Binocular single vision achieved by fusion and suppression

The occurrences of fusion and suppression were determined from stereograms which produced two retinal images located at equal distances but in opposite directions from the fovea. Subjects reported whether the dichoptic stimulus appeared single or not, and if single whether it appeared in the center of the visual field. The report of centrality is predicted by the fusion theory of single vision and that of noncentrality by the suppression theory. Experiment 1, with eight subjects, showed that for small disparities perceived singleness was the percept predicted by the fusion theory; for larger disparities, the percepts could sometimes be predicted by the fusion theory and other times by the suppression theory. Experiment 2, with 16 subjects, showed that with larger stimuli the percept predicted by the fusion theory is more likely to occur. Experiment 3, with four subjects, showed that the centrality was reported when the stimuli were presented for 100 msec. This result provided support for our interpretation that the centrality reports in Experiments 1 and 2 were not due to fixation error and suppression.     

Binocular fusion: A test of the suppression theory

Binocular fusion may be due to interocular inhibitory suppression, an hypothesis difficult to evaluate by phenomenal inspection. A test probe method (reaction time to a light pulse) was used to measure visual sensitivity during binocular rivalry and fusion. The absence of inhibitory effects during fusion fai Is to support the suppression theory of fusion.     

Binocular fusion: A test of the suppression theory

Binocular fusion may be due to interocular inhibitory suppression, an hypothesis difficult to evaluate by phenomenal inspection. A test probe method (reaction time to a light pulse) was used to measure visual sensitivity during binocular rivalry and fusion. The absence of inhibitory effects during fusion fails to support the suppression theory of fusion.     

Thought-action fusion and thought suppression in obsessive-compulsive disorder.

To examine the significance of thought-action fusion (TAF) and thought suppression tendencies, the present study obtained pre- and post-treatment questionnaire data on these constructs in a sample of OCD patients (n=24) and non-OCD anxiety patients (n=20). Results indicate that TAF and suppression are correlated with severity of psychopathology. Yet, the associations between TAF and psychopathology are not typical for OCD, but do also occur in other anxiety disorders (e.g., panic disorder, post traumatic stress disorder, and social phobia). As well, mean scores on the TAF and thought suppression measures dropped significantly from pre- to post-treatment, indicating that TAF and thought suppression are susceptible to change during psychotherapy.     

Binocular rivalry and surface-boundary processing

Theoretical and empirical studies show that the visual system relies on boundary contours and surface features (e.g. textures) to represent 3-D surfaces. When the surface to be represented has little texture information, or has a periodic texture pattern (grating), the boundary contour information assumes a larger weight in representing the surface. Adopting the premise that the mechanisms of 3-D surface representation also determine binocular rivalry perception, the current paper focuses on whether boundary contours have a similar role in binocular rivalry. In experiment 1, we tested the prediction that the visual system prefers selecting an image/figure defined by boundary contours for rivalry dominance. We designed a binocular rivalry stimulus wherein one half-image has a boundary contour defined by a grating disk on a background with an orthogonal grating orientation. The other half-image consists solely of the (same orientation) grating background without the grating disk, ie no boundary contour. Confirming our prediction, the predominance for the half-image with the grating disk is approximately 90%, despite the fact that the grating disk corresponds to an area with orthogonal grating in the fellow eye. The advantage of the grating disk is dramatically reduced to about 50% predominance when a boundary contour is added to the background-only half-image at the location corresponding to the grating disk. We attribute this reduced advantage to the formation of a corresponding binocular boundary contour. In experiment 2 the grating background was substituted by a random-dot background in a similar stimulus design. We found that the perceptual salience of the corresponding binocular boundary contours extracted by the interocular matching process is an important factor in determining the dynamics of binocular rivalry. Experiment 3 showed that vertical lines with uneven thickness and spacing as the background reduce the contribution of the monocular boundary contour of the grating disk in binocular rivalry, possibly through the formation of binocular boundary contours between the local edges (vertical components) of the vertical lines and the corresponding grating disk.     

Binocular rivalry and visual awareness

Physiological studies of binocular rivalry have provided important clues to the relationship between neural activity in the brain and visual awareness. However, uncertainty about these insights has been raised by a recent study showing that the events underlying binocular rivalry occur earlier in the visual pathway than was previously thought.     

Binocular rivalry and immediate memory

Three experiments examine features of a simple memory task on which right-handed, right eye dominant subjects have been reported to recall digits projected to the right eye more accurately than those projected simultaneously to the left eye. Superior recall by these subjects of information projected to the right eye was observed only when stimuli projected simultaneously to both eyes were seen as overlapped in the binocular percept. Under monocular presentations, accurracy of recall was not related to the eye with which stimuli were viewed. The binocular oveslap condition has a significance other than that of simply increasing the difficulty of identifying the elements in a visual display for there were no differences in accuracy of recall from each eye when overlapped stimuli were viewed monocularly. More accurate recall of right eye information appears to reflect the resolution of a conflict between inputs from each eye. The possible relation of this finding to cerebral dominance is also discussed. Order of recall in these experiments depended mainly on spatial cues provided by the experimental situation.     

Binocular rivalry and reciprocal inhibition

Any explanation of binocular rivalry based on a reciprocal inhibition mechanism would require that unilateral increases in the stimulus strength of the rivalry target in one eye produce increases in the mean nonsuppression duration of that eye and concommitant decreases in the mean nonsuppression duration of the contralateral eye. To test that hypothesis, the stimulus strength (in this case, contrast) of one rivalry target was varied (0.1, 1, 10, and 100 ft-L) while the strength of the target in the other eye remained constant. The data, obtained from six experienced Ss, indicate that variations in stimulus strength do not alter the mean nonsuppression duration of the recipient eye. This outcome offers a fundamental difficulty for the reciprocal inhibition concept. A model that assumes partially independent suppression and dominance mechanisms is suggested as a more adequate alternative.     

基于双眼视差的立体视觉去掩蔽效应

基于双眼视差的立体视觉不改变目标与掩蔽刺激之间的信噪比, 但能使不同的刺激被知觉在不同的深度位置上以降低目标信号所受到的掩蔽作用。本综述在总结前人双眼去掩蔽研究的基础上, 强调深度维度上的视觉注意在这种主观空间分离去掩蔽过程中所起的重要作用, 并介绍了双眼去掩蔽在现代科技领域中的典型性应用。最后, 结合听觉主观空间分离去掩蔽的研究进展, 本综述认为主观空间分离去掩蔽是大脑处理复杂刺激场景的一个基本功能。     

双眼竞争研究现状与展望

双眼竞争是指当双眼所呈现的图像不一致而无法形成单一、稳定的知觉进而造成知觉动态交替变化的现象,其研究已有近200年的历史,至今仍是神经科学、心理学、生理学和临床医学中的研究热点。该文阐述了双眼竞争的概念、常用测量指标;总结了双眼竞争的特点及对双眼竞争的影响因素;讨论了双眼竞争与其他形式的多稳态知觉间的关系。行为实验、脑成像和电生理实验分别揭示了双眼竞争的早期加工模型和晚期加工模型的不足之处,Tong等人综合各方面的实验结果提出了双眼竞争的多层次–混合加工理论模型,这一模型将早期加工和晚期加工模型有机地结合起来,对于研究视觉意识的神经机制具有重要的理论指导意义。在总结已有研究的基础上,该文明确指出了双眼竞争的可应用领域及未来的研究方向     

Binocular rivalry and stereoscopic depth perception

An investigation was made of stimulus factors causing retinal rivalry or allowing stereoscopic depth perception, given a requisite positional disparity. It is shown that similar colour information can be “filtered” out from both eyes; that stereopsis is not incompatible with rivalry and suppression of one aspect of the stimulus, and that the strongest cue for perception of stereoscopic depth is intensity difference at the boundaries of the figures in the same direction at each eye. Identity of colour can also act as a cue for stereopsis. The brightness of different monocular figures seen in the stereoscope in different combinations was estimated by a matching technique, and it is suggested that the perceived brightness is a compromise between the monocular brightness difference between figure and ground seen in relation to the binocular fused background, and the mean brightness of the figures. The results are discussed in terms of neurophysiological “on,” “off” and continuous response fibres.     

Binocular interactions in flicker

Sherrington's (1904) study of binocular flicker was extended by measuring observers' sensitivity to light that was modulated sinusoidally at frequencies between 0·1 and 50 Hz. Compared with the condition in which both eyes are stimulated in-phase, about 40% more modulation is needed to detect high-frequency flicker when the two eyes are stimulated in counterphase; at low frequencies this difference is even greater. These results suggest that the earlier c.f.f. studies underestimate the amount of binocular interaction in the detection of flicker.     

Binocular foveation in reading

We present a theory of foveation in normal binocular reading. We consider the pervasive, nontrivial binocular fixation disparities (FDs) observed in reading and relate them to the computational problem of resolving retinal disparities in depth perception. We infer that the right eye's fixation being to the right of the left eye's in reading promotes binocular fusion in challenging conditions. We then show a different (nonfusional) processing advantage for the right eye's fixation being to the left of the left eye's in reading conditions in which binocular fusion is assured, by modeling the combined influence of foveal splitting, contralateral preference, ocular prevalence, and fixation disparity. This synthesis of anatomically grounded research in different aspects of visual processing produces a theory of foveation in reading that matches current data and makes testable predictions.     

Relationships between thought-action fusion, thought suppression and obsessive-compulsive symptoms: a structural equation modeling approach

Research has shown that there are strong similarities in content between the obsessions and compulsions that characterize obsessive-compulsive disorder and nonclinical obsessions and compulsions. However, clinical and nonclinical obsessions and compulsions do differ with respect to characteristics like frequency, intensity, discomfort and elicited resistance. Two separate concepts have been invoked to explain how normal obsessions and compulsions may develop into clinical phenomena. First, it is suggested that thought-action fusion (TAF) contributes to obsessive-compulsive symptoms. Second, thought suppression may intensify obsessive-compulsive symptoms due to its paradoxical effect on intrusive thoughts. Although both phenomena have been found to contribute to obsessive-compulsive symptoms, possible interactions between these two have never been investigated. The current study explored how TAF and thought suppression interact in the development of obsessive-compulsive symptoms. Undergraduate psychology students (N = 173) completed questionnaires pertaining to TAF, thought suppression and obsessive-compulsive symptoms. Covariances between the scores on these questionnaires were analyzed by means of structural equation modeling. Results suggest that TAF triggers thought suppression, while thought suppression, in turn, promotes obsessive-compulsive symptoms.     

Binocular detection by normal and stereoblind observers

Binocular forced-choice detection performance was measured in three stereoblind observers and four observers with normal stereopsis. Detection rates of normal observers were greater than expected from probability summation, while those of the stereoblind observers were near or at a level expected from probability. It is concluded that binocular summation is reduced or absent in stereoblind persons.     

Binocular rivalry and the contrast at contours

Binocular rivalry was recorded between various achromatic figures in or near the foveae. For a pair of intersecting contours, one in the field of each eye, it was found that the percentage of time for which a contour was dominant at the point of intersection increased with the contrast at that contour, and also with average luminance when contrast was constant. Further, for 1° circles in corresponding positions in the two fields, one darker than its surround and one lighter, the same results were obtained. Various auxiliary results, on rate of rivalry, eye-dominance, the occasional mixture of the rivalling stimuli, and binocular lustre, are given. Finally the relationship between predominance in rivalry and perceived brightness is discussed.