Showing papers on "Monocular vision published in 1993"

Fusion of monocular cues to detect man-made structures in aerial imagery

Abstract: The detection and delineation of man-made structures visible in aerial imagery is an important problem for automated cartography, land-use analysis, and thematic mapping. It is also a complex computer vision problem that requires locating regions in imagery that possess properties distinguishing them as man-made objects in the scene, as opposed to naturally occurring terrain features. Current techniques take advantage of structural knowledge to produce building hypotheses. It is reasonable, however, to assume that no single detection method will correctly delineate or verify buildings in every scene. In this paper we introduce a cooperative-methods paradigm for information fusion that is shown to be highly effective in improving the system performance over that achieved by individual building extraction methods. We apply a fusion technique to the symbolic data generated by four monocular building extraction systems in both monocular and stereo image data sets. A set of performance evaluation metrics is developed, described, and applied to the fusion results, and several detailed analyses are presented.

Responses of pigeon vestibulocerebellar neurons to optokinetic stimulation. II. The 3-dimensional reference frame of rotation neurons in the flocculus

Abstract: 1. The complex spike activity of Purkinje cells in the flocculus in response to rotational flowfields was recorded extracellularly in anesthetized pigeons. 2. The optokinetic stimulus was produced by a rotating "planetarium projector." A light source was placed in the center of a tin cylinder, which was pierced with numerous small holes. A pen motor oscillated the cylinder about its long axis. This apparatus was placed above the bird's head and the resultant rotational flow-field was projected onto screens that surrounded the bird on all four sides. The axis of rotation of the planetarium could be oriented to any position in three-dimensional space. 3. Two types of responses were found: vertical axis (VA; n = 43) neurons responded best to visual rotation about the vertical axis, and H-135i neurons (n = 34) responded best to rotation about a horizontal axis. The preferred orientation of the horizontal axis was at approximately 135 degrees ipsilateral azimuth. VA neurons were excited by rotation about the vertical axis producing forward (temporal to nasal) and backward motion in the ipsilateral and contralateral eyes, respectively, and were inhibited by rotation in the opposite direction. H-135i neurons in the left flocculus were excited by counterclockwise rotation about the 135 degrees ipsilateral horizontal axis and were inhibited by clockwise motion. Thus, the VA and H-135i neurons, respectively, encode visual flowfields resulting from head rotations stimulating the ipsilateral horizontal and ipsilateral anterior semicircular canals. 4. Sixty-seven percent of VA and 80% of H-135i neurons had binocular receptive fields, although for most binocular cells the ipsilateral eye was dominant. Binocular stimulation resulted in a greater depth of modulation than did monocular stimulation of the dominant eye for 69% of the cells. 5. Monocular stimulation of the VA neurons revealed that the best axis for the contralateral eye was tilted back 11 degrees, on average, to the best axis for ipsilateral stimulation. For the H-135i neurons, the best axes for monocular stimulation of the two eyes were approximately the same. 6. By stimulating circumscribed portions of the monocular receptive fields of the H-135i neurons with alternating upward and downward largefield motion, it was revealed that the contralateral receptive fields were bipartite. Upward motion was preferred in the anterior 45 degrees of the contralateral field, and downward motion, was preferred in the central 90 degrees of the contralateral visual field.(ABSTRACT TRUNCATED AT 400 WORDS)

Independent effects of lighting, orientation, and stereopsis on the hollow-face illusion.

Abstract: Three experiments were conducted to investigate factors contributing to the ‘hollow face’ illusion. A novel method was employed in which the distance from the mask at which the illusion became apparent or disappeared, when retreating or approaching, respectively, was taken as a measure of the strength of the illusion. In all the experiments an effect of direction of observer's movement was found, demonstrating the stability of the initial percept.Upright orientations were compared with inverted ones to investigate if the illusion reflects a bias towards a familiar percept. The direction of lighting was also varied. Independent main effects of orientation and lighting were found to be consistent with preferences both for upright faces and for top lighting. However, inverted faces also produced the illusion to some extent, suggesting a general preference for convexity. The role of stereopsis in resolving the illusion was tested by comparing monocular with binocular viewing conditions. Monocular viewing cond...

Binocular enhancement of visual acuity

Abstract: Using a computerized test system, we compared binocular and monocular visual optotype acuity, varying both contrast and contrast disparity between the two eyes. When contrast was the same in the two eyes, binocular acuity was better than best monocular acuity by an average of 0.045 log minimum angle of resolution, or 11%. When contrast differed in the two eyes, binocular acuity in most but not all cases was still better than the monocular acuity of the eye that received the higher contrast. This binocular advantage became smaller but remained significant as contrast disparity became larger. These results are most simply explained by threshold contrast summation of high-spatial-frequency letter components.

Vertical-horizontal illusion: One eye is better than two

Abstract: The vertical-horizontal illusion is the tendency for observers to overestimate the length of a vertical line relative to a horizontal line that has the same length. One explanation of this illusion is that the visual field is elongated in the horizontal direction, and that the vertical-horizontal illusion is a kind of framing effect (Kunnapas, 1957a, 1957b, 1957c). Since the monocular visual field is less asymmetric than the combined visual field, this theory predicts that the illusion should be reduced with monocular presentation. This prediction was tested in five experiments, in which the vertical-horizontal illusion was examined in a variety of situations--including observers seated upright versus reclined 90 degrees, monocular presentation with the dominant versus the nondominant eye, viewing in the dark versus in the light, and viewing with asymmetrical frames of reference. The illusion was reliably reduced with monocular presentation under conditions that affected the asymmetry of the phenomenal visual field.

Responses of Pigeon Vestibulocerebellar Neurons to Optokinetic Stimulation. I. Functional Organization of Neurons Discriminating Between Translational and Rotational Visual Flow

Abstract: 1. Extracellular recordings were made from 235 neurons in the vestibulocerebellum (VbC), including the flocculus (lateral VbC), nodulus (folium X), and ventral uvula (ventral folium IXc,d), of the anesthetized pigeon, in response to an optokinetic stimulus. 2. The optokinetic stimuli consisted of two black and white random-dot patterns that were back-projected onto two large tangent screens. The screens were oriented parallel to each other and placed on either side of the bird's head. The resultant stimulus covered the central 100 degrees x 100 degrees of each hemifield. The directional tuning characteristics of each unit were assessed by moving the largefield stimulus in 12 different directions, 30 degrees apart. The directional tuning curves were performed monocularly or binocularly. The binocular directional tuning curves were performed with the direction of motion the same in both eyes (in-phase; e.g., ipsi = upward, contra = upward) or with the direction of motion opposite in either eye (antiphase; e.g., ipsi = upward, contra = downward). 3. Mossy fiber units (n = 17) found throughout folia IXa,b and IXc,d had monocular receptive fields and exhibited direction selectivity in response to stimulation of either the ipsilateral (n = 12) or contralateral (n = 5) eye. None had binocular receptive fields. 4. The complex spike (CS) activity of 218 Purkinje cells in folia IXc,d and X exhibited direction selectivity in response to the large-field visual stimulus moving in one or both visual fields. Ninety-one percent of the cells had binocular receptive fields that could be classified into four groups: descent neurons (n = 112) preferred upward motion in both eyes; ascent neurons (n = 14) preferred downward motion in both eyes; roll neurons (n = 33) preferred upward and downward motion in the ipsilateral and contralateral eyes, respectively; and yaw neurons (n = 40) preferred forward and backward motion in the ipsilateral and contralateral eyes, respectively. Within all groups, most neurons (70%) showed an ipsilateral dominance. 5. For most binocular neurons (91%), the maximum depth of modulation occurred with simultaneous stimulation of both eyes, compared with monocular stimulation of the dominant eye alone. For the translation neurons (descent and ascent), binocular inphase stimulation produced the maximum depth of modulation, whereas for the rotation neurons (roll and yaw), binocular antiphase stimulation produced the maximum depth of modulation. 6. There was a clear functional segregation of the translation and rotation neurons.(ABSTRACT TRUNCATED AT 400 WORDS)

An Examination of the Effects of Axis Foreshortening, Monocular Depth Cues, and Visual Field on Object Identification:

Abstract: Four experiments are reported on the identification of line drawings of common objects. In each experiment, performance on “unconventional” views of the objects, in which the major axis of the obje...

Depth perception in motion parallax and stereokinesis.

Abstract: Perceived depth in the stereokinetic effect (SKE) illusion and in the monocular derivation of depth from motion parallax were compared. Motion parallax gradients of velocity can be decomposed into 2 components: object- and observer-relative transformations. SKE displays present only the object-relative component. Observers were asked to estimate the magnitude and near-far order of depth in motion parallax and SKE displays. Monocular derivation of depth magnitude from motion parallax is fully accounted for by the perceptual response to the SKE, and observer-relative transformations absent in the SKE are of perceptual utility only as determinants of the near-far signing of perceived sequential depth. The amount of depth and rigidity perceived in motion parallax and SKE displays covaries with the projective size of the stimuli. The monocular derivation of depth from motion is mediated by a perceptual heuristic of which the SKE is symptomatic.

Design and performance of trish, a binocular robot head with torsional eye movements

Abstract: We present the design of a controllable stereo vision head. TRISH (The Toronto IRIS Stereo Head) is a binocular camera mount, consisting of two fixed focal length color cameras with automatic gain control forming a verging stereo pair. TRISH is capable of version (rotation of the eyes about the vertical axis so as to maintain a constant disparity), vergence (rotation of each eye about the vertical axis so as to change the disparity), pan (rotation of the entire head about the vertical axis), and tilt (rotation of each eye about the horizontal axis). One novel characteristic of the design is that each camera can rotate about its own optical axis (torsion). Torsional movement makes it possible to minimize the vertical component of the two-dimensional search which is associated with stereo processing in verging stereo systems.

A New VEP System for Studying Binocular Single Vision in Human Infants

Abstract: Visual evoked potentials (VEPs), that provide unequivocal objective evidence of cortical binocularity have been recorded from adults and young infants using a new VEP system developed for this purpose. The system uses alternating field stereoscopy (AFS) to present separate visual stimuli to each eye. With this system, the binocular image pairs to the right and left eyes alternate at a high rate on a single video monitor. The subject wears spectacles incorporating light-scattering liquid crystal lenses which alternate electronically between opaque and clear modes in synchrony with the video monitor. To detect cortical binocularity, the system analyzes VEP activity mathematically and identifies significant responses at test frequencies reflecting binocular cortical interactions exclusively. Three types of binocular stimuli were presented: (1) dynamic random dot correlograms (correlograms); (2) dynamic random dot stereograms (stereograms); and (3) dichoptic checkerboard stimuli. The correlograms are generated when moving random dot patterns presented to each eye alternate between two phases, correlated and anticorrelated. With the stereograms, portions of random dot patterns presented to each eye are shifted horizontally relative to each other at a fixed rate, alternately producing crossed and uncrossed binocular disparities. Subjectively, these patterns appear to shift in depth. Dichoptic checkerboard stimuli are regular checkerboard patterns which reverse at different rates (frequencies) for each eye. Binocular VEPs are generated due to cortical interactions at the difference (beat) frequency. Using this VEP system, we have recorded binocular VEPs from 10 normal adults and more than 40 infant subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Visual servoing of the manipulator using the stereo vision

Abstract: Presents a new method of visual servoing using stereo vision to control the position and orientation of the manipulator with respect to an object. Conventional visual servoing techniques using monocular vision need a priori knowledge such as a model of the object or a parameter of distance to calculate a fixed image Jacobian matrix. This requirement is unnatural from a practical point of view. Moreover, a fixed image Jacobian matrix tends to slow the speed of convergence down. Using stereo vision makes it possible to calculate the exact image Jacobian matrix at any position without using a model of the target object, and results in better convergence characteristics. Both simulation and experimental results are presented to demonstrate the effectiveness of this method. >

An Experimental Study on the Objective Measurement of Accommodative Amplitude under Binocular and Natural Viewing Conditions

Abstract: OTAKE, Y., MIYAO, M., ISHIHARA, S., KASHIWAMATA, M., KONDO, T., SAKAKIBARA, H. and YAMADA, S. An Experimental Study on the Objective Measurement of Accommodative Amplitude under Binocular and Natural Viewing Conditions. Tohoku J. Exp. Med., 1993, 170 (2), 93-102 - A high resolution optometey makes it possible to measure changes in refractive power objectively using reflected light from the fundus of the eye. There are limitations in that the subject has to see the target monocularly through a hole in the instrument. In the present study, we attempted to measure the accommodation and pupillary response with a newly developed device as a means to measure these factors in both binocular and natural viewing conditions. We compared the subjective accommodative amplitude levels obtained from the near-point distance with those of objective accommodative amplitude obtained in earlier studies using a monocular internal target. The amplitude of accommodation of the cases with binocular, natural viewing conditions was approximately 0.7 D larger than with monocular, internal target gazing. In previous studies, the difference between the subjective amplitude of accommodation and the results of the objective measurements, had been reported to be approximately 2 D, and was explained by the depth of focus. However, the difference between the subjective and objective amplitude of accommodation under binocular, natural viewing was smaller than that between the subjective and objective measurements (under monocular internal target gazing) from previous studies. This leads us to believe that besides the depth of the focus, we should consider the fact that the advantageous conditions inherent in binocular, natural viewing may increase the amplitude of accommodation. In the measurement of accommodative amplitude, the use of objective measuring methods are not affected by the subjects' subjective judgement. - accommodation; aging; binocular vision; monocular vision; optometry

Three-dimensional organization of optokinetic responses in the rabbit.

Abstract: 1. Three-dimensional rotations of both eyes were measured in alert rabbits during optokinetic stimulation about axes lying in the horizontal plane or about an earth-vertical axis, with either one or both eyes viewing the stimulus. Optokinetic stimulus speed was 2 degrees /s, either continuous or alternating in polarity (triangular stimulus). In addition to the gains of the responses, the orientations of the response axes relative to the stimulus axes were determined. 2. In comparison to the response to constant-speed optokinetic stimulation about the vertical axis, the response to constant-speed optokinetic stimulation about horizontal axes was characterized by the lack of a speed buildup. In many cases, slow phase tracking was good as long as the eye was within the central oculomotor range but deteriorated when eye deviation became more eccentric and fast phases failed to be generated. These features suggest that the optokinetic reflex about horizontal axes functions as a position-control system, rather than as a velocity-control system. 3. Binocular optokinetic stimulation at constant speed (2 degrees/s) about the roll axis (0 degrees azimuth horizontal axis) elicited disconjugate responses. Although the gain of the response was not significantly different in the two eyes (0.38 for downward and 0.44 for upward stimulation), the response axes of the two eyes differed by as much as 51 degrees. 4. Monocular, horizontal axis optokinetic stimulation at constant speed elicited responses that were grossly dissociated between the two eyes. The magnitude of the responses was anisotropic in that it varied with the azimuthal orientation of the stimulus axis; the maximum gain for each eye (0.41 for the seeing and 0.33 for the covered eye) was at 135 degrees azimuth for each eye. The axis orientation and direction (sense of rotation) of the optokinetic stimulus eliciting the maximal response for each eye coincided with the optic flow normally associated with the maximal excitation of the corresponding ipsilateral anterior canal. 5. Binocular, triangular optokinetic stimulation with small excursions (+/- 10 degrees), which avoided the saturation problems of constant-speed stimulation, elicited adequate responses without systematic directional asymmetries. Gain was approximately 0.9 for all stimulus axis orientations in the horizontal plane. 6. During monocular stimulation with triangular stimuli, the response of the seeing eye showed a gain of approximately 0.5 for all orientations of the stimulus axis. In contrast, the covered eye showed anisotropic responses, with a maximum gain of approximately 0.5 during stimulation of the seeing eye about its 45 degree axis.(ABSTRACT TRUNCATED AT 400 WORDS)

Tonic interocular suppression, binocular summation, and the visual evoked potential.

Abstract: Purpose. Psychophysical studies have shown that a dark-adapted eye exerts a tonic interocular suppression (TIS) upon spatial vision mediated by the contralateral eye. The present study was designed to demonstrate TIS by means of visual evoked potential (VEP) procedures. Methods. Evoked cortical potentials were obtained in response to reversing checkerboard patterns with fundamental Fourier frequencies between 3 and ] 2 cycles per degree. Responses were obtained under monocular viewing conditions when the contralateral "adapting" eye was dark adapted, under monocular viewing conditions when the adapted state of the adapting eye was experimentally manipulated, or under binocular viewing conditions. Data were collected from three healthy young men, two naive regarding purpose of experimentation. Results. Regardless of spatial frequency, monocular responses evoked by stimulating a "test eye" were always smaller in amplitude when the contralateral adapting eye was dark adapted than when adapted to a dim, homogeneous field. The monocular evoked response obtained in the presence of an interocular adapting field was similar in amplitude to the binocular evoked response. During dark adaptation of the contralateral adapting eye, the amplitude of the monocular evoked response decreased: the time course of this decline follows that of psychophysically measured rod thresholds in the directly adapted eye. Conclusions. TIS is easily demonstrated by means of VEP as well as psychophysical procedures. The well-known increase in VEP amplitude resulting from binocular viewing may be attributable to the removal of TIS rather than to "physiologic, binocular summation." Invest Ophthalmol Vis Sci. 1993;34:2443-2448.

The Stereoscope and Photographic Depiction in the 19th Century

Abstract: tion of the role of the interocular discrepancy for binocular space perception. Prior to his researches, several individuals had observed an essential component of Wheatstone's innovation: in binocular vision, the two eyes receive slightly different images.2 Kepler and Descartes had surmised that the muscular sensations arising from the convergence of the eyes in binocular vision might play a role in measuring the proximity of objects." But Wheatstone was the first to propose that the mind fathoms visual space by combining the information from a pair of two-dimensional, monocular pictures. "It being thus established," Wheatstone wrote, "that the mind perceives an object of three dimensions by means of the two dissimilar pictures projected by it on the two retinae, the following question occurs: What would be the visual effect of simultaneously presenting

Image processing apparatus

Abstract: PURPOSE:To measure the three-dimensional position and the like of a body by using one image pickup device, and picking up the similar image so that the viewing difference due to monocular vision is eliminated. CONSTITUTION:A zoom lens 2, which expands and reduces the image, is attached to a TV camera 1 for picking up an image. The image having the parallax for the same object are obtained by changing the focal distance of the zoom lens and picking up the image. A body 8 is measured based on this image and each focal distance at the time when the image is picked up.

Keeping an Eye on the Brain: The Role of Visual Experience in Monkeys and Children

Abstract: The quality of visual experience during infancy determines the functional sensitivity and precision of the mature primate visual system. Infant monkeys subjected to monocular form deprivation show a period of critical visual development that, though decreasing in sensitivity, lasts throughout the first 2 years of life. Photopic threshold spectral sensitivity appears to have a briefer critical period, which is essentially complete by 6 months old, whereas scotopic visual functions appear well developed by 3 months old. Binocular visual functions seem to have the longest period of sensitivity to abnormal visual experience because periods of monocular form deprivation initiated during the first 2 years affect visual functions. Viewing the world through prisms, which mimics the condition of strabismus, causes a permanent loss of cortical binocular cells and stereopsis in monkeys. This result explains stereoblindness in children having equivalent clinical histories.

Parvalbumin immunoreactivity in the lateral geniculate nucleus of rhesus monkeys raised under monocular and binocular deprivation conditions

Abstract: Newborn rhesus monkeys were raised under monocular (lid suture, aphakia, aphakia corrected optically with contact lenses, and occlusion with opaque occluder lenses) and under binocular visual deprivation conditions (aphakia combined with occlusion or optical undercorrection of the fellow eye). Routine immunohistochemical methods with an antibody to the calcium-binding protein paravalbumin (PV) were used to examine the distribution of PV+ neurons and PV+ processes in the LGN of these monkeys. Under all rearing conditions, we found no obvious difference in PV density in neurons in any lamina, although in all monocularly deprived and in two of the three binocularly deprived monkeys neurons connected to the deprived eye were of reduced size. Furthermore, PV-immunoreactive processes in the neuropil of deprived laminae were as numerous and of the same morphologies as those in nondeprived laminae or as in normal controls. Thus, in the LGN of rhesus monkeys, the calcium-binding protein paravalbumin is resistant to monocular as well as binocular visual deprivation during the postnatal maturation process of the visual system.

Long-Term Dysfunctions of Neural Stereoscopic Mechanisms After Unilateral Extraocular Muscle Proprioceptive Deafferentation

Abstract: 1. Neural correlates of the permanent deficits in depth perception that occur when extraocular muscle proprioceptive (EMP) afferents are interrupted unilaterally in kittens were investigated by performing extracellular recordings in the primary visual cortex (area 17) in adulthood. Unilateral section of the ophthalmic branch of the trigeminal nerve (V1 nerve) were performed in 11 cats when they were between 5 and 12 weeks of age (uni-V1 group). Electrophysiological results were compared with those obtained in 17 normal adult cats (control group). 2. Binocular interactions were assessed by testing the sensitivity of cortical neurons to dichoptic presentations of moving sine-wave gratings whose interocular positional phase relationship was randomly varied. The amplitude modulation between the minimum and the maximum binocular responses defined the dynamic range. The degree of binocular suppression or facilitation was assessed by comparing these binocular response limits with the optimal monocular responses evoked through either eye at the best spatial frequency. The variability of both monocular and binocular responses was estimated by using the variation coefficient. 3. In uni-V1 cats, both the dynamic range and the degree of binocular suppression were significantly less pronounced than in controls, whereas binocular facilitation was not affected. The variability of the binocular responses was significantly increased, unlike monocular responses, whose variability was similar to control values. 4. From Fourier analysis of the poststimulus time histograms, two clear-cut categories of cells emerged that were differentially affected in the uni-V1 group. The "modulated" cells showed significantly less binocular suppression than in controls, and the "unmodulated" cells had binocular responses that were significantly more variable than in controls. Results from "simple" cells were similar to those of modulated cells, and results from "complex" cells were similar to those of unmodulated cells. However, in the unmodulated population, which was composed of both simple and complex cells, it was shown that the increase of variability was due to that of complex cells. 5. A nonparametric statistical test was applied on the interocular phase shift tuning curves to determine the minimum stimulus change necessary to elicit a significant change in the neural response. Two categories of cells were determined: the "discriminative" cells (80% in controls but 45% in uni-V1 cats) combined pronounced binocular suppression and dynamic range with relatively low variability. The reverse was true in the case of "nondiscriminative" cells (20% in controls and 55% in uni-V1 cats). 6. In uni-V1 cats, about half of the cells were monocularly activated.(ABSTRACT TRUNCATED AT 400 WORDS)

Tylec optical occluders for correcting double vision

Abstract: There is provided an apparatus for treating individuals suffering from binocular diplopia. The apparatus comprises a frame, having first and second viewing lenses, and includes a mechanism for supporting the frame in an operative position relative to the individual such that the first and second lenses are in front of the left and the right eyes respectively. Each eye of the individual is considered as having a range of vision defined by left and right fields of view. A first occluding device is associated with the first viewing lens, for occluding at least a portion of the right field of view of the left eye. A second occluding device is associated with the second viewing lens, for occluding at least a portion of the left field of view of the right eye. In this arrangement, monocular vision is substantially achieved alternately between the left and right eyes as the eyes scan to the left and right respectively. Methods for treating an individual suffering from monocular and binocular diplopia are also contemplated by the present invention. One such method includes (1) supporting first and second lenses in an operative position relative to the individual such that the first and second lenses are located in front of the first and second eyes of the individual respectively; and (2) occluding an intended line of sight of the first eye by affixing an occluder onto the first lens. Monocular vision is achieved over a complementary line of sight of the second eye.

Visual alignment from the midline: a declining developmental trend in normal, strabismic, and monocularly enucleated children.

Abstract: Children, 1.8 to 5.0 years of age, were asked to sight through a tube at targets. There were three groups tested: children with normal binocular vision, children with strabismus, and children with one eye enucleated. The younger normal and strabismic patients placed the tube midway between the two eyes. Surprisingly, the younger enucleated children also placed the tube at the midline. This "Cyclops effect" diminished as the children grew older, with a transition to sighting monocularly by the age of 4 years. The tendency to align with the midline by the younger children, regardless of the degree of their binocular vision, presumably is a natural response to a cyclopean projection center in the midline. As children mature, they learn to meet the demands of monocular preference tasks by aligning objects in front of one eye.

Monocular and binocular neuronal activity in human visual cortex revealed by electrical brain activity mapping.

Abstract: In the present study, we investigated topographical differences between monocularly and binocularly evoked potential fields related to the retinal location and spatial frequency of grating stimuli. Electrical brain activity was recorded in 18 healthy adults using an array of 21 electrodes over the occipital areas. Vertical black-and-white grating patterns of different spatial frequencies were presented with central fixation or lateralized to the left or right hemiretina. Computation of global field power determined component latency. Topographic characteristics of the field distributions were examined at the individual component latency for each subject using statistical comparisons between experimental conditions. The strength of the potential fields was significantly larger with binocular stimuli, whereas no effects were observed when comparing component latencies. Pronounced differences occurred in the spatial distribution of electrical brain activity: with 2.5 cycles/deg, large, significant topographic differences between monocularly and binocularly evoked activity were obtained. The potential fields showed a more anterior and more lateralized component distribution with binocular than monocular stimuli. In addition, when the gratings were presented binocularly, significant topographic differences were observed when low and high spatial frequency stimuli were compared. Our results suggest that the relationship between the topography of evoked components and retinal stimulus location and spatial frequency is different for monocular and binocular stimuli, indicating that binocular information processing triggers different neuronal processes in the human visual cortex.

Monocular and Dichoptic Interactions between Moving and Stationary Stimuli

Abstract: Visual motion of a physically stationary stimulus can be induced by the movement of adjacent stimuli. The frequencies of motion reports and the angular separations required to induce motion were determined for a number of stimulus configurations. A stationary stimulus was fixated in the centre of the display and the point at which induced motion was initially reported was measured. In the first experiment either one or two stationary stimuli were presented in the centre of a display and either one or two similar stimuli moved horizontally towards them. The percentage of trials on which motion was induced varied with the display configuration, being greatest with two moving and one stationary stimuli. The angular separations at which motion was reported were about 2 deg for all conditions. In the second experiment the binocular interaction of such induced motion was examined. A single static fixation stimulus was presented binocularly and a range of monocular or dichoptic conditions was examined: a single moving stimulus to one eye, two moving stimuli to one eye, or two moving stimuli dichoptically. Induced motion was reported on about 90% of the trials for the monocular and dichoptic conditions with two moving stimuli. Motion was first induced at similar angular separations by two moving stimuli, whether presented monocularly or dichoptically. Binocular interaction was further examined with a display that induced motion in the stimulus presented to one eye but not in that presented to the other: this resulted in the apparent motion in depth of the binocularly fixated stimulus.

Der Bewegungsnacheffekt als Analyseinstrument des visuellen Systems

Abstract: In several experiments the motion after-effect as elicited by spirals and gratings (waterfall displays) is used to analyze the processing of information within the visual system. The duration and judged strength of after-effects are determined with respects to different fixation conditions (monocular and binocular fixation conditions as well as centric and excentric conditions). The results show that motion after-effects in spirals and waterfall displays are generated and processed in different ways within the visual system. The results are discussed on the basis of a metric of the visual system by means of the motion after-effect.

Apparent Motion Perception: The Contribution of the Binocular and Monocular Systems. An Improved Test Based on Motion Aftereffects

Abstract: Research concerning the perception of apparent motion is not easy to conduct: it is hard to obtain quantitative results that can be easily interpreted A solution to this problem is the use of motion aftereffects (MAEs) Adapting subjects to a specific type of motion leads to apparent motion in the opposite direction when the stimulus is removed However, subjects are aware of the change in stimulus conditions A new dynamic test stimulus is proposed in order to avoid artefacts introduced by the awareness of the conditions by the subject A model, derived from earlier observations, is described which includes contributions from monocular and binocular systems Results from an experiment in which the dynamic test stimulus was used show that they do not necessarily reproduce the results obtained with a static test stimulus Central monocular systems are added to the model to account for this discrepancy The ‘pooling hypothesis’, which states that the MAE is a weighted mean of the processes involved, permit

Cyclopean stereo vision for depth perception

Abstract: In human binocular vision, the two retinal images are unified into a single image with perception of depth through a mechanism called 'binocular sensory fusion'. The term cyclopean vision refers to the unified visual scene of the world obtained from fusion of the images projected to the two eyes. This paper describes an algorithm which simulates the fusion process for depth perception. The disparity information of the entire image is obtained by a convolution operation followed by a local maxima detection. The computation burden, and therefore, the processing time, is largely reduced.

Paradoxical monocular stereopsis and perspective vergence

Abstract: The question of how to most effectively convey depth in a picture is a multifaceted problem, both because of potential limitations of the chosen medium (stereopsis, image motion), and because effectiveness can be defined in various ways. Practical applications usually focus on information transfer, i.e., effective techniques for evoking recognition of implied depth relationships, but this issue depends on subjective judgements which are difficult to scale when stimuli are above threshold. Two new approaches to this question are proposed here which are based on alternative criteria for effectiveness. Paradoxical monocular stereopsis is a remarkably compelling impression of depth which is evoked during one-eyed viewing of only certain illustrations; it can be unequivocally recognized because the feeling of depth collapses when one shifts to binocular viewing. An exploration of the stimulus properties which are effective for this phenomenon may contribute useful answers for the more general perceptual problem. Positive vergence is an eye-movement response associated with changes of fixation point within a picture which implies depth; it also arises only during monocular viewing. The response is directionally appropriate (i.e., apparently nearer objects evoke convergence, and vice versa), but the magnitude of the response can be altered consistently by making relatively minor changes in the illustration. The cross-subject agreement in changes of response magnitude would permit systematic exploration to determine which stimulus configurations are most effective in evoking perspective vergence, with quantitative answers based upon this involuntary reflex. It may well be that most effective pictures in this context will embody features which would increase effectiveness of pictures in a more general sense.