Interocular Grouping in Perceptual Rivalry Localized with fMRI.

Bistable perception refers to a broad class of dynamically alternating visual illusions that result from ambiguous images. These illusions provide a powerful method to study the mechanisms that determine how visual input is integrated over space and time. Binocular rivalry occurs when subjects view different images in each eye, and a similar experience called stimulus rivalry occurs even when the left and right images are exchanged at a fast rate.

Dynamic perspective cues enhance depth perception from motion parallax.

Motion parallax, the perception of depth resulting from an observer's self-movement, has almost always been studied with random dot textures in simplified orthographic rendering. Here we examine depth from motion parallax in more naturalistic conditions using textures with an overall 1/f spectrum and dynamic perspective rendering. We compared depth perception for orthographic and perspective rendering, using textures composed of two types of elements: random dots and Gabor micropatterns.

Comparison of stimulus rivalry to binocular rivalry with functional magnetic resonance imaging.

When incompatible images are presented to each eye, a phenomenon known as binocular rivalry occurs in which the viewer's conscious visual perception alternates between the two images. In stimulus rivalry, similar perceptual alternations between rival images can occur even in the midst of fast image swapping between the eyes. Here, we used functional magnetic resonance imaging to directly compare brain activity underlying the two types of perceptual rivalry.

fMRI investigation of monocular pattern rivalry.

In monocular pattern rivalry, a composite image is shown to both eyes. The patient experiences perceptual alternations in which the two stimulus components alternate in clarity or salience. We used fMRI at 3T to image brain activity while participants perceived monocular rivalry passively or indicated their percepts with a task.

How simultaneous is the perception of binocular depth and rivalry in plaid stimuli?

Psychophysical experiments have demonstrated that it is possible to perceive both binocular depth and rivalry in plaids (Buckthought and Wilson 2007, Vision Research47 2543-2556). In a recent study, we investigated the neural substrates for depth and rivalry processing with these plaid patterns, when either a depth or rivalry task was performed (Buckthought and Mendola 2011, Journal of Vision11 1-15). However, the extent to which perception of the two stimulus aspects was truly simultaneous remained somewhat unclear.

Bistable percepts in the brain: FMRI contrasts monocular pattern rivalry and binocular rivalry.

The neural correlates of binocular rivalry have been actively debated in recent years, and are of considerable interest as they may shed light on mechanisms of conscious awareness. In a related phenomenon, monocular rivalry, a composite image is shown to both eyes. The subject experiences perceptual alternations in which the two stimulus components alternate in clarity or salience.

A matched comparison of binocular rivalry and depth perception with fMRI.

Psychophysical experiments have demonstrated that it is possible to simultaneously perceive binocular depth and rivalry in plaids (A. Buckthought & H. R.

Hysteresis effects in stereopsis and binocular rivalry.

Neural hysteresis plays a fundamental role in stereopsis and reveals the existence of positive feedback at the cortical level [Wilson, H. R., & Cowan, J.

Interaction between binocular rivalry and depth in plaid patterns.

Binocular rivalry was studied using plaids which were the sum of orthogonal diagonal gratings plus identical vertical gratings in the two eyes. The rivalry alternations sped up as the spatial frequency difference between the vertical and diagonal gratings was increased above about one octave, but slowed down for smaller differences. The interaction between depth and rivalry was studied using similar plaids but with depth introduced in the vertical components.

Stereoscopic depth discrimination with contrast windowed stimuli.

Depth discrimination with a shifted contrast window was compared to that with a fixed contrast window. Stereoscopic performance with the fixed window was limited to small disparities and varied with spatial frequency. Performance with the shifted window extended to larger disparities and was more similar for low and high spatial frequencies.