Perceived motion in complementary afterimages: verification of a neural network theory

Abstract

Steady fixation of a regular pattern like a bar grating or concentric circles leads to a complementary afterimage at pattern offset. The afterimage has the appearance of shimmering lines that are locally orthogonal to the orientations of the inducing image. Additionally, the afterimage includes motion running parallel to the orientation of the afterimage lines. We argue that this afterimage motion supports the existence of a cue to motion that is based on the spatial organization of oriented responses. This cue was previously proposed after analysis of a neural network model of visual perception. We test predictions of the model on various types of complementary afterimage inducing stimuli. When a contrast or size gradient is included in the inducing image, the afterimage motion moves toward the higher part of the gradient, in agreement with the model. Implications of this cue for computational and neurophysiological theories of motion perception are discussed.

Perceived motion in orientational afterimages: direction and speed

“…A second set of experiments verifies that the rebound trail is used not only as a cue for motion direction, but also for motion speed. In combination with the results in Kim and Francis (2000) these results provide strong evidence for the theory's explanation of CAI motion and provide external validity of many aspects of the theory's mechanisms.…”

“…As in the experiments of Kim and Francis (2000), the goal of this experiment was to create an inducing stimulus that would produce a CAI pattern of responses among orientationally tuned cells that mimics the rebound responses created by a moving stimulus. If the visual system is sensitive to this pattern as a cue to motion, then the CAI should include a corresponding motion percept.…”

“…Recent findings in Kim and Francis (2000) demonstrate that the direction of CAI movement can be controlled by introducing inhomogeneity in the inducing image. In the case of an oriented bar grating, Kim and Francis showed that gradual changes in bar intensity or bar size from one side to the other produced a CAI with motion in the direction of the most intense or largest bar.…”

“…The gradient of response strength along the line indicates the direction of the movement, and the length of the line gives a relative indication of the movement speed. Kim and Francis (2000) suggested that CAIs include a motion after-effect because they produce a pattern of responses among orientationally tuned cells that is similar to the pattern produced by a rebound trail when a stimulus actually moves. Furthermore, they showed that by introducing an intensity or size gradient among a grating's bars, the CAI motion was in a direction toward the most intense or largest bar.…”

Interactions of afterimages for orientation and color: Experimental data and model simulations

“…In the overall design of the BCS, this rebound activity acts as a reset signal to curtail persisting neural signals. The properties of this gated dipole have been used to account for many properties of dynamic vision, including visual persistence (Francis, 1999;Francis et al, 1994) and motion perception (Francis & Grossberg, 1996b;Francis & Kim, 1999, 2001Kim & Francis, 1998, 2000. Neurophysiologicalevidence has been found for gated dipoles in general (Abbot, Varela, Sen, & Nelson, 1997) and for an orientation-based gated dipole in particular (Ringach, Hawken, & Shapley, 1997).…”