Binocular Vision

Talk Session: Tuesday, May 23, 2023, 8:15 – 9:45 am, Talk Room 2
Moderator: Johannes Burge, University of Pennsylvania

Talk 1, 8:15 am, 51.21

Vergence anomalies are associated with impaired stereopsis in the central visual field

Aidan Gauper1 (), Suzanne McKee1, Dennis Levi2, Preeti Verghese1; 1Smith-Kettlewell Eye Research Institute, 2UC Berkeley

Previously we mapped stereopsis across the visual field and showed that local stereopsis is impaired in the central visual field for individuals with known stereo deficits due to anisometropia or microstrabismus, while peripheral stereopsis was spared. As disparity drives fusional vergence responses, we hypothesized that the residual sensitivity to coarse disparities in the near periphery likely drives fusional vergence eye movements. Furthermore, if stereopsis in the central foveal region is impaired, then the fusional vergence response to a small stimulus confined to the near foveal region will be reduced. We used binocular eye tracking (Eyelink 1000 in the table-mount configuration), to measure the vergence response to a disparity step as the difference in the right and left eye position signals. We measured vergence as a function of stimulus configuration and the size of the disparity step. The disparity step occurred on 3 configurations: a large disc 16°in diameter, a small disc 4° in diameter, and an annulus with outer and inner diameters corresponding to the large and small discs. After the observer aligned nonius lines, a key press initiated the disparity step that lasted 3 seconds. Individuals with anisometropia or microstrabismus (n=3) had low vergence gain for small stimuli, that sometimes increased to near normal levels for larger stimuli, consistent with abnormal stereopsis in the central visual field. Among controls with no history of amblyopia or strabismus (n=8), those with intact local stereopsis across the visual field had vergence gains near 1, for all stimulus sizes (n=4). However, the remaining observers were stereoanamolous in the central visual field, and had abnormal fusional vergence. These abnormalites were either transient (could be made normal with increased effort) or remained persistent. These results suggest that the stereo-deficiency in the central retina is associated with poor fusional drive.

Acknowledgements: NIH Grant 1R01EY034370

Talk 2, 8:30 am, 51.22

Retinal eccentricity strongly modulates how interocular delays are impacted by image differences

Callista Dyer1, Johannes Burge1,2,3; 1University of Pennsylvania, 2Neuroscience Graduate Group, University of Pennsylvania, 3Bioengineering Graduate Group, University of Pennsylvania

The temporal properties of visual processing vary with the stimulus being processed and its projected retinal location. Here, we present data with sub-millisecond resolution showing that retinal eccentricity strongly modulates how quickly retinal images are processed. We show that changes in luminance (and blur) cause large changes in the speed of visual processing and, crucially, that these effects are modulated — up to a factor of ten — by where on the retina the signals are processed. To compare temporal processing in the retinal periphery to that in the fovea, we developed a novel stimulus that leverages the Pulfrich effect, a classic illusion caused by processing delays between the eyes. The stimulus was a dichoptically presented set of eight white circular beads, arranged in a circle, which rotated clockwise or counter-clockwise around the circle’s center at a constant angular velocity. Luminance (or blur) differences between the eyes induced interocular processing delays. These delays made the rotating beaded circle appear slanted either top-back or bottom-back with respect to the screen. The task was to fixate the circle’s center and report which type of slant was perceived. We probed processing at five eccentricities ranging from 0.5deg to 6.0deg by changing the circle’s radius. The speed of movement (1 to 12deg/sec) and the size of each circular bead (10 to 120arcmin) scaled with the radius. Seven-level psychometric functions were collected, with onscreen delay as the independent variable. The data shows that substantially larger delays occur near the fovea than in the periphery for a given interocular image difference. We discuss why eccentricity-dependent processing implies the existence of a temporal binding mechanism, and detail the resultant perceptual consequences when the temporal binding problem is incorrectly resolved. The results highlight the severe computational challenge of obtaining stable percepts of the environment with a temporally-variant retina.

Acknowledgements: This work was supported by NIH grant R01-EY028571 from the National Eye Institute and the Office of Social and Behavioral Science

Talk 3, 8:45 am, 51.23

Does contrast adaptation influence the Pulfrich phenomenon?

Aymen Sahal1, Alexandre Reynaud1, Robert Hess2; 1Department of Opthalmology and Visual Sciences, McGill University, 2McGill Vision Research Unit

The Pulfrich phenomenon is the visual illusory perception of motion-in-depth caused by a monocular reduction of luminance. Recently we showed that such illusion could also be caused after short-term monocular deprivation or “patching”, presumably caused by a monocular contrast-gain change. Therefore, to investigate this mechanism further, in this study we wanted to determine if it is possible to induce the Pulfrich phenomenon through contrast adaptation. We used a 3D passive screen using 3D glasses to adapt each eye to high contrast separately and display the Pulfrich stimulus. In each trial, participants were exposed to a 3-second-long contrast-adapting stimulus followed by structure-from-motion defined rotating cylinder made of Gabor patches. Adaptator contrast was 100% and stimulus contrast was either 100% or 15%. The differences between the right-eye-adapted and left-eye-adapted points of subjective equality (PSE) were then used to reveal the occurrence of the Pulfrich phenomenon. The results support the idea that adapting one eye to high contrast creates an interocular delay as the PSE values differed significantly after each eye adaptation. All the PSEs arising from left eye adaptation were significantly higher than those from right eye adaptation (p<0.001 for both 100% and 15% stimulus contrast), indicating a link of causation between which eye gets adapted and the direction of the phase shift. Furthermore, the gaps between the PSE values increased when reducing the contrast level of the Gabor patches from 100% to 15% (p<0.001). Contrast adaptation seems to influence the Pulfrich phenomenon through a unilateral increase in visual processing, creating an interocular delay. This finding hints at a key relationship between contrast gain control and the Pulfrich phenomenon.

Acknowledgements: I would like to thank the support provided by the Mr. & Mrs. John Henry Collis Memorial Bursary for making this summer research experience possible.

Talk 4, 9:00 am, 51.24

Coarse-to-fine interaction on perceived depth in compound grating

Pei-Yin Chen1 (), Chien-Chung Chen1,2, Shin'ya Nishida3,4; 1Department of Psychology, National Taiwan University, 2Center for Neurobiology and Cognitive Science, National Taiwan University, Taipei, Taiwan, 3Department of Intelligence Science and Technology, Graduate School of Informatics, Kyoto University, 4NTT Communication Science Laboratories, Nippon Telegraph and Telephone Corporation

The visual system encodes binocular disparity with either a position or a phase offset between the left and the right eye bandpass filters. However, the local disparity measurement of each subband is ambiguous, particularly when the actual disparity is larger than the half-cycle of the preferred spatial frequency of the filter. We investigated whether the visual system uses a coarse-to-fine interaction to resolve this ambiguity at fine scales in estimating depth from disparity. The stimuli were stereo-grating patches composed of a target and a comparison pattern, which were assigned randomly to the upper and lower halves of the stimuli. The target patterns contained both 1 and 4 cycles per degree (cpd) spatial frequencies, and the comparison patterns were either a compound grating with 1 and 4cpd components or a 1cpd simple grating. The phase disparities of both the low- and high-frequency components were independently changed in the range from -90o (uncrossed) to 90o (crossed). The observers’ task was to indicate whether the target or the comparison pattern appeared closer to them. Regardless of whether the comparison patterns were compound or simple gratings, the perceived depth difference between the target and the comparison increased with the phase disparity of the high-frequency component. This effect occurred not only when the low-frequency component was at the horopter, but also when it contained a -90o or 90o disparity, which corresponded to one cycle of the high-frequency component. Such a result implies a coarse-to-fine interaction in the multi-scale disparity processing, in which the depth interpretation of the high-frequency changes with the disparity of the low-frequency component.

Acknowledgements: Supported by MOST(Taiwan) 110-2917-I-564-022 to PYC and by MEXT/JSPS KAKENHI (Japan) 20H00603 and 20H05605 to SN

Talk 5, 9:15 am, 51.25

MEG Reveals Distinct Dorsal and Ventral Streams for Binocular Rivalry Dominance and Suppression

Janine Mendola1 (), Elizabeth Bock2, Jeremy Fesi1, Jason Da Silve Castenheira2, Sylvain Baillet2; 1Department of Ophthalmology and Vision Sciences, McGill University, Montreal, QC H9G 1A4, 2Department of Neurology and Neurosurgery and the McConnell Brain Imaging Centre, Montreal Neurological Institute, McGill University

Binocular rivalry is an example of bistable visual perception extensively examined in neuroimaging. Magneto-encephalography (MEG) can track brain responses to phasic visual stimulations of pre-determined frequency and phase to advance our understanding of perceptual dominance and suppression in binocular rivalry. We used left and right eye stimuli (red and green orthogonal gratings) that flickered at two tagging frequencies (5 and 7.5 Hz) to track their respective oscillatory cortical evoked responses. We computed time-resolved measures of coherence to track the brain responses phase-locked with stimulus frequencies, and with respect to the participants’ indications of alternations of visual rivalry they experienced. Using Brainstorm software, we compared the brain maps obtained to those from a non-rivalrous control replay condition that used physically changing stimuli to mimic rivalry. We found stronger coherence within a posterior cortical network of visual areas during rivalry dominance compared to rivalry suppression and replay control. This network extended beyond the primary visual cortex (V1) to several retinotopic visual areas. In addition, network coherence with dominant percepts in V1 peaked at least 50 ms prior to the suppressed percept nadir; consistent with Wilson’s (2003) escape theory of alternations. Moreover, individual alternation rates were correlated with the rate of change (slope) in dominant evoked peaks, but not for the slope of response to suppressed percepts. This further supports the (escape) theory that a perceptual switch occurs when the suppressed-to-dominant tag increases sufficiently. Finally, an effective connectivity measure (Phase Transfer Entropy) revealed that dominant or suppressed percepts were preferentially expressed in dorsal or ventral stream streams, respectively. We thus demonstrate that binocular rivalry dominance and suppression engage distinct mechanisms and brain networks. These findings advance neural models of rivalry and may relate to more general aspects of selection and suppression in natural vision.

Acknowledgements: This work was supported by a Discovery Grant from NSERC to J.M.; S.B. was supported by an NSERC Discovery Grant, Canada Research Chair of Neural Dynamics of Brain Systems, NIH, Healthy Brains for Healthy Lives Canada Excellence Research Fund, and Brain Canada Foundation Platform Support Grant.

Talk 6, 9:30 am, 51.26

Population models of binocular disparity tuning predict the direction of perceived depth in correlated and anticorrelated random dot stereograms

Paul Hibbard1 (), Jordi Asher1; 1University of Essex

Binocular information is an important cue to depth, and is encoded by disparity-tuned cells in the visual cortex. The responses of these cells depend on their phase-disparity tuning, and the interocular correlation of the stimulus within their receptive field. This has allowed us to develop computational models of how binocular information can be used to estimate depth. One important stimulus manipulation in this context is the anticorrelation of stimuli between the two eyes, in which the contrast polarity of elements in one eye is reversed. This results in an inversion of the disparity tuning function of binocular neurons. It is typically assumed that this should result in a reversal of their preferred disparity, and the direction of depth perceived in anticorrelated stimuli. The effect of anticorrelation for individual neurons will however depend on their position and phase tuning, and the spatial frequency of their disparity tuning function. By modelling the disparity tuning functions of populations of neurons we confirm that the preferred disparity does tend to be in opposite directions for correlated and anticorrelated stimuli, but with wide variation in the relationship between two. We also show that a model of disparity-tuning functions in the human visual system predicts a reversal in the direction of depth perceived in anti-correlated stimuli, but a greatly reduced ability to discriminate depth magnitude. We also show how the influence of the second-order disparity channel predicts the perception of forward depth in some anticorrelated stimuli, such as simple Gaussian blobs and step edges in anticorrelated stimuli. We conclude that the modelling of the disparity tuning properties of real cortical neurons, and how these are combined in the estimation of disparity, allows us to make clear quantitative predictions about the perception of depth, and the roles of phase and position encoding of disparity in this process.