When motion is not perceived: Evidence from adaptation and dynamical stability

Abstract

Adaptation was used to probe the perceiver's activation state when either motion or nonmotion percepts are formed for bistable, single-element apparent motion stimuli. Although adaptation was not observed in every instance, when it was observed its effect was to increase the probability of both motion-to-nonmotion and nonmotion-to-motion switches, the time scale of adaptation corresponding to neurophysiological observations for directionally selective cortical cells (Giaschi et al. 1993). This susceptibility to de-stabilizing adaptation effects indicated that the nonmotion percept was not the result of inadequate stimulation producing subthreshold levels of motion detector activation; if that were the case, activation-dependent adaptation would have decreased the nonmotion-to-motion switching rate by reducing activation further below threshold. Above-threshold activation levels are therefore associated with both nonmotion and motion perceptual states, and the failure to perceive motion despite the presence of adequate motion detector stimulation can be attributed to inhibitory competition between detectors activated by motion-specifying stimulus information and detectors activated to similar levels by motion-independent stimulus information, consistent with the dynamical quality of single-element apparent motion.

Linking dynamical perceptual decisions at different levels of description in motion pattern formation: Computational simulations

“…In addition, there is psychophysical evidence with apparent motion stimuli for the adaptation of detectors responsive to motion-specifying stimulus information (Anstis, Giaschi, & Cogan, 1985;Hock, Nichols, & Espinoza, 2004), as well as adaptation of detectors responsive to motion-independent spatial information (Hock et al, 2004). Variables representing the effects of adaptation are therefore coupled with each of the V1 and MT activation variables.…”

Linking dynamical perceptual decisions at different levels of description in motion pattern formation: Psychophysics

“…It is assumed that the percept is embodied in those detectors whose activation is stabilized at values above the threshold level required for perception. Hock, Kogan, and Espinoza (1997) and Hock, Nichols, and Espinoza (2004) have provided psychophysical evidence that detectors responsive to motion-independent spatial information compete with motion detectors in determining whether motion or nonmotion is perceived. They observed spontaneous switching between nonmotion and motion percepts, motion/nonmotion hysteresis, and the independent adaptation of perceived nonmotion and perceived motion.…”