Attention-biased multi-stable surface perception in three-dimensional structure-from-motion

Abstract

Retinal velocity distributions can lead to a percept of three-dimensional (3D) structure (structure-from-motion [SFM]). SFM stimuli are intrinsically ambiguous with regard to depth ordering. A classic example is the orthographic projection of a revolving transparent cylinder, which can be perceived as a 3D cylinder that rotates clockwise and counterclockwise alternately. Prevailing models attribute such bistable percepts to inhibitory connections between neurons that are tuned to opposite motion directions at equal binocular disparities. Cylinder stimuli can yield not only two but as many as four different percepts. Besides the well-documented clockwise and counterclockwise spinning transparent cylinders, observers can also perceive two transparent half-cylinders, either convex or concave, one in front of the other. Observers are able to bias the time during which a percept is present by attending to one or the other percept. We examined this phenomenon quantitatively and found that in standard SFM stimuli, the percept of two convex transparent half-cylinders can occur just as often as the percept of (counter-) clockwise spinning cylinders. So far, however, all interpretations of experimental (neurophysiological) data and all proposed mechanisms for SFM perception have focused solely on the two classical cylinder percepts. Prevailing models cannot explain the existence of the other two percepts. We suggest an alternative model to explain attention-biased multi-stable perception.

Multisensory Congruency as a Mechanism for Attentional Control over Perceptual Selection

“…We deliberately designed the rotation rate to be different from the looming sound rate so that their changes over time did not match. Following previous attentional studies of unisensory ambiguous perception, we examined voluntary control over visual rivalry by comparing "active" and "passive" conditions (Helmholtz, 1866;Lack, 1978;Peterson and Hochberg, 1983;Leopold and Logothetis, 1999;Suzuki and Peterson, 2000;Hol et al, 2003;Toppino, 2003;Meng and Tong, 2004;Chong et al, 2005;Slotnick and Yantis, 2005;van Ee et al, 2005van Ee et al, , 2006Brouwer and van Ee, 2006;Chong and Blake, 2006;Hancock and Andrews, 2007). In the passive condition, no attentional control was exerted in favor of either visual pattern.…”

Human Middle Temporal Cortex, Perceptual Bias, and Perceptual Memory for Ambiguous Three-Dimensional Motion

“…Due to a lack of additional depth cues indicating which motion direction corresponded to the front, and which to the back surface of the globe, observers alternately perceived either rotation direction (Braunstein, 1977). Less commonly, the same stimulus may in some cases be perceived as two "half-spheres" that both point outward toward the observer while sliding in opposite directions, one behind the other (Hol et al, 2003). Although our observers did not spontaneously report this perception, we preempted any confusion it might cause by instructing observers to report the motion direction of the surface perceived to be in front, regardless of whether the hind surface was convex or concave.…”

Visual Cortex Allows Prediction of Perceptual States during Ambiguous Structure-From-Motion

“…During the main ambiguous sphere experiments, subjects viewed an ambiguous sphere continuously for 200 s. They were instructed to strictly fixate the central dot and to press one button when the front surface reversed from a rightward to a leftward direction [clockwise (CW)] and another button when the opposite occurred [counterclockwise (CCW)]. Subjects can also perceive the stimulus as two convex surfaces or two concave surfaces (Hol et al, 2003); however, they still perceive one surface to be in front of the other, meaning that they could still do the task. Scanning started 20 s after the start of the experiment to remove any stimulus onset-specific activation.…”

“…Such stimuli can be made perceptually bistable: ambiguously rotating spheres, perceived to rotate in opposite directions (Treue et al, 1991;Andersen and Bradley, 1998;Hol et al, 2003). Exploiting its ambiguous nature, single-cell studies found correlations between MT activity and perceived direction Dodd et al, 2001).…”