stereoscope? Unlike most of his colleagues, Volkmann was swayed in Wheatstone’s favor through his own experiments: both physiological and psychological processes are involved in stereoscopic depth perception.

Interocular Suppression in Primary Visual Cortex in Strabismus.

People with strabismus acquired during childhood do not experience diplopia (double vision). To investigate how perception of the duplicate image is suppressed, we raised two male monkeys with alternating exotropia by disinserting the medial rectus muscle in each eye at age four weeks. Once the animals were mature, they were brought to the laboratory and trained to fixate a small spot while recordings were made in primary visual cortex (V1). Drifting gratings were presented to the receptive fields of 500 single neurons for eight interleaved conditions: (1) right eye monocular; (2) left eye monocular; (3) right eye's field, right eye fixating; (4) right eye's field, left eye fixating; (5) left eye's field, right eye fixating; (6) left eye's field, left eye fixating; (7) both eyes' fields, right eye fixating; (8) both eyes' fields, left eye fixating. As expected, ocular dominance histograms showed a monocular bias compared with normal animals, but many cells could still be driven via both eyes. Overall, neuronal responses were not affected by switches in ocular fixation. Individual neurons exhibited binocular interactions, but mean population indices indicated no net interocular suppression or facilitation. Even neurons located in cortex with reduced cytochrome oxidase (CO) activity, representing portions of the nasal visual field where perception is suppressed during binocular viewing, showed no net inhibition. These data indicate that V1 neurons do not appear to reflect strabismic suppression and therefore the elimination of diplopia is likely to be mediated at a higher cortical level.SIGNIFICANCE STATEMENT In patients with strabismus, images fall on non-corresponding points in the two retinas. Only one image is perceived, because signals emanating from the other eye that convey the duplicate image are suppressed. The benefit is that diplopia is prevented, but the penalty is that the visual feedback required to adjust eye muscle tone to realign the globes is eliminated. Here, we report the first electrophysiological recordings from the primary visual cortex (V1) in awake monkeys raised with strabismus. The experiments were designed to reveal how perception of double images is avoided.

Deformation Field and Acoustic Emission Characteristics of Weakly Cemented Rock under Brazilian Splitting Test

Weakly cemented rocks are widely distributed in the Shendong Mining Area, and their mechanical properties and deformation characteristics have a significant influence on disaster prevention and the design of roadway excavation. This study investigated the evolution of the deformation field, acoustic emissions (AEs) and energy of four common weakly cemented rocks under Brazilian splitting test, and the relationship among the three parameters was discussed. The results show that the evolution of the coefficient of variation (Cv) in different rocks was similar and can be divided into two fast declining stages, a fluctuating rising stage and a sharply rising stage. There was a sudden increase in the cumulative AE energy before the peak strength was reached, which was positively correlated with the development of penetrating cracks. The evolution of Cv, growth rate of dissipated energy (Gd) and AE counts was consistent with the stress state, while there were some ‘non-corresponding points’ during the deformation and failure process. In addition, Cv, Gd and AE counts were more sensitive to deformation and failure characteristics than stress. The research findings provide basic parameters and a reference for predicting dynamic disasters in the Shendong Mining Area.

Natural statistics of depth edges modulate perceptual stability.

Binocular fusion relies on matching points in the two eyes that correspond to the same physical feature in the world; however, not all world features are binocularly visible. Near depth edges, some regions of a scene are often visible to only one eye (so-called half occlusions). Accurate detection of these monocularly visible regions is likely to be important for stable visual perception. If monocular regions are not detected as such, the visual system may attempt to binocularly fuse non-corresponding points, which can result in unstable percepts. We investigated the hypothesis that the visual system capitalizes on statistical regularities associated with depth edges in natural scenes to aid binocular fusion and facilitate perceptual stability. By sampling from a large set of stereoscopic natural images with co-registered distance information, we found evidence that monocularly visible regions near depth edges primarily result from background occlusions. Accordingly, monocular regions tended to be more visually similar to the adjacent binocularly visible background region than to the adjacent binocularly visible foreground. Consistent with our hypothesis, perceptual experiments showed that perception tended to be more stable when the image properties of the depth edge were statistically more likely given the probability of occurrence in natural scenes (i.e., when monocular regions were more visually similar to the binocular background). The generality of these results was supported by a parametric study with simulated environments. Exploiting regularities in natural environments may allow the visual system to facilitate fusion and perceptual stability when both binocular and monocular regions are visible.

3-D Deep Feature Construction for Mobile Laser Scanning Point Cloud Registration

Due to errors in sensors and positioning, there exist mismatches between different phases of mobile laser scanning point clouds, which impede the application of point cloud, such as changing detection and deformation monitoring. To rectify such mismatches, we designed a 3-D deep feature construction method for point cloud registration. The proposed method combines two 3-D convolutional neural networks into a uniform deep learning model to extract 3-D deep features. First, the corresponding points and noncorresponding points are set to train the deep learning model to minimize the distance between corresponding points’ features and maximize the distance between features of noncorresponding points. Second, in the test phase, the 3-D deep feature for each keypoint was extracted by the trained deep learning model. This could be used to determine the corresponding points by the $k$ -dimensional tree and random sample consensus (RANSAC) algorithm. Finally, a transformation matrix was calculated based on the corresponding points and was then applied to point cloud registration. The experimental results illustrated that the proposed method of using 3-D deep features is more efficient at a corresponding point search than representatives of three existing methods. It also improved registration accuracy.

Hemiretinal Trigger Mechanism-Reply

In Reply. —We would like to thank Dr Campos for his interesting remarks. It is difficult, to be sure, with any test in patients with a monofixation syndrome and peripheral fusion, whether this fusion is on normally corresponding points or abnormally corresponding points (ARC). The reason for this is that the error of the tests is often greater than the few prism diopters of deviation present in these patients. The two patients with ARC mentioned in our article had convergent angles of 18 diopters and 20 prism diopters, respectively, at the test distance and, hence, we could be more certain that fusion, in the periphery, was occurring on noncorresponding points in the deviating eye. We think that the other points raised by Dr Campos have been covered in our article.