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

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

“…Our evidence that the level of feedforward activation affects pattern stability therefore supports the hypothesized activation dependence of these future-shaping interactions. The computational plausibility of this conclusion is supported by the dynamical simulations presented in the article that follows (Nichols et al, 2006).…”

“…Psychophysical results in this article and computational simulations of these results in the accompanying article (Nichols, Hock, & Schöner, 2006) indicate that (1) pattern-level hysteresis depends on activation-dependent detector interactions and, therefore, on the magnitude of the activation that feeds forward from local to pattern levels, and (2) local-level dynamical decisions that result in motion or nonmotion being perceived (i.e., local bistability) affect pattern-level dynamical decisions by feeding forward different magnitudes of activation for the same stimulus. Dynamical decisions occur when the activation levels of stimulated detectors are attracted to and maintained near stable, fixed-point values (Hock, Schöner, & Giese, 2003), where each fixed point represents the joint activation state of all detectors relevant to the percept.…”

“…The key to the experiments here and the computational simulations in the accompanying article (Nichols et al, 2006) is the activation dependence of future-shaping interactions. When the activation transmitted from the local to the pattern level is relatively low, future-shaping interactions are expected to be weak; horizontal motion can be perceived, but the vertical motion detectors that will be stimulated in the immediate future would be only weakly inhibited.…”

The temporal dynamics of global-to-local feedback in the formation of hierarchical motion patterns: psychophysics and computational simulations

“…In a subsequent computational study, Nichols, Hock, and Schöner (2006) found that distinguishing between different levels of processing is necessary in order to account for the effects of luminance perturbations on the stability of the parallel-path motion pattern perceived for the motion quartet. Hock and Ploeger (2006) had shown that depending on whether the luminance perturbations increased or decreased the activation of local motion detectors, the stability of the parallel-path motion perceived for the motion quartet either increased or decreased.…”

“…At the higher level, inhibitory competition between detectors that respond selectively to horizontal motion and detectors that respond selectively to vertical motion determines whether parallel-path horizontal or parallel-path vertical motion is perceived. Nichols et al's (2006) two-level model is entirely feedforward. It is consistent with evidence that area V1 motion detectors with the same directional selectivity converge onto larger area MT receptive fields with that directional selectivity (Kohn & Movshon, 2003;Movshon & Newsome, 1996).…”